ap401 apple orchard system design and productivity...
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AP401 Apple orchard system design and productivity
Simon Middleton and Alan McWaters QLD Department of Primary Industries
AP401
This report is published by the Horticultural Research and Development Corporation to pass on information concerning horticultural research and development undertaken for the apple and pear industry.
The research contained in this report was funded by the Horticultural Research and Development Corporation with the financial support of the apple and pear industry.
All expressions of opinion are not to be regarded as expressing the opinion of the Horticultural Research and Development Corporation or any authority of the Australian Government.
The Corporation and the Austrahan Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests.
Cover price: $20.00 HRDC ISBN 1 86423 745 7
Published and distributed by: Horticultural Research & Development Corporation Level 6 7 Merriwa Street Gordon NSW 2072 Telephone: (02)9418 2200 Fax: (02) 9418 1352 E-Mail: [email protected]
© Copyright 1998
H R D V C
HORTICULTURAL RESEARCH & DEVELOPMENT CORPORATION
Partnership in horticulture
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS 3
INDUSTRY SUMMARY 4
TECHNICAL SUMMARY 5
INTRODUCTION 6
MATEmALS AND METHODS 8
(i) Flatbed solarimeters 8
(a) Theory of the approach 8
{b) Design of flatbed solarimeters 9
(c) Use of flatbed solarimeters and 'solid models' in the field 11
(ii) Light penetration and distribution within apple trees 13
(a) The measurement of light. 13
(b) Field trial sites 16
RESULTS 19
(i) Flatbed solarimeters 19
(ii) Light penetration and distribution within apple trees 26
DISCUSSION 38
CONCLUSIONS AND I^COMMENDATIONS 44
PUBLICATIONS 46
REFERENCES 47
APPENDIX I. FRUIT COLOUR CLASSES 49 APPENDIX II. SAMPLE PRINTOUT OF HOURLY LIGHTMETER
READINGS FROM A DATA LOGGER 50 APPENDIX III. SAMPLE DIURNAL FLATBED SOLARIMETER READINGS
FOR 'SOLID MODEL' DESIGNS 51
ACKNOWLEDGEMENTS
The research presented in this report was jointly funded by the Horticultural Research and Development Corporation and the Australian Apple and Pear Growers Association.
The Queensland Department of Primary Industries (QDPI) also contributed significantly, with the provision of office, laboratory and research station facilities as well as administrative, scientific and technical support staff
The authors wish to gratefully acknowledge the assistance of many people, without whose help the project would not have been possible :
• Marcel Veens and Aldo, Corado and Dino Rizzato (Granite Belt, Qld); Kevin Fraser (Orange, NSW); Peter Amadio (Batlow, NSW); Doug Lees and Jack and John Pottenger (Goulbum Valley, Vic); Roger and Derek Seller (Momington Peninsula, Vic); and Scott Pryce (Ranelagh, Tas) are commercial apple orchardists who all provided orchard sites and maintained and managed apple trees as required in the field trials.
•
•
Ron Gordon, Delia Dray and Jill Campbell (NSW Agriculture); Bill Thomson and John Read (Vic Department of Agriculture); Predo Jotic (Tas Dept of Primary Industry and Fisheries); Paul James (Primary Industries South Australia); and John Sutton and Maurice Bales (WA Department of Agriculture) are officers of State Departments of Agriculture who all provided direct input into the project by contributing advice on local state issues, and/or identifying appropriate orchard trial sites. The officers in Tasmania, South Australia and Western Australia also provided departmental research station facilities for the project, including plots of established apple trees in which light levels were measured, and appropriate open ground for flatbed solarimeter measures.
Chandra Smith, Helen Hall, Megan Walker and Angelina Rowell provided technical assistance at various stages of the project, and assisted with the Queensland fieldwork and in the computer entry and collation of data.
Debbie Rouen and Jillian Turpin typed the final report and the several papers and extension publications generated by this project over the last three years. Angelina Rowell also assisted in the collation of this report.
Special thanks must go to my wife Judy, whose enduring love and patience during my frequent absences and long working hours made the completion of this project possible.
INDUSTRY SUMMARY
Orchard light interception and the distribution of light within the apple tree canopy are the keys to high yields and good fruit quality. The aim in the design, planting and management of any orchard system is to create and maintain a desirable tree form (height, shape, spread, leaf area) that intercepts as much sunlight as possible, whilst allowing light to reach all parts of the canopy.
A good guide to apple orchard productivity is to look at the shadows cast by trees during mid-morning or mid-afternoon on a fine, clear day in December or January. 'Speckling' of light on the orchard floor - small patches of light at regular intervals in the main block of cast shadow - suggests that trees are well-structured, that light is reaching all regions of the canopy, and that yields and fruit quality are high and close to optimum.
If there are numerous patches of light that take up more of the ground area than the shadow, it is likely that tree growth and vigour are too low for high productivity. If the shadow is a solid block with no light reaching the ground, then the trees are too vigorous, with a dense leaf canopy and poor light distribution reducing yield and fruit quality. If the shadow encroaches well onto the adjacent row of trees then the trees are too tall or wide for the designated alley space.
North/south row orientation should always be favoured over east/west. The light interception by east/west rows is only greater than north/south rows late in the season, when light intensities are less and the sun is lower in the sky. This is too late to derive many of the benefits of good light distribution within the tree, such as fruit bud initiation, fiiiitlet development and maximum seasonal photosynthesis. The light that is intercepted by east/west rows is largely on the exposed northern side, with the southern side remaining relatively shaded. If trees are too tall, alleyways too narrow or the leaf canopy too dense, the deficiencies of east/west rows become even more marked. Here, fixiit on the top northern side of the trees is susceptible to sunburn, while on the southern side fniit are of poor size and quality, with low yields produced.
Orchard light interception is increased with taller trees and narrower alleyways, but a point is reached where light distribution in the canopy, and hence yield and fixiit quality, are adversely affected. A 50% increase in tree height from 2.8 to 4.3 metres increases light interception by only six to 10 percent, whereas reducing alley width from six metres to four metres provides a more efficient 14 to 20 percent increase in light interception. Indeed, field measures of light interception, light distribution and apple tree productivity show that throughout Australia, a tree height of approximately 2.8 metres and midseason light interception of 60% should be two key objectives in apple orchard system design for high productivity.
Trees of angled cross-section with a well-defined central leader confined within the row, improve light penetration to lower parts of the canopy. This is the classic 'Christmas Tree' shape, characterised by a shallow canopy at all points. Trees of rectangular cross-section (where growth occurs above and beyond the alley) can intercept more light, however if the canopy is too dense, this is at the expense of light penetration, yield and fruit quality lower in the tree.
TECHNICAL SUMMARY
Orchard productivity as it relates to tree fruit crops is a term that consists of a yield component and a fruit quality component. The reason why one orchard system is more productive than another can be related to the interception and distribution of light in the tree canopy. Light must be intercepted if a tree is to attain its full yield potential, and the adequate penetration of light to all parts of the apple tree canopy is the determinant of fruit quality and final packout.
In this project, a new method to assess the effect of orchard system design and tree 'form' (height, shape, spread, row orientation) effects on light interception was the use of flatbed solarimeters and 'solid models' that simulated a range of orchard systems. This approach produced a core of information, that conventional field trials would normally take up to 10 to 15 years to provide and at considerable cost.
Flatbed solarimeter measures in the apple producing regions of all Australian states, from latitude 28° 37'S at Stanthorpe, Qld in the north to 42°59'S in the Huon Valley, Tasmania in the south, show that in mid-season (January) when the trees are at fiiU leaf, north/south rows always intercept more light than comparable east/west rows. The light interception of east'west rows increases by March/April (harvest) as solar altitude and azimuth decline during autumn, and at harvest is greater than north/south orientations, but this is too late to benefit fruit bud initiation and fruitlet development. If trees are too tall, alleyways too narrow or the leaf canopy too dense, the deficiencies of east/west rows become even more marked, with fruit on the upper northern sides of the rows susceptible to sunburn whilst the southern side can remain relatively shaded and of low productivity.
Maintaining a narrow canopy depth in all directions from which sunlight may be coming is a sound principle that is a feature of many orchard systems. The more leaves there are above or outside a certain point in the canopy, the less likely it is for light to reach that point. Hence, in productive orchards all fiiiit bearing regions of the trees are never far from an outside surface. If the leaf canopy is too dense, even a depth of 30 centimetres can make regions below or behind this unproductive.
Poor yields and finit quality are associated with either insufiicient tree vigour/canopy volume, or excessive tree vigour and resultant shading. Although trees of rectangular cross-section can intercept more light, trees with angled sides, a shallow canopy and a well-defined central leader improve light penetration to regions closer to the ground. This is importtint in apple trees, where excessive internal tree shading will reduce yield, fruit size, colour and TSS. An orchard LAI of 2.0 and a 2:1 ratio of tree height to clear alley width are good guides to high orchard productivity, and minimise deleterious shading effects by maintaining a high volume of 'well-illuminated' canopy that receives at least 40% of incident diurnal sunlight.
Precocious dwarf and semi-dwarf rootstocks for apple have facilitated increased planting densities and heavy cropping within tree to four years of planting. Such rootstocks reduce tree size and increase the canopy volume exposed to adequate light. If, however, rootstocks are too dwarfing, trees have insufficient canopy volume to support high yields and under Australian sunlight intensities may also produce fruit susceptible to sunburn through exposure to radiant heat, unless protected by hail netting.
INTRODUCTION
Australian apple orchards traditionally consisted of vigorous trees trained as a 'vase' and planted 6 metres x 6 metres on the square (280 trees per hectare). A few such 'wide-spaced' orchards still exist today, but are of poor productivity with annual yields as low as 10 tonnes per hectare. Large inter and intra-row spaces between these trees means light interception is low. In addition, tree heights upwards of 4 metres progressively push the more productive, younger wood to the upper regions of tall trees, thereby increasing the costs of pruning and harvesting and contributing to spray coverage problems.
The availability of precocious dwarfing and semi-dwarfing clonal rootstocks that reduce apple tree size has been the catalyst for increased planting densities over the past two decades. The majority of Australian apple orchards are now planted at densities of 800 to 1250 trees per hectare, and generally consist of trees planted 2 to 2.5 metres apart in single-row hedgerows separated by 4 to 5 metre wide tractor alleyways. When inappropriate tree densities and/or rootstocks are used with such designs however, the orchard can largely consist of 'non-productive' alleyways instead of fruit producing surfaces.
A major advantage of intensive systems over traditional wide-spaced orchards is their potential to produce high yields within three to four years of planting, and maintain this productivity over the lifetime of the orchard. This has been especially exploited in Europe where there is widespread adoption of multi-row systems that reduce the orchard area "wasted" by tractor alleyways (Parry, 1981; Jackson et al, 1986). Such high density bed systems (2000+ trees per hectare) require reductions in tree size to ensure all finait receive adequate sunlight levels, and hence utilise dwarf rootstocks such as M9. Experience with these systems in Australia is limited.
Australian apple production occurs between latitudes 28°S and 43°S. Although the ambient sunlight intensities of these latitudes are high relative to other apple-producing regions of the world, many commercial orchards are not attaining their yield and fruit quality potential. The recently completed benchmarking study identified that yields from Australian apple orchards currently average 30 tonnes per hectare (AAPGA, 1996), which is less than many of our international competitors. The use of vigorous rootstocks and training systems inappropriate at higher planting densities can create high levels of shading within intensive orchards, and severely reduce yield and quality.
It is well documented that internal tree shading can reduce yield, fruit size, colour arid TSS (Jackson, 1978; Doud and Ferree, 1980; Morgan e/a/., 1984). Increasing the height of trees in single-row hedgerows can lead to small yield improvements, but the gain is usually at the expense of yield and fruit quality low in the canopy (Jackson and Palmer, 1972; Palmer, 1977). With insufficient light, the crop closer to the ground declines and is of poor quality, and it is not economical to concentrate the cropping zone towards the top of tall trees.
Worldwide over-production of apples has made it uneconomic to produce poor quality fi-uit. Markets most often associate apple quality with fruit appearance characteristics such as size, colour and fi-eedom fi-om blemish, and grading standards are set accordingly. The effects of both external and internal tree shading on fruit quality become extremely important with intensive plantings. System designs must ensure the adequate illumination of a high
proportion of the tree to reduce the volume of "unproductive" canopy producing poor yields and low quality fruit. The advantage of high density orchards in maximising light interception must also extend to optimising light distribution within the canopy if full yield and fruit quality potential are to be realised.
Since orchard productivity is dependent on sunlight interception and the distribution of light within the canopy (Jackson, 1980a), studies of orchard design provide the basis for improvements in light climate, and hence yield and fruit quality. The vinderlying aim in any field trial that compares rootstock, planting density, tree arrangement and tree training effects on yield and fruit quality, is to most closely achieve the tree 'form', canopy volume and leaf area distribution required for optimum light interception and distribution. Light measurements therefore play an important role in the interpretation of results from studies, however funding, labour, time and technical constraints mean that few system comparisons have been made on the basis of measured light interception.
For practicality, any field trials of orchard system design and light interception can only compare a small number of the thousands of potential orchard design options (combinations of rootstock X spacing x training x row orientation x leaf area etc), and will necessarily be restricted to a few of those systems considered most likely to be productive at a local level. Similarly, the time, equipment and expertise necessary to measure the seasonal light interception of several systems simultaneously, restricts the light measures that can be made.
A technique developed at Horticulture Research International, East Mailing, Kent, UK was used as part of this project, to rapidly estimate the light interception of a range of orchard system designs in the field without the need to plant expensive, long-term field trials. 'Solid' scale models representing trees were placed on specially designed and constructed flatbed solarimeters, and the effects of changes in tree density, arrangement, height, shape and row orientation on orchard light interception measured. This approach is described in more detail in the Materials and Methods.
The overall objective of the project was to determine orchard system design and tree management principles to increase the productivity of Australian apple orchards. The project objectives can be subdivided as follows:
• Compare tree 'form' effects (height, spread, shape, alley width, row orientation) on orchard light interception, to determine how best to increase light interception and yields without compromising light distribution and fruit quality.
• Define the optimal tree 'form' that maximises yield and fruit quality under Australian light conditions, thereby providing a vision of an "ideal" tree conformation to aim for in orchard design and management.
• Compare the productivity of a range of orchard systems with respect to seasonal light interception, leaf area index and tree dimensions.
• Use flatbed solarimeters to predict the light interception of a wide range of orchard systems without the need to plant long-term field trials, and consider the implications of these results in the design and management of Australian apple orchards.
• Provide a simple, rapid rule of thumb that can be used by orchardists to visually assess the light interception, light distribution and productivity of apple trees in the field.
MATERIALS AND METHODS
Two approaches were simultaneously used in this project to determine apple orchard system designs appropriate to maximising orchard productivity under Australian light conditions:
- Flatbed solarimeter estimation of orchard light interception.
- Field measurements of light interception and distribution within trees of a range of apple varieties and planting systems.
The two methods are now described in more detail.
(i) Flatbed solarimeters
(a) Theory of the approach
'Solid models' designed to represent a range of orchard systems were placed on flatbed solarimeters in the field, and used to determine tree 'form' effects (tree height, spread, shape, arrangement, planting density, alley width, row orientation) on orchard light interception.
The theory behind this approach is described in detail by Jackson (1980b), Jackson and Middleton (1987) and Middleton (1990). The technique is used to rapidly predict the maximum light that can be intercepted by a particular orchard system.
In brief, light transmission (T) through a discontinuous canopy such as a tree fruit orchard can be considered in terms of two discrete components such that:
T = Tf + T, c
where T is the total light transmitted to the orchard floor; Tf is the light which misses the trees completely and would reach the ground even if the trees were 'solid'; and Tc is the light which passes through the tree canopy (Jackson and Palmer, 1979). Tf is dependent on canopy geometry (tree form), and T^ is dependent on leaf area.
Jackson (1980b) re-defmed the transmission equation in terms of light interception, and presented the derivation in detail to show that:
^ "• max ^ max ^
and Lj = F ax ((111 ly-K) or LAI if this is less
where F is the fraction of available light that is intercepted, V^^^ is the fraction of available light that will be intercepted by non-transmitting trees of a given dimension and arrangement, K is the light extinction coefficient (0.6 for apple), L' is the leaf area per unit potentially shaded orchard surface area (LAI/F^ax), I is the level of irradiance considered as the lower limit for well-illuminated canopy, and Lj is the LAI within this part of the canopy.
These equations permit the rapid determination of light interception and the volume of "well-illuminated" canopy of any orchard design, given knowledge of LAI and F^^ for different orchard systems under the local light conditions, and the minimum light levels required for the satisfactory development of fruit yield and quality. Leaf area index (LAI) is readily measurable, and F^ x can be determined for different orchard systems by designing 'solid', non-transmitting scale models to simulate the appropriate orchard design, and arranging them on a flatbed solarimeter in the field (Middleton and Jackson, 1989).
(b) Design of flatbed solarimeters
The flatbed solarimeters were designed to measure the light that would be transmitted to the orchard floor if trees were considered as solid, non-transmitting structures. Their design and construction are described in detail by Middleton (1990).
In brief, each flatbed solarimeter consisted of a thermopile of copper-constantan junctions connected in series. Copper foil squares measuring 13 mm x 13 mm were bonded onto an expanded polystyrene base to form 14 rows each consisting of 14 squares. Adjacent copper foil squares were separated by a 1 mm gap, and the squares were alternately painted matt black and matt white. The total receptive surface of each thermopile measured 20 cm x 20 cm (400 cm ). The polystyrene base of the thermopile was bonded onto 4 mm thick perspex, and a small spirit level was also mounted on the perspex to ensure level setting of the thermopile in the field.
The centres of each pair of black and white copper foil squares were linked from beneath by 42swg constantan (Eureka) wire laced through holes in the polystyrene and perspex bases. The pairs of copper-constantan jimctions were joined together by a side link of 36 swg tirmed copper wire, and the output connections from the thermopile to the lead-out signal cable were also of 36 swg tinned copper. The thermoelectric output from each pair of copper foil squares was proportional to the temperature difference between the black and white surfaces, which in turn was proportional to the incident radiant flux density.
The electrical output from each flatbed solarimeter was equal to the output of the 98 pairs of copper-constantan junctions connected in series, and was measured with a microvolt integrator (Type MV2, Delta-T Devices).
The perspex supporting the thermopile was screwed into a plastic box measuring 53 x 43 x 22 cm. The sides of each box were covered in aluminium foil to reflect heat (Plate 1), and an aperture in one of the sides allowed the escape of heat from inside the box and prevented the build-up of condensation.
The upper surface covering the thermopile of the flatbed solarimeter consisted of two layers. An air gap separated the thermopile from a sheet of glass to absorb infra-red radiation, and 3 mm above this was a 4 mm thick white perspex diffusive surface. The perspex and glass layers locked tightly onto the box of the flat-bed solarimeter, and the whole unit was watertight.
The flatbed solarimeters responded evenly to irradiance over the area of the perspex diffiiser above the thermopile. This was tested under full sunlight conditions in the field, by covering constant size areas of the perspex and recording the outputs with the microvolt integrators.
Plate 1. The use of flatbed solarimeters in the field to estimate apple orchard light interception, based here on solid models representing a central leader hedgerow system.
The white perspex diffusive surface of each flatbed solarimeter represents the orchard floor, and overlays a thermopile that has been constructed within each flatbed solarimeter box. By using different solid model designs and changing their orientation, the effects of orchard design on light interception can be rapidly assessed.
The FBS on the left measures the light that would reach an orchard floor without trees, and measurements from this permit calculations of light interception by different orchard system designs positioned on the FBS on the right.
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(c) Use of flatbed solarimeters and 'solid models' in the field
Solid scale models painted matt black and made of either wood or 'Plaster of Paris' were designed to represent series of different orchard systems. The models were placed on the perspex diffusing surface of the flatbed solarimeters (Plates 1 and 2), and the electrical outputs from these recorded with microvolt integrators.
One flatbed solarimeter (FBSl) was always used as a control, with no models on the perspex diffusive surface (as in Plate 1). FBSl measured the light that would reach an orchard floor without trees, which is also the same as the incident above tree sunlight levels. Measured electrical output from the FBS with models (FBS2) represented the light transmitted to the orchard floor if the trees of that particular orchard design were 'solid' and non-transmitting (Tf). Maximirai potential orchard light interception (F^ax) was then calculated as 1-Tf or ((FBSl - FBS2)/FBS1) x 100%.
The 'solid' models were designed to encompass a range of different tree heights, spreads and cross-sectional shapes. Variations in the positioning of models allowed comparison of row orientation, alley width, multi-row system, tree arrangement and planting density effects on orchard light interception.
Designs included simple blocks of wood from which the effects of free height, alley width and row orientation on light interception could be rapidly simulated, through to several cenfral leader, conical "Christmas tree" shapes of different heights, spreads and canopy volumes made out of 'Plaster of Paris' (one of these model designs is illustrated in Plate 2). These "cones" were especially suitable for measuring the effects of tree arrangement, planting density, double-row and triple-row systems on light interception, with up to 100 of each scale model made to represent individual trees . Rows of cones could simply be progressively added to simulate increases in tree density and more complicated multi-row systems. Wooden models to simulate Tatura Trellis, Ebro Trellis and Lincoln Canopy were also made.
The procedure followed in the flatbed solarimeter (FBS) estimation of apple orchard light interception was to measure the output from the microvolt integrators over a two minute period for each model design. Following each two minute "run", a new model was put in place, measured for two minutes, replaced by the next model, and so on. Using three FBS, the light interception by a series of up to 24 "solid model" orchard designs could be measured in quick succession. This would occur over a 40 to 45 minute period in every hour of measurement.
Each series of measures was repeated every hour of the cenfral seven to 11 hours of the day (depending on the season) around solar noon. The diurnal light interception for each model was calculated from these readings. Measurements would be repeated the following day for a new series of models, thereby providing a large pool of data on the potential maximum light interception (F^g^) of a considerable number of orchard system designs. At all locations, measurements were done in midseason (January) when the leaf canopy was fiiUy developed for the season (maximum LAI) and the sun was at its highest altitude and azimuth, and also at harvest (March to May, depending on the apple variety and the location).
11
Appendix III shows a sample of readings, and illustrates the procedure followed over a one day period to obtain a series of FBS readings of light interception by "solid model" orchard systems. Prior to each set of hourly readings, the flatbed solarimeters were calibrated, and their levels checked to ensure the thermopiles were horizontally positioned.
The locations at which flatbed solarimeter measurements of light interception were made were as follows:
Stanthorpe, Qld 28°39'S 151°56'E Orange, NSW 33°19'S 149°05'E Manjimup, WA 34°15'S 116°09'E Lenswood, SA 34°57'S 138°49'E Batlow, NSW 35°32'S 148°10'E Shepparton, Vic 36°23'S 145°24'E Mornington Peninsula, Vic 38°18'S 145°irE Grove, Tas 42°59'S 147°05'E
Plate 2, Shadows cast in late afternoon in Stanthorpe, Qld by solid models orientated north-south. These models are of system 9 (Table 2), representing trees of "Christmas tree" shape, height 2.8 m, basal spread of 1.25 m into each alley, and row spacing (alley width) of 6 metres.
Note that the rows are too far apart for the designated tree height and spread, and that even late in the day the cast shadow from trees still does not encroach onto adjacent rows. The microvolt integrators used to measure the electrical output from each flatbed solarimeter are visible in the foreground.
12
(ii) Light penetration and distribution within apple trees
Light levels, yield, fruit quality and leaf area distribution were measured within apple trees of a range of varieties. The aims of this approach were to:
- determine the critical light levels required for high yields and fruit quality, and provide values for I in the light interception model on page 8 (I is the level of irradiance considered as the lower limit for well-illuminated canopy).
- compare the diurnal patterns of light distribution and the volumes of well-illuminated canopy for a range of orchard system designs.
- measure the effects of changes in tree dimensions and increases in leaf area index on the light distribution and productivity of a number of orchard systems.
- determine the tree conformations that maximise the volume of well-illuminated canopy.
(a) The measurement of light
Lightmeters were positioned at different points within the tree canopy to encompass a broad range of light intensities, from canopy regions that were almost permanently dark and shaded, through to parts of the tree that were always well-exposed to sunlight. The yield and quality (size, colour, TSS, firmness, sunburn, russet) of fruit in the vicinity of lightmeters was assessed, as well as the leaf area distribution of the tree. Lightmeters were also positioned above the tree to measure incident sunlight (Plate 3), and light levels within the canopy were calculated as a percentage of the above tree levels.
Light was measured using up to 16 PAR (photosynthetically active radiation) sensors with spectral response 400 to 700 mm (Plate 4). The sensors consisted of cosine-corrected silicon cells, and were individually calibrated. A 16 channel data logger (model LL-128, Monitor Sensors, Caboolture, Qld, Australia) with 224K memory and 4.5 watt solar panel recorded the output from each lightmeter (Plate 5).
The data logger was configured to record the readings from each of the 16 channels every six minutes, from sunrise to sunset. Each lightmeter reading was the integral of the total PAR received during the previous six minutes. Light readings above and within a tree were recorded over several consecutive days, then downloaded onto a laptop computer and later collated and analysed in the laboratory.
In the final year of the project, a ceptometer (Plate 6) was also used to measure the light interception by several orchard systems. The ceptometer (model SF-80, Decagon Devices, Washington, USA) consists of 80 PAR sensors spaced at 1 cm intervals along an 80 cm long probe, and a microprocessor that records a single average value from these sensors at each reading. Depending on the size and complexity of the orchard system design, up to 40 separate ceptometer readings were taken in series at each time of measurement, so that light penetration to the orchard floor was representatively sampled. "Above canopy" incident sunlight was also measured on each occasion, so that light interception by the trees could be calculated. Readings were also taken at different heights in the tree canopy, to look at changes in light penetration within the tree.
13
Plate 3. PAR lightmeters positioned above Gala trees to measure incident sunlight.
Plate 4. PAR lightmeters positioned within the lower canopy of Fuji (Nagafu 2) trees.
14
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Plate 5. Simon Middleton inspects a 16 channel data logger and solar panel. 3:
Plate 6. Alan McWaters uses a ceptometer to measure sunlight levels.
15
(b) Field trial sites
Fieldwork was undertaken within blocks of trees on commercial apple orchards and State Department of Agriculture Research Stations in all of the apple-producing states of Australia. The trial sites included a range of apple varieties, rootstocks, tree vigours and planting densities as summarised in Table 1. The latitudes of all trial sites are as previously indicated on page 12, extending from Stanthorpe (28° 37'S) in the north, to Huonville (43° 02'S) in the south.
All orchards were managed according to standard commercial practices, and under-tree trickle irrigation systems were generally used to water trees as required. Weed-free herbicide strips were maintained beneath the tree rows, whilst the inter-row alleyways usually consisted of a regularly mown grass sward. Pest and disease control were based on orchard monitoring and Department of Agriculture spray and IPM recommendations. Proprietary fertilisers were applied to trees as necessary.
In addition to the sites summarised in Table 1, an orchard systems trial was planted at Applethorpe Research Station, Qld in winter 1993, to compare the productivity, management and viability of intensive systems for apple production under Australian light conditions. The trial contains 1650 trees and consists of Hi Early Red Delicious, Royal Gala, Red Fuji (Nagafu 2) and Summerdel trees planted as single-row, double-row, three-row and five-row systems on several rootstocks, including MM106, M3428, Mark and M26. Each of the 16 variety x planting system combinations is replicated four times, with planting densities that range from 1090 to 3000 trees per hectare.
The trial has cropped for two seasons and is set to provide a pool of information on how closely current orchard systems approach 'the ideal', and what orchard design and tree management steps are required to improve orchard productivity. Field measurements of how yield and fiiiit quality in this trial are affected by the light interception, leaf area and dimensions of trees in each system form the partial basis of the new project AP97010 -'Increasing the yield and fruit quality of Australian apple orchards'. The South Australian data in Table 7 provide some preliminary results and trends from this type of approach.
16
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18
RESULTS
Since a considerable amount of data was generated in this project as a consequence of including so many sites, it is only practical to present a selection in this report. The results presented, however, were typical of all sites (except as otherwise indicated), and illustrate all of the significant project results. To present all results in detail would be impractical and unnecessarily complicate and confuse the information presented.
(i) Flatbed solarimeters
There is insufficient space to describe and report the results from all the models used, however several important trends emerged from the flatbed solarimeter estimates of orchard light interception.
Flatbed solarimeter measures in apple orchards in all Australian states (latitudes 28°37'S to 42°59'S) show that in mid-season (January), when the trees are at full leaf and the sun is at its highest altitude and azimuth, north/south rows always intercept more light than comparable east/west rows (Table 2). It is of particular interest that Fn,ax for ^^Y apple orchard system in January was similar at all sites throughout Australia (Table 2), and demonstrates that there is little latitudinal effect on midseason light interception at the relatively low latitudes (28°S to 43°S) in which Australian apples are produced.
The light interception of easfwest rows increases substantially in March/April (Table 3), as solar altitude and azimuth decline during autumn. This is in contrast with north/south rows, where seasonal changes in the angles of incident solar radiation have little effect on Fj^^^, with diurnal light interception relatively unchanged between January and March (Table 3).
Latitudinal effects on F^^^^ occur later in the season, when the effect of row orientation on light interception varies with latitude. At the time of Red Delicious harvest (March) in Stanthorpe, Qld, N/S rows still intercept more light than E/W rows, whereas at the higher latitude of Tasmania, E/W rows now intercept more light than the comparable N/S rows (Table 4). The autumn equinox occurs in late March, when the sun is over the equator and day and night both approximate 12 hours. The two latitudinal extremes of Australian apple production are presented in Table 4, and illustrate the effect of the seasonal tilt of the earth on potential light interception at the equinox, which also coincides with the apple harvest season.
The light interception of E/W rows is relatively constant over the course of a day, whereas the diurnal light interception of N/S rows changes significantly (Figure 1). In midseason with the sun high in the sky, the shading patterns of E/W rows are largely along the row, such that one tree shades the adjacent trees in the row for most of the day, with the exception of a brief period centred on solar noon. With N/S rows the tree shadows are cast across the alleyway, and inter-tree shading only occurs early and late in the day when the cast shadow of one hedgerow encroaches the adjacent row. Hence, midseason shading between trees of N/S rows is much less than between trees in E/W rows. It is noticeable in Figure 1, however, that in Tasmania in March, the light interception of E/W rows decreases late in the day. This is a direct consequence of low solar altitude and azimuth, and, although light interception is lower from midaftemoon onwards, the southern sides of E/W rows begin to receive exposure to fiill sunlight and are "well-illuminated". This effect declines at more northerly latitudes.
19
Orchard light interception is increased with taller trees and narrower alleyways (Tables 2-5). Increasing tree height from 2.8 to 4.3 metres increases light interception by six to 10 percent, however reducing alleywidth from 6 metres to 4 metres has a greater effect, with a 14 to 24 percent increase in light interception (Tables 2 and 3).
Regardless of latitude and row orientation, the cast shadows of trees progressively lengthen as solar altitude and azimuth decline towards equinox (late March) and then beyond towards the winter solstice (June). Thus, late in the season and at harvest, long shadows can be cast by relatively short trees, and orchard system light interception may increase substantially (Tables 3 and 5). The data for Orange, NSW (Table 3) and Manjimup, WA (Table 5) are typical of the majority of apple producing regions in Australia, with a very large increase in the light interception by E/W rows between January/February and March/May, and a much smaller increase for N/S rows over the same period.
The high light interception of an orchard system late in the season can therefore be misleading, with systems consisting of small trees and/or wide alleyways showing acceptable light interception (Table 5, compare the F^a^ of systems 1 to 4 (short trees) in February and May). It is of more relevance in comparing the productivity of orchard system designs, to measure the light interception in midseason when the sun is in a more overhead position and shining down through the canopy, rather than later in the season when incident sunlight is more from the sides of the trees and through adjacent hedgerows.
Taller trees and narrower alleyways increase the likelihood of deleterious shading of adjacent trees and rows, with cast shadows encroaching on neighbouring trees for longer periods of the day. This effect is exacerbated as the season progresses towards harvest. The orchard light interception may be higher, but the increase is due to greater row to row shading with potentially harmfril effects on light distribution within the canopy.
Multi-row systems minimise the orchard floor area that consists of tractor alleyways, and can significantly increase light interception through higher tree densities (Table 5 compare systems 4, 5 and 6). Trees must be kept short, however, or internal shading effects will negate any gains from increased light interception. At 75 to 95% light interception in February, the 3.6 metre trees in the double row and triple row systems at the high planting densities shown in Table 5 are too tall, and shading each other for much of the day.
The excessive inter-tree shading even in midseason is also evidenced by the small irxrease in light interception that occurs for these trees between February and May. The light interception of tall trees in systems 5 and 6 increases by just 6% and 1% respectively, compared with 14 and 24% increases for the corresponding short trees over this period (Table 5). At the other extreme, trees as described for system 9 (Tables 2 and 3) that are separated by 6 m wide alleyways intercept just 40% of incident sunlight, and are of insufficient canopy volume and planted too far apart to attain high productivity.
20
Table 2. The % light interception (F ^ j) in January (midseason) by 'solid' non-transmi
System Row Alley Tree Stanthorpe Orange Batlow Shepparton Mo orientation width height Qld NSW NSW Vic
1 N/S rows 6 m 2.8 m 64 63 63 64
2 N/S rows 4 m 2.8 m 83 81 82 81
3 N/S rows 4 m 4.3 m 89 87 88 86
4 N/S rows 6 m 4.3 m 73 73 72 74
5 E/W rows 6 m 2.8 m 52 47 54 49
6 E/W rows 4 m 2.8 m 72 66 73 66
7 E/W rows 4 m 4.3 m 83 73 79 76
8 E/W rows 6 m 4.3 m 61 52 62 56
9 N/S rows 6 m 2.8 m 43 41 42 40
10 N/S rows 4 m 2.8 m 58 57 59 57
Systems 1-8: Rectangular cross-section (vertical side, continuous hedgerow canopy at all height Systems 9-10: Angled cross-section (pyramidal shape, well defined central leader with 'gaps' bet
The maximum tree spread of all systems is assumed to be 1.25 m into each adjacent alleyway.
Table 3. The % light interception (F a ) in January (midseason) and March/April (harves apple orchard systems at Orange, NSW (33"19'S) and Grove, Tas (42°59'S).
System Row Alley width Tree height
Orange NSW
System Row Alley width Tree height January March orientation F„ax (%) F^ax (%)
1 N/S rows 6 m 2.8 m 63 61
2 N/S rows 4m 2.8 m 81 81
3 N/S rows 4m 4.3 m 87 86
4 N/S rows 6 m 4.3 m 73 70
5 E/W rows 6m 2.8 m 47 66
6 E/W rows 4m 2.8 m 66 88
7 E/W rows 4m 4.3 m 73 93
8 E/W rows 6 m 4.3 m 52 78
9 N/S rows 6m 2.8 m 41 40
10 N/S rows 4m 2.8 m 57 57
Systems 1-8: Rectangular cross-section (vertical side, continuous hedgerow canopy at all height Systems 9-10: Angled cross-section (pyramidal shape, well defined central leader with 'gaps' bet The tree spread of all systems is assumed to be 1.25 m into each adjacent allejrway.
Table 4. The effect of row orientation on % light interception (Fmax) in March by 'solid' non-transmitting apple trees at Stanthorpe, Qld (28*'37'S) and Grove, Tas (42°59'S)
Row orientation Tree height Alley width Stanthorpe Qld Grove Tas
N/S rows 2.8 m 6m 69 63 E/W rows 2.8 m 6m 57 66
NE/SWrows 2.8 m 6m 76 70
N/S rows 4.3 m 6m 77 76 E/W rows 4.3 m 6m 69 83
NE/SW rows 4.3 m 6m 85 85
The tree spread of all systems is assumed to be 1.25 m into each adjacent alleyway. Trees are of rectangular cross-section (Figure 8).
Plate 7. Pink Lady fruit sunburnt through exposure to radiant heat. With inadequate canopy protection the fruit is exposed to full direct sunlight during the afternoon.
23
Table 5. The effect of row orientation, tree height and planting density on % light intercep and May (Pink Lady harvest) by solid, non-transmitting trees at Manjimup, WA
SYSTEM ROW ALLEY PLANTING DENSITY SHOR ORIENTATION WIDTH (TREES HA^) 2.5 m
1.8 m be with
Short trees Tall trees February F^ax (%)
1. Single-row E/W 6 m 925 833 30
2. Single-row EAV 4m 1380 1250 41
3. Single-row N/S 6m 925 833 31
4. Single-row N/S 4m 1380 1250 45
5. Double-row N/S 4m 1860 1700 58
6. Triple-row N/S 4m 2830 2550 62
Trees are of angled cross-section and of similar design to those shown in Plate 2 (pyramidal shape between trees). Total tree spread at the base assumed to be 2.0 m for tall trees (1.0 m in all directions from the trun
Figure 1. The effect of row orientation on the diurnal light interception (Fmax) in January (mid-season) and March of a hedgerow apple orchard system at Grove, Tas (43 °S)
(Systems 4 & 8 - Table 1. Tree height 4.3m, alley width 6m.)
100
January
Eastern Summer Time
March
Eastern Sununer Time
N/S row E/W row
25
(ii) Light penetration and distribution within apple trees
Detailed measures of light distribution within apple trees of a wide range of varieties showed the huge diurnal variation in light levels that can occur at any given point in the canopy (Figures 2-6). This is what makes the measurement of light in any type of tree canopy difficult. Light measurements must be taken at very frequent intervals between sunrise and sunset to adequately sample this diurnal variability, and to subsequently allow yield and fr^lit quality to be correlated to measured sunlight (PAR) levels with a high degree of accuracy. To fiirther ensure the accuracy of PAR (photosynthetically active radiation) measures undertaken in this project, and more importantly of the conclusions made from these measures, there was considerable replication of the light recordings made, with measurements repeated over several consecutive days and at different times of the growing season. Measurements were also done at a large number of sites that included apple production regions in all states of Australia to build up a pool of information from which consistent trends emerged.
Figures 2 to 6 summarise these trends and illustrate them with a small sample of data drawn from the sites outlined in Table 1. Light levels in Figures 2 to 6 are of readings integrated over a six minute period at each hour. Integrated data was recorded every six minutes between sunrise and sunset, but for simplicity only the readings recorded on the hour are graphed. Calculations of % diurnal PAR in these figures are based on ALL lightmeter readings taken between sunrise and sunset. Based on the light measures undertaken within apple trees at all sites, the most important and consistent results are as follows:
• Even in 'well-illuminated' trees where considerable light penetrates the canopy and reaches the orchard floor, some parts of the tree receive less than 10% of incident sunlight levels throughout the day. At such low light intensities, fruit set and quality is poor. Figures 2, 3, 4 and 5 show the diurnal light levels in such unproductive parts of the canopy, with unacceptable quality fruit of poor size and colour produced where PAR levels were just 3 to 16% of above tree PAR.
• Good quality fruit of acceptable size, colour and TSS generally occurred in regions of the canopy receiving 40% or more of incident PAR. The graphs in figures 2 to 6 show good quality fruit was produced in parts of the canopy receiving between 43% and 82% of diurnal sunlight levels. Of more significance is that provided the canopy was 'well-lit' during the morning, exposure of the canopy to only low or medium light levels in the hot afternoon period was sufficient to ensure good fruit quality in those regions of the canopy (Figure 2).
• If fruit are exposed to direct sunlight (unprotected by leaf) for just one to two hours a day, this can be sufficient to induce sunburn through radiant heat (Plate 7, page 23). Other fruitlets may receive considerably more sunlight during an entire day and suffer no sunburn. Fruit most prone to sunburn are those that can be relatively shaded for much of the morning, then receive full exposure to direct light during the early afternoon period (Figure 5).
26
• Cloud cover has a dramatic effect on incident light levels (Figures 3 and 4), and can also alter the pattern of light penetration through the tree canopy as the component of diffuse (scattered) light significantly increases. With the onset of heavy storm cloud and rain, incident light levels at Orange, NSW plummeted by 88% from 1600 to 200 milHMoles m" in the space of an hour (Figure 4). This rapid decline in light levels occurs during afternoon storms that are common in many of Australia's apple producing regions during the growing season, and unacceptably low light levels occur in all parts of the tree during such dull, wet conditions.
An overcast January day at Shepparton, Vic also showed the very low light levels that can occur under cloud cover (Figure 3). The morning was dull and wet with measured PAR continuously less that 100 milliMoles m' above and within the tree canopy. As the cloud cover dispersed or thickened the light levels fluctuated accordingly, but never exceeded 600 milliMoles m'^ all day. This is less than 40% of the light levels to be expected on fine, clear days at this latitude in January and contrasts with the 1500+ milliMoles m" recorded near solar noon on fine days at Batlow, NSW (Figure 2) and on the Momington Peninsula, Vic (Figure 5).
• In addition to their lower midseason (January) light interception, a fiirther deficiency of east/west rows is their poor light distribution, as illustrated in Figure 6. The sunlight intercepted by east/west rows is largely on the exposed northern side, with the southern side remaining relatively shaded. The lower southern sides of east/west rows receive as little as 10% of diurnal PAR levels, and can subsequently have low fruit set and produce poor quality fruit. In contrast, canopy regions on the northern sides of the rows that are protected by some leaf canopy can receive optimal light and produce excellent quality fruit, whilst other positions on the northern side that are exposed to full sunlight in the afternoon and are shaded in the morning will produce svmbumt fruit.
In Figure 5, the canopy regions receiving 46 and 61% of diurnal PAR levels produced good and excellent quality finit respectively. This, however, was in Tasmania, and under the hotter and drier summer conditions of the more northerly latitudes of Victoria and New South Wales, such fruit will be prone to sunburn. The light levels shown in Figure 6 were measured within a well-structured Fuji tree with vigour under control, yet much of the lower and southern side of the tree canopy still received less than 10%) of incident light levels. The poor, uneven light distribution illustrated in Figure 6 is dependent on tree vigour, and would be even further exacerbated with taller trees, narrower alleyways and denser leaf canopies.
27
Figure 2. Light levels (PAR) within a Hi Early Delicious tree (N/S row, 6 x
CM
To CD
CC
Batlow, NSW (35^ 32'S ) - January - F Note: Good quality fruit only needed exposure to low to med
: The symmetrical curve of incident light levels under c
2000
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00
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Fruit Quality % Diurnal PAR
^ PAR Above Hail Net ^ Poor 100% 3%
Med 26%
Figure 3. Light levels (PAR) within a Hi Early Delicious tree (EAV row, 6
Shepparton VIC ( 36<» 23'S ) - January - AM Ra
Note: Effect of cloud in the early afternoon on : Poor quality fruit exposed to low light
600
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Good 62%
Figure 4. Light levels (PAR) within a Hi Early Delicious tree (N/S row
CM
o
1800
Orange, NSW ( 33^ 19'S ) - February - AM F
Note: Dramatic drop in light levels with onset of heavy cloud : Low light levels in all parts of the tree in dull, wet con
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Good ^ G o 82% 45%
Figure 5. Light levels (PAR) within a Hi Early Delicious tree (Vase, 6.
Hastings, VIC ( 38° 18'S ) - January - F
Note: Variation in light levels that can occur at a given point : Sunburnt fruit was exposed to Ml sun in the PM.
CM
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Figure 6. Light levels (PAR) within a Fuji tree (EAV row, tree spaci
Grove, TAS (43°S) - January - Fine,
800
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Although orchard light interception is increased with taller trees and narrower alleyways, a point will be reached where light distribution in the canopy, and hence yield and apple quality, are adversely affected. Apart from the tree 'form' effects of tree height, shape, row orientation, alleywidth, and planting density/arrangement already mentioned, light distribution within the canopy is also influenced by leaf area index (leaf density and distribution).
Table 6 shows for two apple orchard systems, the large effect that leaf area index (LAI) can have on orchard light interception. More importantly, Table 6 shows that as LAI increases, the effect on total orchard light interception reduces. For example, doubling the LAI of the 2.5 m high trees from 1.0 to 2.0 increases light interception by 14%, yet a further increase in LAI from 2.0 to 3.0 yields only a 5% gain in light interception. Given the previous gain of 14%, the relatively small 5% increase in light interception is in part at the expense of good light penetration to lower parts of the tree, and reduces the volume of "well-illimiinated" canopy. An LAI of 2.0 to 2.2 would therefore optimise light interception and penetration, and maximise the productivity of this orchard system design.
The light interception and productivity of four orchard systems at Lenswood, SA in the 1996/97 season (Table 7) illustrates several important results from this project, and is typical of results obtained from other sites.
Vigorous 5.5 metre high trees (Plate 10) on MM 106 rootstock intercepted only 2% more light than MMl 11 trees that were almost 2 metres shorter (Table 7, compare Systems 1 and 2). The effect of the additional 1.9 metres of free height was merely to double the LAI from 1.65 to 3.34, and reduce the volimie of "well-illuminated" canopy through internal shading effects. Although yields of 47 tha" were produced, poor light distribution due to excessive tree vigour meant that only 30 tha' was of acceptable quality.
With an LAI of 0.88 the Red Fuji trees on M26 (Table 7, System 3) are of insufficient vigour for high orchard productivity. Although intercepting 47% of incident PAR in April, the Fuji/M26 trees are spaced too far apart for the vigour of the rootstock, and large 'gaps' occur between adjacent trees. Light interception and productivity of this system would be improved with closer tree spacing and higher LAI. This principle is also illustrated in Table 6, where an LAI of 1.0 is too low to provide the light interception necessary for high orchard productivity.
The Pink Lady/M26 trees (Table 7, System 4) are close to the "ideal" tree conformation. In their fourth leaf in 1996/97 these frees yielded 37 tha"', with 95% of the canopy volume "well-illuminated". At a 2.8 metre tree height and with angled sides and a well-defined central leader (the classic 'Christmas free' shape), this tree conformation (Plates 8 and 9) or similar was consistently found to be the most productive at a range of sites. The LAI of 1.50 for the Pink Lady frees in Table 7 is still low, and orchard productivity will further improve with tree age, as LAI increases to 2.0 and as light interception correspondingly increases to 55 to 60%.
33
The superior light distribution of N/S rows over E/W rows is again evidenced in Table 7. With an LAI of 1.50, 95% of the canopy of N/S rows of Pink Lady/M26 trees is well-illuminated. Despite a much lower LAI of 0.88, 16% of the canopy of the E/W Fuji/M26 trees is still poorly illuminated, due mainly to shading effects on the southern sides of these rows. It should also be noted that the midseason light interception of the three E/W row systems will be lower than as shown in Table 7, due to higher solar altitude and azimuth in January.
Plate 8. An 'ideal' tree. Height of 2.8 m, triangular cross-section (Christmas tree shape) with well-defined central leader. Good light distribution is evidenced by Fuji fruit of excellent colour throughout the tree. Several PAR lightmeters are also visible.
34
Table 6. The effect of leaf area index (LAI) on the light interception of two apple orchard systems.
(Single-row hedgerows, 4 metre alleys with tree spread of 1 m into each alleyway)
Tree height F * max
LAI Light interception
1.0 38% 2.5 m .60 2.0 52%
angled sides 3,0 57% (Figure 9-bottom)
1.0 42% 4.0 m .80 2.0 62%
rectangular sides 3.0 71% (Figure 9-top)
Plate 9. An ideal tree height, shape and leaf area distribution.
35
Plate 10. It's a pity that the ' ideal' 2.8 m high tree configuration in Plate 9 is atop an overvigorous 5.5 m tall Braeburn/MM106 tree! This tree is of similar appearance and structure to the Red Fuji/MM106 tree described in Table 7. Lenswood, South Australia.
36
Table 7. The light interception, tree vigour and productivity of four apple orchard syste
Variety/Rootstock Row orientation
Planted % Light interception
Tree height (m) LAI
1. RedFuji/MM106 EAV 1990 70 5.5 3.34
2. RedFuji/MMlll E/W 1990 68 3.6 1.65
3. RedFuji/M26 E/W 1990 47 3.0 0.88
4. PinkLady/M26 N/S 1993 49 2.8 1.50
- Tree spacing of all four systems is 4 m x 2 m (1250 trees ha* ). - Light interception was measured with a ceptometer (Plate 6) in April 1997. - The volume of "well-illuminated" canopy is the % canopy volume where >80% of fruit were of
DISCUSSION
Sunlight provides the energy for a tree to produce fruit, and the interception of light by the leaf canopy is necessary for photosynthesis. It is the exposure of leaves to sunlight that 'drives' the normal physiological processes in the apple tree necessary for tree growth, fruit bud differentiation, cropping and the development of fruit size, colour and quality.
Measurements of light in this project were always of phytosynthetically active radiation (PAR), which is short-wave solar radiation of 400 to 700 nm wavelengths, and sometimes referred to as visible light. It is PAR that specifically provides the light energy for phytosynthesis (Monteith, 1969). Photosynthetically active radiation is very strongly absorbed by apple leaves, hence there is rapid attenuation of PAR within an apple tree and light levels in many parts of the canopy fall to well below 10% of incident levels (Figures 2-6).
Although incident light levels in Australia are relatively high during the growing season (October to April), cloud cover and the apple tree canopy itself can rapidly deplete PAR to levels that severely impact on potential orchard productivity, most especially when trees are excessively vigorous. For the early part of the growing season the spur leaves in close proximity to a particular fruit are its major source of assimilate (Ferree and Palmer, 1982), and it is essential that spur leaves receive good exposure to light. After midseason, spur leaf photosynthesis insufficient to maintain fruit growth, and shoot leaves become an important source of assimilate supply (Ferree and Palmer, 1982; Barritt et al., 1987).
Parts of the canopy receiving inadequate sunlight are therefore either totally unproductive, give low yields or produce fruit of poor quality. The most common effects of shading are reduced fruit size, colour and soluble solids content, and reductions in tree growth, root growth, fruit bud formation and fruit set (Middleton, 1990). Yield reductions from shade are largely due to small fruit size, fruit abscission and poor fruit set (Doud and Ferree 1980).
With higher light interception during the season, north/south row orientation should always be favoured over east/west rows. Light interception by east/west rows increases towards the end of the season, and at harvest (late March/April) is greater than north/south orientations, but this is too late to benefit fruit bud initiation, seasonal photosynthesis and fruitlet development. The light distribution within east/west rows can be poor and is dependent on tree vigour. The sunlight that is intercepted by east/west rows is largely on the exposed northern side, with the southern side remaining relatively shaded. If trees are too tall, alleyways too narrow or the leaf canopy too dense, the deficiencies of east/west rows become more marked. Here, fruit on the upper northern side of the trees is susceptible to sunburn, while low yields of poor size and quality are produced on the southern side.
Maintaining a narrow canopy depth in all the directions from which sunlight may be incident is a sound principle that is a feature of many apple orchard designs. Hence, in productive orchards all fruit-bearing regions are never far from an outside surface of the tree. If the leaf canopy is too dense, a depth of less than 30 centimetres can make regions below or behind this unproductive.
38
Trees of angled cross-section and with a well-defined central leader confined within the row, improve light penetration to lower parts of the canopy (Figure 7). This is the classic 'Christmas tree' shape, characterised by a narrow canopy depth at all points. Trees of rectangular cross-section can intercept more light (Tables 2 and 3), however if the canopy is too dense this will be at the expense of light penetration, yield and fruit quality lower in the tree.
Apple yields have been linearly related to light interception (Jackson 1978), however lowered productivity can occur at very high levels of light interception through poor light distribution in the tree. A tree height to clear alley width ratio of 1:1 (Table 2, systems 1, 5, 9), intercepts insufficient light for high productivity (Table 2, systems 1, 5, 9), with trees too short (Figure 8) and/or rows too far apart (Figure 9).
Increasing the tree height to clear alley width ratio from 2:1 to 3:1 (Figure 8) for single-row hedgerow trees increases potential light interception by only 6 to 7% (Table 2, compare system 2 with system 3). Although this can lead to small yield improvements, any gain is usually at the expense of yield and fruit quality low in the canopy. With insufficient light, the crop closer to the ground declines and is of poor quality. It is not economically desirable to concentrate the cropping zone towards the top of tall trees, and increasing tree height beyond 2.8 m is an inefficient way to increase light interception and orchard productivity (Table 7).
The ratio of tree height to clear alley width is a simplistic concept that can be complicated by factors such as tree shape. For example, in Figure 9 it is obvious that for angular cross-section trees, rows are too far apart and/or trees are too short when the ratio of height to alley width is 1:1 (system 9). At a tree height: clear alley width ratio of 2:1, however, rows will be too close together if trees are of rectangular cross-section (Figure 9, System 2), whereas the row spacing will be close to optimal if trees are of triangular cross-section (Figure 9, System 10).
It should also be noted from Figure 9 that System 2 will have high light interception and low light penetration, whilst System 10 will have lower light interception and higher light penetration. This demonstrates the dilemma in apple orchard system design, where an improvement in light interception will often mean a sacrifice in light penetration, and vice versa. Hence optimal orchard design will always involve a trade off between light interception and light penetration.
A good guide to apple orchard productivity is to look at the shadows cast by trees during mid-morning or mid-afternoon on a fine, clear day in December or January. 'Speckling' of light on the orchard floor - small patches of light at regular intervals in the main block of cast shadow (Plate 11) - suggests that trees are well-structured, that light is reaching all regions of the canopy, and that yields and fruit quality are high and close to optimum.
If there are numerous patches of light that take up more of the ground area that the shadow, it is likely that tree growth and vigour are too low for high productivity. If the shadow is a solid block with no light reaching the ground, then the trees are too vigorous, with a dense leaf canopy and poor light distribution reducing yield and fruit quality. If the shadow encroaches well into the adjacent row of trees then the trees are too tall or wide for the designated alley space.
39
Over 70% of the Australian apple crop is produced within 5" of latitude (SS IQ-S to 38°18'S), although in midseason (January) latitude has relatively little effect on F„ax, and it is tree 'form' effects, planting density and LAI that have greatest influence on orchard light interception. The South Australian results (Table 7) provide a good 'snapshot' that compares the productivity of several orchard systems on the basis of light interception, tree size and LAI, and this approach has been expanded in current trialwork.
Leaf area index (LAI) represents orchard LAI, and is defined as the ratio between the total leaf surface area (m^) and the total ground area (m^) assigned to the trees (Sansavini et al., 1985). The LAIs of 0.88 to 3.34 in Table 7 embrace the normal range of apple orchard system LAIs. Values below 2.6 are typical for hedgerow apple orchards. An extreme value of 4.6 was cited by Jackson (1980a) for very large trees with canopies that overlapped in all directions, and therefore practically formed a continuous canopy.
Alleyways are an essential yet inefficient feature of orchards, representing areas of land that are non-fruiting and non-productive. Despite this, the contribution of alleyways in providing 'gaps' for light penetration in the orchard is important. Alleyways of 6 metres are too wide for high orchard productivity, especially when trees are grown on dwarf and semi-dwarf rootstocks. For example, with a maximum possible light interception (Fmax) of just 40%, trees of system 9 (Table 2) are too far apart to ever produce adequate crops. In minimising alley width, trees must also be kept corresponding short so as to reduce shading from adjacent rows.
Substantial yield and fruit quality gains are best achieved by maximising the orchard surface area covered by the external fmiX producing canopies of trees, rather than by increasing tree height. High density plantings of short trees have a larger ex than temal surface area exposed to light, and a lower volume of "poorly illuminated" canopy, lower-density plantings of tall trees. Multi-row systems reduce the orchard area 'wasted' by tractor alleyways, but at their high planting densities (typically over 2000 trees per hectare) must utilise relatively small trees to ensure all regions of the canopy receive adequate light. Precocious dwarfing rootstocks such as M9 and M26 produce trees of an appropriate size, and yield heavy crops within three to four years of planting.
Experience with multi-row systems for apple in Australia is limited, although research trials in Queensland, New South Wales and South Australia are currently evaluating the performance of dwarfing rootstocks in high density plantings (James et al., 1996). Results to date show that trees on some dwarfing rootstocks have insufficient canopy volume to support high yields, and imder Australian sunlight intensities may produce fi-uit susceptible to sunburn through exposure to radiant heat, vmless protected by hail netting. The establishment costs of multi-row systems are high, and the economic viability of these systems relies on harvesting significant crops within three years of planting.
Shading and vigour control problems frequently occur in the standard single-row hedgerow orchards. Trees are often planted on semi-vigorous rootstocks, encouraged to grow as quickly as possible to fill their allotted spaces, then after three to four years expected to switch to fruiting mode. Most problems occur when free spacing is too close for the vigour of the rootstock used under the local soil, climatic and management conditions; or conversely, the rootstock is too vigorous for the planting density used. Incorrect decisions
40
made at planting in the selection of rootstocks and tree density are the source of many of the yield and fruit quality problems evident in Australian apple orchards, take many years to overcome, and are expensive in terms of both lowered productivity and increased tree management costs. Options to control vigour in such cases include summer pruning, chunk dormant pruning, trunk cincturing, root pruning, NAA paints and regulated deficit irrigation (RDI).
Plate 11: 'Speckling' of light on the orchard floor - the small patches of light at regular intervals in the main block of cast shadow suggest good light penetration to all parts of the canopy,
The cast shadow outline of each tree is visible and shows the light interception due to tree 'form' (height, shape, spread, planting density). As these 5 yo trees age and grow bigger the
cast shadow area will increase, as will % light interception.
41
Figure 7. £llect of canopy shape on light penetration *
Additional canopy depth in a rectangular shape hedgerow through which light must penetrate to reach a given point in the tree.
Figure 8. Changes in tree height to clear alley width ratio with increasing tree height
3:1
1:1
2:1
Systems 1 & 5 (Table 2)
Trees too short
Systems 2 & 6 (Table 2)
Close to optimum
Systems 3 & 7 (Table 2)
Trees too tall
42
Figure 9. Changes in tree height to clear alley width ratio with n
1:1
System 1 ROWS too far apart
System 9 Rows too far apart
Rows t
S Clos
CONCLUSIONS AND RECOMMENDATIONS
• Orchard productivity is a term that consists of a yield component and a fruit quality component. The reason why one orchard system is more productive than another can be related to the interception and distribution of light in the tree canopy.
• The two objectives in apple orchard system design are to:
- maximise light interception -^ high yields - optimise light distribution -^ high fruit quality
• Orchard light interception is increased with taller trees and narrower alleyways, but a point will be reached where light distribution in the canopy, and hence yield and apple quality, are adversely affected. As orchard LAI increases there will be a trade off between light interception and light penetration.
• Even in 'well-illuminated' trees where considerable light penetrates the canopy and reaches the orchard floor, some parts of the tree can receive less than 10% of incident sunlight levels throughout the day. At such low light intensities, fruit set and quality is poor and trees require restructuring to open up the canopy in those regions.
• Maintaining a narrow canopy depth in all the directions from which sunlight may be coming is a sound principle that is a feature of many apple orchard designs. The more leaves there are above or outside a certain point in the canopy, the less likely it is for light to reach there. In productive orchards all fruit-bearing regions are never far from an outside surface of the tree.
• Trees of angled cross-section, and with a well-defined central leader confined within the row, improve light penetration to lower parts of the canopy. This is the classic 'Christmas tree' shape, characterised by a narrow canopy depth at all points. Trees of rectangular cross-section can intercept more light, however if the canopy is too dense this will be at the expense of light penetration, yield and fruit quality lower in the tree.
• North/south row orientation should be favoured over east/west rows. North/south rows intercept more sunlight during summer, and have superior patterns of light distribution.
• An orchard LAI of 2.0 and a 2:1 ratio of tree height to clear alley width are good guides to high orchard productivity.
• 'Well-illuminated' canopy for high yields and good fruit quality needs to receive at least 40% of incident duimal light levels. This light should preferably be received evenly throughout the day, or concentrated during the morning. Fruit that is shaded in the morning then exposed to full direct sunlight in the early afternoon is especially prone to sunburn.
44
•
Observation of the shadows cast by trees during mid-morning or mid-afternoon on fine midsummer days is a simple way to visually assess the light interception, light distribution and productivity of apple trees in the field. ' Speckling' of light in the main block of cast shadow (Plate 11) suggests that trees are well-structured and sunlight is penetrating to all regions of the canopy.
Poor yields and fruit quality are always associated with either inadequate tree vigour and canopy volume, or excessive tree vigour and resultant shading effects.
The light interception and productivity of trees with an orchard LAI of less than 1.0 is always too low. At the other end of the scale, orchard productivity can be expected to decline as orchard LAI increases above 2.5.
A tree height of approximately 2.8 metres and midseason light interception of 60% are two key objectives in apple orchard system design for high productivity under Australian light conditions.
A current project is measuring the light interception, leaf area, canopy dimensions, yield and fruit quality of a wide range of existing orchard systems throughout Australia, both on research stations and in commercial orchards and 'best practice' blocks. This project will identify how closely Australian apple orchards are approaching their potential productivity (based on factors such as an 'ideal' 60% light interception in midsummer and a tree height of 2.8 metres), and what tree management/orchard design steps are required for our orchards to more closely achieve this.
Sunlight is free, and it is essential to take full advantage of this resource that is so readily available to us all.
45
PUBLICATIONS
Middleton, S.G. and McWaters, A.D. (1997). Apple orchard design, tree management and hail netting. Apple Industry Information Day. QFVG. Stanthorpe, Qld. 14 August 1997.
Middleton, S.G. (1997). Quality orchard design and light management. ANFIC '97 Conference Proceedings. Penrith, NSW. 30 April - 2 May 1997. pp. 93-97.
Middleton, S.G. (1997). Orchard design affects productivity. Good Fruit and Vegetables Vol. 7 No. 9, p. 22. February 1997.
Middleton, S.G. (1996). Theoretical/Practical design of orchards. Proceedings 4th National Lychee Seminar. Yeppoon, Qld. 26-28 September 1996. pp. 24-29.
James, P., Middleton, S. and Campbell, J. (1996). High density planting systems for apples in Australia. In Program and Abstracts. 6th International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems. Wenatchee, Washington, USA and Penticton, British Columbia, Canada. ISHS. 17-25 July 1996. p. 41.
Middleton, S.G. (1996). Let your trees do the talking. Pome Fruits Bulletin No. 4. Tasmanian Dept of Primary Industry and Fisheries. July 1996. pp. 52-53.
Middleton, S.G. (1996). Apple orchard system design determines productivity. Pome Fruits Bulletin No. 4. Tasmanian Dept of Primary Industry and Fisheries. July 1996. pp. 69-71.
Middleton, S.G. (1995). Apple orchard system design determines productivity. Horticulture Highlights No. 4. December 1995. pp. 16-17.
Middleton, S.G. (1995). Apple orchard system design determined productivity. Pome Fruit Australia. July 1995. p. 4.
Middleton, S.G. (1995). Let your trees do the talking. Horticulture Highlights No. 2. June 1995. pp. 7-8.
Jordan, A., Mc Waters, A.D. and Middleton, S.G. (1995). An interview with Marcei Veens. Horticulture Highlights No. 2. June 1995. pp. 14-17.
46
REFERENCES
AAPGA. (1996). Comparing apples with apples. Benchmarking the Australian Apple Industry. 56 pp.
Barritt, B.H., Rom, C.R., Guelich, K.R., Drake, S.R. and Dilley, M.A. (1987). Canopy position and light effects on spur, leaf, and fruit characteristics of 'Delicious' apple. HortScience 22:402-405.
Doud, D.S. and Ferree, D.C. (1980). Influence of altered light levels on growth and fruiting of mature 'Delicious' apple trees. Journal of the American Society for Horticultural Science 105:325-328.
Ferree, D.C. and Palmer, J.W. (1982). Effect of spur defoliation and ringing during bloom on fruiting, fruit mineral level, and net photosynthesis of 'Golden Delicious' apple. Journal of the American Society for Horticultural Science 107:1182-1186.
Jackson, J.E. (1978). Utilization of light resources by high density planting systems. Acta Horticulturae 65:61-70.
Jackson, J.E. (1980a). Light interception and utilization by orchard systems, p 208-267. In J. Janick (ed.). Horticultural Reviews Volume 2. AVI Publishing, Westport, Connecticut, U.S.A.
Jackson, J.E. (1980b). Theory of light interception and a modelling approach to optimizing orchard design. Acta Horticulturae 114:69-79.
Jackson, J.E. and Middleton, S.G. (1987). Progettazione del frutteto per la massima produzione di qualita. [Modelling of orchards for maximum productivity and fruit quality.] Rivista di Frutticoltura e di ortofloricoltura 49(5):27-33.
Jackson, J.E. and Palmer, J.W. (1972). Interception of light by model hedgerow orchards in relation to latitude, time of year and hedgerow configuration and orientation. Journal of Applied Ecology 9:341-358.
Jackson, J.E. and Palmer, J.W. (1979). A simple model of light transmission and interception by discontinuous canopies. Annals of Botany 44:381-383.
Jackson, J.E., White, G.C. and Duncan, C. (1986). Economic appraisal of orchards of Cox's Orange Pippin apple on M.9 and MM.106 rootstocks. Acta Horticulturae 160:383-390.
James, P., Middleton, S.G. and Campbell, J.E. (1996). High density planting systems for apples in Australia, p 41. In Abstracts. 6th International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems. Wenatchee, Washington, USA and Penticton, British Columbia, Canada. ISHS. 17-25 July 1996.
47
Middleton, S.G. (1990). Apple orchard light interception and productivity. PhD. Thesis. University of London, London, U.K. 201 pp.
Middleton, S.G. and Jackson, J.E. (1989). 'SoHd model' estimation of light interception by apple orchard systems. Acta Horticulturae 240:83-86.
Monteith, J.L. (1969). Light interception and radiative exchange in crop stands, p.89-111. In J.D. Eastin, F.A. Haskins, C.Y. Sullivan, C.H.M. Van Bavel (eds.). Physiological aspects of crop yield. American Society of Agronomy and Crop Science Society of America, Madison, Wisconsin, U.S.A.
Morgan, D.C., Stanley, C.J., Volz, R. and Warrington, I.J. (1984). Summer pruning of 'Gala' apple: the relationships between pruning time, radiation penetration, and fruit quality. Journal of the American Society for Horticultural Science 109:637-642.
Palmer, J.W. (1977). Diurnal light interception and a computer model of light interception by hedgerow apple orchards. Journal of Applied Ecology 14:601-614.
Parry, M.S. (1981). A comparison of hedgerow and bush tree orchard systems at different within-row spacings with four apple cultivars. Journal of Horticultural Science 56:219-235.
Sansavini, S., CoreUi, L. and Giunchi, L. (1985). Peach yield efficiency as related to tree shape. Acta Horticulturae 173:139-158.
48
APPENDIX I. FRUIT COLOUR CLASSES
Rating classes used to visually access the colour of apples of red varieties. The colour variation between the Gala apples in this photo can occur within a single tree as a result of variations in light levels within the canopy.
49
APPENDIX II. SAMPLE PRINTOUT OF HOURLY LIGHTMETER READINGS FROM A DATA LOGGER
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50
APPENDIX III. SAMPLE DIURNAL FLATBED SOLARIMETER READINGS FOR 'SOLID MODEL' DESIGNS
i : : 1 • : . •
FLAT BED SOLARIMETERS - 6 MARCH 1997 - GROVE, TAS - EASTERN SUMMER TIME
CALIBRATED DATA AM : Alternating sunshine and cloud j iPM: Fine, clear, 100% blue sliy
sun & i sun & sun & j fine fine fine fine fine j fine '•, i cloud cloud : cloud clear clear clear clear clear clear | i
9:00 AM 10:00 AM 11:00 AM NOON j 1:00 PM i 2:00 PM 3:00 PM i 4:00 PM 5:00 PM \
1 1 8:45 9:45 10:45 11:45 1 12:45 1:45 2:45 3:45 4:45 i
N/S Triple Row (Standard) 8.5 39.1 119.3 206.7 245.3 230.8 182.7 120.0 1.3
- 55.0 158.0 581.0 764.0 723.0 730.0 673.0 568.0 415.0 N/S Triple Row (Tall) 2.5 7.1 21.3 70.9 59.7 14.6 0.8 0.8 0.7
8:51 9:51 10:51 11:51 12:51 1:51 2:51 3:51 4:51
N/S Double Row (Standard) 23.0 45.4 196.9 259.0 257.9 255.4 180.4 123.6 1.3
- 227.0 168.0 675.0 779.0 725.0 728.0 666.0 580.0 404.0 N/S Double Row (Tall) 12.6 37.3 167.0 258.4 249.81 214.1 136.1 73.3 20.6
j i 8:57 1 9:57 j t0:57 11:57 12:57 1:57 2:57 ; 3:57 4:57
N/S Cones x 4 rows (Standard) 54.4 84.5! 335.4 418.1 389.7 376.0 424.1 199.5 1.3
- 275.0 307.0 761.0 844.0 731.0 726.0 780.0 551.0 378.0 N/S Cones x 4 rows (Tall) 33.7 45.2 260.7 451.0 370.7 341.4 328.8 142.6 59.5
9:00 10:00 11:00 12:00 1:00 2:00 3:00 4:00 5:00
N/S Cones x 3 rows (Standard) 157.2 214.4 449.9 591.2 495.1 488.5 388.9 301.1 1.3
- 362.0 422.0 729.0 901.0 732.0 725.0 646.0 542.0 375.0 N/S Cones x 3 rows (Tall) 105.2 150.7 401.7 631.8 460.3 461.5 369.8 271.2 120.5
9:05 10:05 11:05 12:05 1:05 2:05 3:05 4:05 5:05
N/S Wood X 3 (Short) 44.7 137.4 232.7 441.3 442.4 372.5 230.8 75.9 1.3
- 150.0 351.0 559.0 793.0 731.0 722.0 640.0 527.0 361.0 N/S Wood X 3 (Tall) 30.3 69.0 159.9 386.8 361.3 258.7 64.8 24.9 4.4
9:08 10:08 11:08 12:08 !:08 2:08 3:08 4:08 5:08
N/S Wood X 4 (Short) 20.6 53.0 75.2 292.7 312.9 192.1 37.5 1.2 1.3
- 304.0 299.0 387.0 745.0 733.0 721.0 635.0 520.0 350.0 N/S Wood X 4 (Tall) 0.8 22.2 36.2 190.9 202.7 23.5 0.8 2.3 0.7
9:12 10:12 11:12 12:12 1:12 2:12 3:12 4:12 5:12 5:50
E/W Wood X 4 (Short) 1.2 20.2 40.6 39.5 49.3 66.8 98.4 96.7 120.7 12.7
- 311.0 371.0 262.0 762.0 734.0 716.0 627.0 509.0 339.0 233.0 EAVWoodx4(Tall) 0.8 14.3 15.8 0.8 0.8 0.8 0.8 50.7 91.9 11.8
9:15 10:15 11:15 12:15 1:15 2:15 3:15 4:15 5:15 5:45
E/W Wood x 3 (Short) 52.0 68.1 80.0 217.2 254.4 264.7 256.5 209.3 190.6 83.9
- 317.0 326.0 272.0 710.0 733.0 712.0 621.0 505.0 328.0 251.0 E/W Wood X 3 (Tall) 10.1 25.4 34.7 32.5 33.0 76.2 163.2 202.6 153.6 70.5
9:17 10:17 11:17 12:17 1:17 2:17 3:17 4:17 5:17
N/S Lincoln x 3 (Short) 58.0 227.0 346.1 376.3 484.8 425.2 242.5 89.4 1.3
- 338.0 592.0 602.0 586.0 736.0 720.0 614.0 494.0 321.0 N/S Lincoln x 3 (Tall) 24.4 155.5 271.0 355.1 376.2 306.6 125.5 42.9 0.7
9:20 10:20 11:20 12:20 1:20 2:20 3:20 4:20 5:20
N/S Lincoln x 4 (Short) 50.8 105.9 237.5 350.7 367.9 275.3 78.5 7.3 1.3
- 384.0 693.0 604.0 719.0 742.0 704.0 612.0 487.0 312.0 N/S Lincoln x 4 (Tall) 21.9 73.0 125.2 305.1 263.1 110.3 1.6 27.3 0.7
9:23 10:23 11:23 12:23 1:23 2:23 3:23 4:23 5:23
E/W Lincoln x 4 (Short) 68.9 74.4 59.7 117.3 177.6 202.7 222.6 9.8 111.8
- 473.0 511.0 372.0 648.0 766.0 702.0 687.0 477.0 299.0 E/W Lincoln x 4 (Tall) 41.2 65.8 31.5 7.5 0.8 0.8 99.2 170.7 80.1
9:26 10:26 11:26 12:26 1:26 2:26 3:26 4:26 5:26
E/W Lincoln x 3 (Short) 142.6 174.0 250.6 297.3 339.2 357.3 308.1 254.6 172.8
- 419.0 512.0 671.0 696.0 736.0 700.0 599.0 469.0 292.0 E/W Lincoln x 3 (Tall) 76.6 107.9 110.3 138.4 157.1 196.3 250.1 263.4 127.1
FBS measures were done as follows : 6-Mar-97 lpm,2pm,3pm,4pm,5pm (due to rain disrupting measures) 9-Mar-97 9am,10ara,l lam.noon
Refer to light readings for when cloudy, overcast conditions occurted during the FBS runs
51
I • •
FLAT BED SOLARIMETERS - 15 FEBRUARY 1997 - MANJIMUP, W.A. - VVA STANDARD TIME
CALIBRATED DATA
Fine, clear, 100% blue sky ALL day. jNB. Sun was DIRECTLY OVERHEAD at l:00pm
fine fine fine ] fine fine fine fine , fine fine
9:00 AM 10:00 AM 11:00 AM NOON 1 1:00 PM | 2:00 PM 3:00 PM 1 4:00 PM 5:00 PM ! i
8:45 9:45 10:45 11:45 12:45 1:45 2:45 1 3:45 4:45
N/S Cones Triple Row (Short) 155.1 301.1 444.6 629.5 653.6 533.8 389.9 267.2 55.4
- 633.0 879.0 1058.0 1195.0 1200.0 1131.0 980.0 739.0 466.0
N/S Cones x 3 rows (Standard) 302.6 499.6 677.8 799.6 807.9 780.9 592.4 385.1 139.7
8:49 9:49 10:49 11:49 12:49 1:49 2:49 3:49 4:49
N/S Cones Double Row (Short) 193.1 343.0 517.2 675.3 691.5 626.5 439.2 299.7 15.1
- 644.0 819.0 1066.0 1187.0 1202.0 1121.0 956.0 727.0 449.0
N/S Cones x 4 rows (Standard) 169.7 310.6 507.3 600.4 617.1 563.2 413.0 213.6 13.4
8:54 9:54 10:54 11:54 12:54 1:54 2:54 3:54 4:54
N/S Cones x 4 rows (Short) 250.8 479.6 633.7 784.2 794.1 703.3 517.8 292.0 38.6
- 658.0 938.0 1084.0 1199.0 1195.0 1116.0 943.0 698.0 432.0
E/W Cones x 4 rows (Standard) 272.9 419.4 502.9 607.7 594.0 516.8 393.5 254.4 111.4
8:57 9:57 10:57 11:57 12:57 1:57 2:57 3:57 4:57 5:49
N/S Cones x 3 rows (Short) 410.4 634.9 772.8 919.9 923.5 832.7 645.7 401.6 130.8 1.7
- 730.0 955.0 1090.0 1192.0 1188.0 1104.0 939.0 683.0 418.0 192.0
E/W Cones x 3 rows (Standard) 434.1 598.4 689.4 789.4 773.2 675.0 554.8 362.6 255.5 86.2
9:02 10:02 11:02 12:02 1:02 2:02 3:02 4:02 5:02
E/W Cones x 3 rows (Short) 389.1 723.3 757.7 893.0 906.2 834.3 639.5 454.2 226.5
- 554.0 993.0 1101.0 1194.0 1191.0 1100.0 922.0 676.0 399.0
E/W Cones x 3 rows (Tall) 343.6 638.4 676.4 801.1 797.8 696.8 507.5 338.7 225.8
9:06 10:06 11:06 12:06 1:06 2:06 3:06 4:06 5:06
E/W Cones x 4 rows (Short) 413.5 563.5 635.2 774.7 757.8 676.1 517.8 352.2 194.6
- 717.0 942.0 1109.0 1204.0 1183.0 1085.0 920,0 663.0 383.0 E/W Cones x 4 rows (Tall) 685.8 456.6 524.6 626.6 601.2 513.9 337.9 210.8 142.6
9:11 10:11 11:11 12:11 1:11 2:11 3:11 4:11 5:11
N/S Wood X 3 (Short) 124.6 339.9 503.6 738.4 734.1 545.0 292.8 57.2 1.7
- 661.0 954.0 1126.0 1199.0 1174.0 1067.0 865.0 626.0 338.0 N/S Wood X 3 (Tall) 4.2 117.4 352.6 593.2 618.6 323.7 26.4 1.4 1.5
9:15 10:15 11:15 12:15 1:15 2:15 3:15 4:15 5:15
Diagonal Wood x 3 (Short) 142.9 301.1 394.7 500.2 565.2 634.5 403.7 166.8 1.7 (NW/SE) 763.0 973.0 1130.0 1197.0 1167.0 1104.0 841.0 621.0 324.0
Diagonal Wood x 3 (Tall) 50.9 110.2 199.4 295.1 417.7 558.9 328.2 37.9 1.5
9:19 10:19 11:19 12:19 1:19 2:19 3:19 4:19 5:19
N/S Tatura x 3 191.5 440.8 530.8 598.0 610.9 533.8 323.6 64.9 1.7
- 654.0 986.0 1142.0 1205.0 1205.0 1038.0 832.0 571.0 271.0 N/S Ebro x 3 55.1 337.8 591.1 786.5 727.0 499.3 198.8 56.2 1.5
9:22 10:22 11:22 12:22 1:22 2:22 3:22 4:22 5:22
N/S Tatura x 4 83.6 217.3 287.3 314.0 334.7 298.9 100.2 6.2 1.7
- 816.0 992.0 1150.0 1205.0 1163.0 1027.0 820.0 563.0 260.0 N/S Ebro X 4 1.4 98.8 372.9 600.4 494.3 242.4 1.4 1.4 1.5
9:26 10:26 11:26 12:26 1:26 2:26 3:26 4:26 5:26 5:26
E/W Tatura x 4 180.9 234.4 263.1 295.1 277.8 244.5 177.2 75.7 1.7 1.7
- 808.0 1007.0 1164.0 1202.0 1158.0 1019.0 807.0 543.0 245.0 245.0 E/W Ebro X 4 315.3 352.1 377.2 341.7 296.3 293.2 164.1 82.9 53.5 66.9
9:28 10:28 11:28 12:28 1:28 2:28 3:28 4:28 5:28 5:28
E/W Tatura x 3 364.8 492.1 512.7 582.2 516.2 498.7 365.2 200.8 3.4 3.4
- 817.0 1051.0 1158.0 1211.0 1158.0 1007.0 797.0 534.0 239.0 239.0 E W E b r o x 3 463.8 582.6 601.2 587.4 549.2 519.7 361.5 202.4 95.1 111.4
52
FLAT BED SOLARIMETERS - 13 MARCH 1997 - GBHRS, 3LD - EASTERN STANDARD TIME
CALIBRATED DATA Fine, clear, 100% blue sky
i fine : fine fine ; fine i fine fine fine fine fine fine clear clear ; clear clear • clear , clear 1 clear clear clear clear
8:00 AM ! 9:00 AM i 10:00 AM! 11:00 AM NOON j 1:00 PM 2:00 PM 3:00 PM i 4:00 PM 5:00 PM i
i 1
7:45 8:45 9:45 i 10:45 11:45 12:45 1:45 i 2:45 i 3:45 4:45
N/S Triple Row (Standard) 44.0 77.4 185.4 322.4 332.0 297.5 248.4 145.6 9.6 1.3
- 340.0 489.0 714.0 856.0 1 i3Z0 840.0 811.0 623.0 413.0 200.0 N/S Triple Row (Tall) 14.0 18.1 42.5 122.1 130.1 95.9 11.1 8.0 0.8 0.8
7;51 8:51 9:51 10:51 11:51 1 12:51 1:51 2:51 3:51 4:51
N/S Double Row (Standard) 42.8 182.3 196.4 259.1 351.9 304.5 270.9 152.8 3.6 1.3
- 327.0 502.0 694.0 814.0 969.0 835.0 834.0 619.0 390.0 197.0 N/S Double Row (Tall) 1 35.3 96.9 200.4 334.1 440.8 1 3T6!9 232.2 108.8 0.8 0.8
7:57 \ 8:57 9:57 10:57 ' 11:57 12:57 1:57 2:57 3:57 4:57
N/S Cones x 4 rows (Standard) 71.0 191.8 322.4 412.0 \ 453.6 444.0 337.1 245.5 44.5 t^ - 346.0 515.0 705.0 820.0 859.0 833.0 t 682.0 602.0 336.0 191.0i N/S Cones x 4 rows (Tall) 58.9 136.0 306.2 456.2 513.8 415.9 253.6 150.5 49.6 9t,
8:00 9:00 10:00 11:00 !2:(X) 1:00 2:00 3:00 4:00 5.00
N/S Cones x 3 rows (Standard) 161.2 301.4 458.2 544.5 582.1 559.0 468.5 304.5 84.2 46.7
- 362.0 526.0 711.0 830.0 864.0 819.0 707.0 523.0 326.0 180.0 N/S Cones x 3 rows (Tall) 114.9 245.2 450.0 590.1 625.1 537.9 419.2 245.7 91.2 15.2
8:05 9:05 10:05 11:05 12:05 1:05 2:05 3:05 4:05 5:05
N/S Wood X 3 (Short) 31.6 142.9 304.2 444.2 552.9 405.6 126.6 110.7 3.6 1.3
- 384.0 540.0 723.0 832.0 930.0 809.0 683.0 564.0 329.0 175.0
N/S Wood X 3 (Tall) 25.0 34.7 198.9 437.8 539.3 297.7 127.6 4.8 0.8 0.8
8:08 9:08 10:08 11:08 12:08 1:08 2:08 3:08 4:08 5:08
N/S Wood X 4 (Short) 23.7 20.3 107.9 303.3 351.9 210.4 50.9 25.3 1.2 1.3
- 386.0 548.0 734.0 890.0 861.0 824.0 683.0 553.0 315.0 175.0
N/S Wood X 4 (Tall) 16.2 20.3 32.8 267.8 304.7 29.2 19.8 0.8 0.8 0.8
8:12 9:12 10:12 11:12 12:12 1:12 2:12 3:12 4:12 5:12
EAV Wood X 4 (Short) 36.1 72.7 97.0 134.9 161.3 177.8 183.4 162.5 98.7 25.3
- 398.0 563.0 840.0 835.0 857.0 807.0 672.0 544.0 307.0 147.0 E/W Wood X 4 (Tall) 16.9 21.7 26.8 27.2 18.8 0.8 26.9 62.4 66.4 27.9
8:15 9:15 10:15 11:15 12:15 1:15 2:15 3:15 4:15 5:15
E/W Wood X 3 (Short) 151.0 244.2 283.6 354.7 362.4 370.8 327.7 279.2 116.7 61.4
- 408.0 570.0 743.0 847.0 857.0 809.0 666.0 537.0 306.0 138.0 E/W Wood X 3 (Tall) 92.8 145.4 208.6 242.8 233.9 241.7 218.7 208.1 146.5 51.1
8:17 9:17 10:17 11:17 12:17 1:17 2:17 3:17 4:17 5:17
N/S Lincoln x 3 (Short) 82.3 257.3 432.7 545.7 571.6 474.2 302.8 127.6 1.2 1.3
- 431.0 583.0 749.0 837.0 894.0 803.0 692.0 515.0 275.0 135.0
N/S Lincoln x 3 (Tall) 36.8 136.7 376.2 554.1 537.8 372.9 168.0 15.2 0.8 0.8
8:20 9:20 10:20 11:20 12:20 1:20 2:20 3:20 4:20 5:20
N/S Lincoln x 4 (Short) 45.1 117.9 301.8 404.8 441.9 312.6 112.4 25.3 2.4 1.3
- 425.0 592.0 761.0 852.0 931.0 795.0 616.0 509.0 272.0 133.0
N/S Lincoln x 4 (Tall) 25.8 42.7 193.7 404.7 382.1 170.3 67.4 0.8 0.8 0.8
8:23 9:2.1 10:23 11:23 12:23 1:23 2:23 3:23 4:23 5:23
E/W Lincoln X 4 (Short) 125.1 207.3 235.1 292.6 316.8 325.4 292.2 213.0 83.0 32.8
- 437.0 601.0 763.0 847.0 852.0 795.0 664.0 500.0 244.0 116.0
EAV Lincoln X 4 (Tall) 36.1 102.7 114.0 157.5 172.3 166.5 165.6 166.5 84.8 30.3
8:26 9:26 10:26 11:26 12:26 1:26 2:26 3:26 4:26 5:26
E/W Lincoln X 3 (Short) 226.6 341.9 418.2 460.9 508.5 473.0 399.8 293.6 119.1 48.0
- 448.0 607.0 808.0 850.0 882.0 797.0 655.0 492.0 247.0 107.0 E/W Lincoln x 3 (Tall) 155.4 247.3 315.1 356.9 349.0 375.2 317.0 268.9 130.5 44.7
Refer to lig It readings for when cl judy, overc ast conditio ns may havf : occurred < uring the F 3S runs
53