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TRANSCRIPT
Irrigation Best Practice
A Water Management Toolkit for Field Crop Growers
This booklet may have been sent to you from Defra, using an address list maintained by the Division responsible for the June Agricultural Survey. No disclosure of identities or addresses of farmers has been made outside that Division.
Top Tips
Farmers and growers clearly recognise water as a valuable resource. However, as competition for it increases, it will be necessary to justify need and provide evidence of actual use, both for environmental protection and to meet crop protocol requirements.
• Define your water requirements based on local climate, soil type, crop and intended market
• Include water needed for crop quality, pest and disease control, damage minimisation, etc.
• Assess adequacy of supply, distribution and application equipment and identify areas for improvement
• Keep clear records of rainfall (and evapo-transpiration if possible), water usage, scheduling, operator training and equipment maintenance across all cropping areas (6 years minimum)
• Avoid windy conditions by irrigating at night, which also ensures maximum penetration of the root zone
• During windy periods set up rainguns to combat high winds
• Occasionally check operating pressures and water application uniformity during the growing season
• Check irrigation applications match the infiltration rate of the soil to avoid unnecessary erosion
• Don’t rely on memory. Carry day sheets or field book to record each irrigation “event” as it happens
Contents
Page
1 Introduction 1
2 Background 2
3 The need for water and how much to apply 4
4 Applying irrigation efficiently 11
5 Monitoring water usage 19
6 A toolkit for efficient water use 31
Checklist of forms included
Basic farm irrigation informationAbstraction licencesMeter readingsIrrigation summary for the yearEnvironmental concernsTraining recordsAnnual rainfallMaintenance recordsDay sheet – Irrigation applicationsDay sheet – Maintenance checks
1 Introduction
All farmers and growers recognise that water use and supply is an essential factor in crop production. A reliable and consistent supply of water is vital to maximise both yield and quality, and it is important that water is applied at the correct time, in the right quantity and with the minimum of waste.
In recent years, supplies of water have frequently become stretched, and everyone now recognises the need to conserve supplies. Changes to the arrangements for abstraction, and placing irrigation under licensing control, have meant that farmers and growers need to pay even closer attention to the way in which they use water. There are sound business and environmental reasons why water use should be considered carefully at all stages of the production cycle.
Careful and effective water management will be critical to profitable cropping in the future. This booklet and its accompanying CD will help you by giving practical advice that you can use every day. It will help you to monitor your overall water use, advise on how to plan for the future and will show how savings can be made. It is possible that demand for water, and its cost, may increase in the future, and we all need to be able to make the best of a finite resource. The water audit toolkit will show you how to make the most of your water.
Domestic Horticulture and Potatoes TeamDepartment for Environment, Food and Rural Affairs
July 2007
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2 Background
The transposition of the EU Water Framework Directive into UK law, increasing competition for water (from all users), the recently unpredictable nature of our weather patterns and the threat of climate change, have all highlighted the importance of sustainable water sources for agricultural irrigation.
It has been estimated that the demand for irrigation water, particularly in southern and eastern England, could rise by 20% by 2020. One climate change scenario suggests that summers like 2005 & 2006, during an 18 month “dry spell” for southern England when only 75 % of normal rainfall was received, could become normal by 2040 and that weather extremes will be more common.
The Water Framework Directive (WFD) aims to achieve improved environmental protection though greater control over water quality and usage. This will have far reaching implications for the agricultural and horticultural industries, with the requirement to justify water need and its sustainable supply. In addition, the 2003 Water Act changed the nature of abstraction licences, and these changes, acting in concert with concerns raised by the WFD, may well affect the ability of farmers to continue to irrigate.
It is therefore evident that potato and vegetable producers will have to use water with great efficiency in the future. Accurate scheduling and effective management and maintenance of systems will be crucial to achieving the best use of water and in demonstrating the continuing need for crop irrigation.
The aims of this toolkit are to assist those irrigators who currently do not keep records of their water use, but who nevertheless are concerned with the reliability of future water supplies, to manage their use of water more effectively by:
• Understanding the relationship between crops and their need for water• Quantifying the water requirement for yield, quality and management• Keeping records of actual volumes abstracted• Knowing how to assess the performance of an irrigation system and the alternative
equipment options available• Ensuring all equipment is appropriate for the job to be done and operated efficiently
Simply, this booklet contains:
• advice to enable water use to be planned, and • a simple, structured means by which farmers and growers can keep their own
records This second part has been done by providing:
• Simple templates to assist regular record–keeping• Straightforward spreadsheets that enable more detailed records to be kept and farm
irrigation water use to be managed more effectively (on an enclosed CD)
Collecting this information routinely will build a picture of water use on the farm, and the way in which it is managed, and so provide a basis for improvement.
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Planning water use
At first sight, planning water use on-farm may seem a tricky operation, given our lack of control over the weather. However, many benefits can be realised from setting some time aside to examine the whole process of planning water sources, distribution and usage.
For most vegetable and potato crops on many soils, irrigation is a necessity, to ensure timely production of crops to the specification demanded by the market. However, seasons vary and with it irrigation demand; the crop area, location on the farm and soil type will also affect water requirements from year to year. The large area of these crops grown on rented land can also pose challenges, with often little more known at the outset than the total amount of water that may be available. Detailed consideration is essential to get the most effective use of water by organising water supply, distribution systems, application equipment and scheduling to work harmoniously together. Though this may entail some investment in time and/or capital, experience gained from this approach will enable opportunities for improved practice to be identified. Planning for improvement also means trying to find some time in the season to appraise performance and to record areas where adjustment or improved practice will make savings or lead to better performance.
In addition to optimising water use to benefit crops, competing requirements from other water users and the environment mean that farmers and growers increasingly have to justify their requirement for water and have to demonstrate that it is being used efficiently. At the core of any plan for water use, is the need to match potential crop requirements with a suitable source of water at the right time.
The templates at the back of this booklet (which can be photocopied) and/or the spreadsheet tools on the CD inside the back cover can support you in planning and managing your irrigation water resources.
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3 The need for water and how much to apply
Plants suffer stress when they cannot get enough water. Drought stress causes the closure of the leaf stomata, which restricts photosynthesis and thereby reduces growth. Irrigation should be applied to prevent drought stress occurring.
Three main factors affect crop water supply:
• The level of water demand, expressed as evapo-transpiration (ET)• The amount of water in the soil• The ability of the root system to extract water from the soil
Evapo-transpiration (ET) or total water loss
The total water loss, i.e. the demand for water, is referred to as evapo-transpiration (ET), and consists of both transpiration from plants (crop ET) and evaporation from the soil surface and air (ET0). ET is usually calculated from meteorological data and is expressed as the daily rate of water used in mm. ET data are available from sources such as the Meteorological Office, the internet, and by using in-field or on-farm ET gauges and computerised irrigation scheduling programs.
• The scheduler tool in the accompanying CD has daily regional estimates of ET for the irrigation season built into it. (Values can be replaced by data from other sources if required)
The water held in the soil
The amount of water that soil is capable of retaining depends on its texture (the particle sizes) and structure (how the particles are arranged). In a saturated soil, all spaces between particles are filled with water, but drainage progressively removes water from the larger pores between particles first. After a few days drainage, the only water left is that contained in pores sufficiently narrow that forces holding it around the soil particles are in equilibrium with that due to gravity. This stage is known as ‘field capacity’ (FC) and represents the upper limit of available water in the soil. Eventually, as drainage and crop extraction proceed, a point is reached when the plant cannot extract any more water (the permanent wilting point or PWP). The soil water available for the crop is the therefore the amount held between FC and PWP and is described as the available water capacity (AWC): thus AWC = FC – PWP.
Sandy soils hold relatively little water as their texture (predominance of larger pores) allows water to drain freely down the soil profile, and these soils have a small AWC. Heavier loam and clay soils are equally porous by volume, but because this pore space is composed of much narrower pores, they are able to retain more water against gravity. These soils have a larger AWC.
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The AWC of soils can be divided into three classes: low, medium and high for irrigation response purposes.
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A LOW
AWC not more than 12.5 % of the soil
Typical soils are Breckland in Norfolk and Suffolk, Bunter sands of Nottinghamshire, Suffolk coast sandland, Cannock Chase, and ‘brashy’ soils of the Cotswolds and Lincolnshire limestone. In most cases the land is naturally well drained and fields lack perimeter ditches
B MEDIUM
AWC 12.5 – 20 % of the soil
All other soils
Coarse sand Loamy coarse sandCoarse sandy loam
SandLoamy sandFine sandLoamy fine sandClaySandy claySilty clayClay loamSandy loamSandy clay loamSilty clay loamFine sandy loamLoam
C HIGH
AWC greater than 20 % of the soil
Typical areas are the Cambridgeshire Fens, “carr” land in the Humber-Trent lowlands, Lancashire “mosses”, the “warpland” of the lower Trent/Humber, brick-earths of North Kent, the Sussex coastal plain, and south-east Essex
Very fine sandy loamLoamy very fine sandVery fine sandy loamSilt loamSilty loamPeaty soils
• Most soil types are in class B
Soil moisture deficit (SMD)
• Soil Moisture Deficit (SMD) is an indicator of the moisture status of the soil and is the key measurement used in irrigation scheduling
When water is lost from the soil by evaporation and transpiration, the water content is reduced and a SMD develops (below FC). These processes tend to extract the water from the larger pores first, because it is held less tightly by the soil. As these processes continue, only the tightly retained water remains, and eventually the plant responds by closing stomata, thereby reducing water loss. The point at which this occurs is known as the “critical SMD”, as closing stomata results in lower rates of photosynthesis and potentially lower yields. If the soil is allowed to dry beyond the “critical SMD”, the rate of water uptake decreases and plant growth is compromised
• The SMD should be monitored and irrigation triggered before it reaches a critical level
• Suggested trigger SMDs and irrigation requirements for common field crops are given in the Table below
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However, it is important to note that the amount of irrigation that should be applied at any one time is limited both by the current SMD and the infiltration rate of the soil, i.e. irrigation should not be applied at a faster rate than can be accepted by the soil. For example, if irrigation is to be applied at an SMD of 20 mm there is no benefit from applying more than 20 mm of water. It is usually sensible to apply less than this, say 15 or 18 mm, so that there is spare capacity in the soil should rainfall occur after irrigation has been applied (though amounts below 18 mm are considered impractical for rainguns). Irrigating with more water than the soil can accept is not only a waste of resource, but likely to cause drainage, run off and erosion.
Irrigation Schedule Times Response Periods and Trigger Application
Crop Response periods Irrigation plan for 3 soil typesmm of water at mm SMD
Potatoes
Pre-sowing or planting irrigation
Growth stage Time of year ALow AWC
BMedium AWC
CHigh AWC
For example idealised schedules refer to Irrigation Best Practice Water Management for Potatoes: A Guide for Growers ADAS/Defra December 2005
Asparagus See non-yield irrigation requirement
Beans, broad Early flowering & mid May to 20 at 25+ 20 at 25+ 20 at 25+ at pod swelling early July
Beans, Dwarf April/May Early flowering June to August 20 at 25+ 20 at 25+ 20 at 25+ green bud stage & pod swellingBeans, climbing April/May Early flowering June to August 20 at 25+ 25 at 30+ 40 at 50+ onwardsBeetroot April to June Throughout May to August 20 at 25+ 25 at 50+ 25 at 50+
Brussels sprouts May to June for When lower August to 35 at 40 35 at 40 35 at 40 establishment buttons 15-18 mm October diameterCabbage, July to August 20 days before April to May 18 at 20 20 at 25 20 at 25 spring hearted harvestCabbage, greens July to August Pre-drilling and May to 18 at 20 20 at 25 40 at 50 to establish September transplantsCabbage, April to July Pre-drilling and May to 18 at 20 20 at 25 40 at 50 summer & to establish Septemberautumn transplantsCabbage, winter April to July Pre-drilling and April to July 18 at 20 20 at 25 40 at 50 & Savoy to establish transplantsCarrots April to June Throughout June to 20 at 25 40 at 50 SeptemberCauliflower, Throughout or 25 April to June 18 at 20 20 at 25 early summer mm when 50% of plants 30 mm curd diameterCauliflower, Throughout or 25 May to 18 at 20 20 at 25 50 mm 20 summer & mm when 50% September days beforeautumn of plants 30 mm harvesting curd diameter startsCauliflower, May to June After planting to July 25 at 40 25 at 40 25 at 40 winter establish
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Irrigation Schedule Times Response Periods and Trigger Application
Crop Response periods Irrigation plan for 3 soil typesmm of water at mm SMD
Pre-sowing or planting irrigation
Growth stage Time of year ALow AWC
BMedium AWC
CHigh AWC
Celery June Throughout June to August 18 at 20 20 at 25 20 at 25
Courgettes April to May Throughout June to August 20 at 25 20 at 25 20 at 25
Lettuce, summer April to August Throughout April to 18 at 20 20 at 25 25 at 50 September
Leeks April to July Throughout May to August 20 at 25 25 at 50 25 at 75
Onions, Bulb, Throughout May to July 20 at 25 25 at 40spring sown/planted
Onions, salad April to September Throughout April to 20 at 25 20 at 25 20 at 25 September
Parsnips See non-yield irrigation requirement
Peas, green & April to May At early flowering, June 20 at 30+ 25 at 30+ 25 at 40+ vining then at pod swellingRadish April to August Throughout April to August 20 at 25 20 at 25 20 at 25Spinach April to July Throughout to May to August 20 at 25 20 at 25 20 at 25 AugustSwedes May to June Start of root June to July 20 at 25 20 at 25 50 at 75 swelling onwardsSweetcorn June Throughout June to August 25 at 50 25 at 50 50 at 75Turnips April to July Start of root June to 20 at 25 20 at 25 50 at 75 swelling onwards September
Non-yield requirements for irrigation
Irrigation increases crop yield over and above rain-fed production, but crop quality is often of even greater importance to the business, and is normally specified as a condition of contract and sale. Irrigation should not be solely be linked to yield when being planned.
For example, some crops are irrigated at germination and seedling stages to assist establishment and to ensure uniformity and continuity of supply. Timely irrigation can also suppress many diseases, pests and disorders, though their occurrence and severity is of course affected by other factors such as variety, location, nutrition, soil type, etc. However, over-irrigation can encourage some disease problems (see Table opposite).
For each crop type, the additional amount of water which could be required for crop specification / quality purposes, and its timing, is indicated in the table below.
• Water applied for crop quality and soil management purposes should also be accounted for in irrigation scheduling and planning in the attached spreadsheet tools
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Crop Reason for Amount When Other Quality irrigation Issues
Asparagus Plant establishment of modules Up to 3 June applications of 18 mm
In dry periods during harvesting water Up to 25 mm April and may be required to aid emergence of May spears and to minimise mis-shapes
Normally, avoid irrigation during harvest as this can have adverse effects on spear quality
Beetroot For plant establishment on light soils in Pre-sowing up April to dry conditions to 25 mm June
Scab control Maintain SMD at July to less than 18mm September on light soils
Broad beans Irrigation can be associated with increased risk of chocolate spot
Cabbage spring After application of fertiliser top Up to 18 mm dressing in dry conditions
Carrots If soils are very dry at drilling irrigation April to July should be applied to ensure the availability of moisture to the seed
Before and/or after plastic cover 1 or 2 April and removal applications of May 18-25 mm
Common scab in dry years Irrigation can July to give some September control. Maintain SMD at less than 18 mm
The production of baby carrots Respond to May to (Chantenay) at high densities irrigation right September through to harvest
Cutworm damage 20 mm when Early-mid risk highest July
Irrigation following a large SMD may increase splitting
Cauliflower Crops under plastic covers Prior to or on May removal to aid lifting of polythene
Dwarf beans Deliberate moisture stressing at start of flowering can shorten flowering period and give more uniform bean size
Crop Reason for Amount When Other Quality irrigation Issues
Lettuce Establishment of blocks/modules in dry 12 mm at 2 or 3 April to weather day intervals August after planting
Celery Essential for quality and succulence
Bulb onions Germinating seed vulnerable to 10-18 mm April and desiccation when the radicle emerges required if May from the seed coat drying conditions experienced
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Tipburn Frequent small May to amounts of water August if crop under stress
Cutworm damage 20 mm when Early-mid risk highest July
Minimising duration of leaf wetness will reduce disease risk
Allow soil to dry out in the run up to harvest (from end July) to avoid delay to bulb ripening and to improve keeping qualities
Excessive irrigation can lead to bacterial & fungal diseases
Salad onions Minimise duration of moisture on foliage to reduce disease risk
Parsnips For plant establishment of late sowings May and in dry conditions June
Before and/or after polythene removal 1 or 2 May applications of 18-25 mm
Cutworm damage 20 mm when Early-mid risk highest July
Aiding harvest in prolonged dry weather Up to 25 mm September and October Peas Irrigation at petal fall increases risk of Botrytis on the pods
Potatoes Common scab control Amount depends 4-6 weeks on variety and following crop growth tuber stage initiation Cutworm damage 20 mm when Early-mid risk highest July
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Crop Reason for Amount When Other Quality irrigation Issues
Potatoes Irrigation and blight control programmes need to co-ordinated. Also, excessive irrigation may encourage an increased risk of rotting and raised lenticels)
Irrigation can either encourage or suppress many other diseases, pests and disorders. For detailed guidance refer to Irrigation Best Practice Water Management for Potatoes: A Guide for Growers ADAS/Defra December 2005
Turnips Irrigation 10 to 18 days after drilling can depress yield
Attention to detail and regular checks are essential to ensure that irrigation is applied:
• In the right quantity at the right time • Uniformly across the crop area• With minimal waste
How much water and when?
The basis of determining the quantity of water required has been discussed in Section 3, but a knowledge of when this should be applied is dependent on measurement of the soil moisture deficit and subsequent scheduling of irrigation applications. Recent data shows that around 40% of irrigators still do not use any form of scheduling, which should form the basis of planning water use during the irrigation season. It would be unwise to rely solely on scheduling without examining soil in the field, but equally basing irrigation decisions subjectively on gut feeling, experience or walking the crop, will not ensure optimum water application or crop response.
More information on methods and tools for measuring soil moisture deficits and on scheduling irrigation for crops can be found in the companion Defra booklets on Irrigation Best Practice, ‘Water Management for Field Vegetables’ and ‘Water Management for Potatoes’. A simple scheduler is included with this booklet (see Section 6 for further details), but it must be stressed that this should be operated in conjunction with regular field visits to ensure that the predicted water balance does not deviate from the actual conditions at site.
It must also be stated that better scheduling models are also available to make use of the site and crop specific information obtained from the instrumentation mentioned in the above literature. Our scheduler uses estimates of ET from long–term weather data, and as such will deviate from actual values year to year. Measured values will always be more accurate. In addition, our scheduler does not change ET according to crop, which more complex models often include. This is another reason why slight differences between real and predicted SMDs may develop as the season progresses.
Uniformity of application across the crop area
Poor irrigation uniformity - a waste of both water and energy
Irrigation should be applied as evenly as possible to ensure a uniform crop response. Variable applications lead to over-watering of some areas in an effort to ensure that other parts receive an adequate amount; this in itself can also lead to lower crop yield and poorer quality, as well as creating surface water ponding and possible run-off problems.
Uniformity is very difficult to measure visually, so can easily be overlooked. However, application uniformity should be checked periodically to identify any spatial variability that may have arisen since the last check. Then the set up (e.g. lane spacing, etc.) and operation (e.g. water pressure) of the system can be checked, and improvements made as necessary.
Uniformity is influenced by three main factors:
1. Correct operation of equipment (pressure, trajectory & sector angle)2. Lane spacing – the area of wetted overlap (how far the water is being ‘thrown’)3. Local weather conditions, including wind speed and direction during irrigation
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4 Applying irrigation efficiently
Most farmers still use rainguns fitted with hose reels because they are flexible, robust and fit in well with the rotational pattern of cropping in the UK. The following section provides guidance to those farmers on how best to set and operate these systems. A brief consideration of alternative systems available then follows.
Getting the best from rainguns
Most irrigation is still applied through rainguns and it is vital that these are operated at their design pressure to provide a good distribution of many small droplets that will land gently and percolate through the soil. When pressures are too low, larger droplets are formed, which can cause soil capping or erosion.
All raingun nozzles have a design pressure that is linked to a water throw radius. This can be found in instructions provided with the machine. As a general guide, the pressure needed at the raingun (not the hose-reel) will be approximately 4.5-5 bar, and a spigot is usually fitted on the riser of the raingun trolley so that a pressure gauge may be attached.
• It is worthwhile fitting a gauge here to ensure that the correct pressure is being achieved at the raingun
There is always a pressure gauge provided on the intake to a hose-reel and this should also be checked to ensure that water pressure at the machine matches the manufacturer’s recommendations. This value will vary depending on the machine, and may be between 8-10 bar, though some more recent machines may have hose-reel connection pressures of as low as 5.5 bar, dependant on use.
Trouble-shooting low pressure
The main reasons for low pressure are:• Raingun/nozzle size – incorrect initial selection: too large will allow too much water
outflow and not permit adequate system pressure rise to achieve the desired trajectory. In addition, applying water though rainguns at amounts greater than 25 mm per pass may aggravate the overall pressure/flow balance within the system, causing instability of the machine, which may in turn cause problems during reel wind-in.
• Pipe size – In narrow bore pipes, frictional pressure from the pipe wall reduces flow rate in the pipe for any given pump pressure. To maintain flow rates therefore, pump pressures have to be increased. (See Table on next page).
• Pipe lengths – As length increases, more pipe is in contact with water and thus more energy is needed to offset the increased friction. This is often a problem with ‘new’ fields further away from the pumping source.
• Land contours – Every 10 m rise in the land is equal to 1 bar pressure within the pipe. This must be considered when laying out pipes for seasonal use or when planning the routing of any system. Pressure is of course increased within the pipe for a downhill slope in the land surface (an extra 1 bar for a 10 m fall).
• Pump – incorrect speed: poor pump selection or worn components can all result in reduced water pressure. Excessive suction lift at the water source can also limit pump performance.
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Pipe sizes and lengths
Energy is lost within distribution pipework due to the friction of water passing through it, but a good design should allow for no more than 10% of the pump energy to be lost through friction (in addition to the equipment connection pressure and any lifts involved).
• Select the largest internal diameter pipe (that is consistent with cost and other practical factors) to minimise friction losses and reduce energy consumption
Pressure loss due to pipe friction
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Pressure loss (m per 100 m pipe)
Pipe internal diameter Water flow Water flow (mm) 15 litre per second 30 litre per second
100 2.8 10 150 0.5 1.5 200 0.12 0.3
Note: 10 metre pressure = 1 bar (1 atmosphere) All pipes sizes should be checked to make sure it is the internal diameter which is used for calculations.
Examples of the amount of energy used (expressed as head losses) at two flow rates and for three internal pipe diameters are shown in the above Table. It can be seen that the energy does not relate linearly to pipe diameters, which means that for a relatively modest increase in diameter, the pressure loss drops considerably. There is only 15-20% reduction in pressure loss for a 50 % increase in diameter (from 100 to 150 mm), but a 95-97% reduction for a doubling of diameter (from 100-200 mm).
• Most growers have to accept some constraint on where crops are grown and how water is delivered to the field. However, good planning should ensure that the furthest locations will be served by the largest affordable diameter pipe.
• Block cropping will concentrate the demand on the distribution system, so operators need to consider whether pipe size is large enough for the demands of such a layout.
• A ring system design allows water to flow within the ring circuit in either direction at lower flow rates within the pipe. This lowers energy consumption due to friction, and provides more pump energy for the irrigation equipment.
Pump
All pumps have an operating ‘window’ in their original specification to optimise flow rate, pressure, operating efficiency and power input, and this is designed around a fixed operating pump speed.
• Check the pump isn’t operating outside this window, trying to supply a volume of water in excess of its capacity, to meet the needs of too many hose-reels or nozzles
Lane spacing
All hose-reel / raingun combinations can work at varying lane spacings. This is listed within
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the equipment instructions. Operators in the UK commonly select a lane width of 72 m, which allows the raingun trolley, or sledge, to follow pairs of potato rows or one bed. Little damage to crops is normally caused, though increased attention is being paid to this potential problem, especially for high value crops (e.g. with offset equipment).
Other growers now leave these rows unplanted, accepting the production loss is balanced by the reduced amount of grading out required.
• It is critical that the lane spacing remains unaltered during irrigation and all adjustments to the equipment permit correct overlap of water from lane to lane at 72 m. Generally this means that the water should have a throw of approximately 43 m.
Checking water distribution
• Check in the field using 5 litre catch cans, spaced at 3 m intervals across the full wetted area, and covering the overlap of adjacent pulls. Measurements of the volume of water collected at each point can then be plotted to show the areas of non-uniformity on a graphical image (see below).
• A value called the Coefficient of Uniformity (CU) is calculated from these measurements. The larger the figure, the more even the application - though much higher than 90% would not be expected in the field.
• If gun pressure is poor then the following pattern - taken from a field study - may result. This poor distribution will result in a greater cumulative disparity in the SMD if repeated over time.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Poor raingun overlap due to low pressure
35
30
25
20
15
10
5
0
Water appliedmm
Gun Gun
• A correctly set up raingun with correct operating pressure at the gun to match the chosen lane spacing, produces a much better performance (see over) – also a field study result
72 m lane spacing, CU = 63%
A suitable CU target for rainguns is 80-85%. Simple checks to uniformity - and the amount actually applied - may be found by using a number of simple rain gauges, or ‘catch cans’ (see box below). Results greater than 75% are acceptable but lower figures show scope for improvement.
Calculating the Coefficient of Uniformity (CU)
The CU can be calculated by carrying out a simple field interception of water across an irrigator’s wetted area. This is done out by putting out ‘catch cans’ – normally 5 litre paint pots at 3 m intervals to ensure that the whole distribution is intercepted.
The interception area (opening) of the ‘can’ must be known, so that the ‘depth’ of water collected can be calculated from the measured volume in the can. For instance, a can with an opening of 20 cm diameter (radius of r = 10 cm) will have an area of 314 cm2 (area = πr2) (π = 3.142), and so 10 mm of rain will give a volume of 314 ml in the can (1 ml = 1cm x 1 cm2 but 1 cm = 10 mm) (rainfall is usually expressed in mm). Therefore the volume of ‘rain’ in the can (measured as ml or cc) should be divided by 1/10 of the area (cm2) to obtain the depth of rain in mm.
For a 72 m raingun lane width, the wetted area (assuming no side wind effect) will probably be around 85-90 m in width. Thus around 30 cans will be required, placed at right angles to the irrigator travel direction as it is drawn across the field. Once the irrigator has passed over the line of cans, the volume of water in each can is measured using a graduated measuring cylinder, and the volume recorded for each can. The volume per can must then be calculated into a depth per can by dividing by the known collecting area (opening size) (see above).
The Coefficient of Uniformity (CU) as a percentage can be calculated using the formula :
CU = (1 – (∑ (x – xm)) / y) x 100
where, ∑ means the sum of the following e.g. ∑x = x1 + x2 + x3 …xn
n = number of cansx = depth of ‘rain’ found in each can (mm)xm= mean depth (mm) for all cans (xm = ∑x / n) y = total of depth (mm) from all cans (y = ∑x)
and (NB) x-xm is always expressed as a positive value (e.g.if x=5 and xm=6 then 5-6=1 not –1)
Fewer cans can be used, but the result will be less accurate.
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Good raingun uniformity at correct pressure
Water appliedmm353025201510
50
Gun Gun1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
72 m lane spacing, CU = 90%
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Mitigating wind effects
The irrigation season in the UK includes many days of windy weather, when waiting for still conditions may not be feasible. To reduce the effect of wind on uniformity, farmers should aim to:
• Set the raingun sector angle at 210º or more (rather than the normal 180º). This allows the raingun to cover the ends of the cycle for longer, depositing more water at the edges of the lane width. Any risk of possible overwatering is more than outweighed by better distribution in windy weather.
• Make the most of the opportunity to irrigate at night, when the mean UK wind speed is about half of that found during the day.
• Plan to include most of the longer “pulls” at night, where possible, so that a greater area receives water more uniformly.
• Where newer ‘variable angle’ rainguns are used, lower the angle (to around 15º from the horizontal, compared with the normal angle of around 22º) when the weather is windy. In calm conditions these guns may be increased to a 25º angle to maximise throw, thus achieving good overlap.
• On exposed sites, better uniformity can often be achieved by adopting a lane spacing narrower than 72 m. This may, in turn, affect other farm operations such as spraying and fertilising, but often 60 or 66 m spacing can offer improved application uniformity.
Alternatives to Rainguns
Booms
Boom equipment offers more even water distribution than a raingun, and regularly operates at a CU of 90%. This is mainly because a boom carries a large number of small nozzles or sprinklers. Thus, the trajectory for droplets to the soil is shorter and good overlap along the boom profile is achieved. Booms will generally produce a larger number of small droplets, which create less damage to soil and plants, due mainly to the droplets having less energy. When compared to raingun use, booms tend to result in more uniform and higher quality crops with cleaner foliage.
However, booms do not ‘throw’ water from the unit as far as a raingun, and this reduction in the wetted front as the boom moves means that the soil must accept the water over a shorter period if operated at the same forward speed and application rate. On a few soil types this can be a problem, such as soil with a high silt content or where slopes are significant, i.e. over 5%.
Field obstructions such as poles or trees are challenges to boom usage, as are fields with a variable geometry. However, it is worth checking just how much of the field area is affected, as often the proportion can be quite small. In addition, booms can be supplied with a central raingun so that where obstructions are found the booms may be folded and the raingun used.
Although the cost of boom equipment tends to be more than for a raingun, when considered over a 10 year life (including extra labour costs) the extra cost per hectare can be recouped
17
in crop quality and yield improvements. In addition, booms operate at a lower pressure than rainguns (around 3 bar), which results in energy savings. This may become more important in the future as energy costs rise.
Sprinkler and drip irrigation
Mobile sprinkler systems requiring hand movement between applications are not very common. They can be used on small areas i.e. awkward field extremities, vegetables or hardy ornamental stock. “Solid set” or fixed sprinkler systems are more common, as they almost eliminate seasonal damage to the soil or crop and provide good uniformity. The recent availability of single moving part sprinklers with laterals typically spaced at 18 m and with good uniformity characteristics, may herald a renewed interest in sprinklers.
Drip or trickle irrigation systems normally place the water directly into the soil, or onto the soil surface, giving minimal risk of run-off. All drip systems can accommodate growing techniques with little or no modification, and field lengths are not normally a problem due to the availability of pressure compensating systems. Drip irrigation involving soil surface or buried pipes is unaffected by wind and, in addition, places water close to the rooting zone (limiting evaporative loss). A correctly designed and installed system should easily achieve a CU above 90%. However, these systems are highly susceptible to poor management, with consequent impacts on uniformity.
Drip irrigation is well suited to multi-season cropping such as soft and top fruit. Where it has been used for field scale arable row crops or vegetables, the cost and practical issues of pipe installation and retrieval currently challenge its more widespread adoption.
Soil surface management
Soils vary in the rate at which water can infiltrate. Water should not be applied at a rate faster than the soil can absorb it, or in a manner that damages the soil surface. In either case, water will pond and soil erosion could follow. Interception can be improved by cultivation systems where the soil tilth is left slightly rough (or as a pressed surface if this is more appropriate).
There are a number of ways in which water interception can be improved: (These are particularly important for unstable soil types and sloping ground.)
• Compaction and rutting from previous traffic should be minimised• Tyres and pressures should be chosen to suit loads being carried, to exert as low a
ground pressure as possible • Compaction avoidance should be part of a strategic soil plan for any business. Once
caused it is normally difficult to correct, because of a lack of opportunity, or power for subsoiling (as well as the cost)
• Maintaining the correct raingun pressure will ensure correct atomisation at the raingun and limit the production of large droplets
• Boom irrigators produce a larger proportion of fine droplets, which reduces erosion risk• Growing crops in flat-topped or centre-dished beds allows the soil to receive the water
with less run-off and erosion risk, and some extra benefit follows from more water being held in the soil and available for root uptake
18
Slopes
Sloping land, particularly when compacted by wheelings, will lead to water run-off. All irrigation layouts should be assessed for the amount of surface run-off produced, and, where sloping land is present, the differences in infiltration rate between different soil types may be accentuated. Where practical, crop row or bed alignment across a slope should be adopted to limit run-off.
Special equipment
Run-off can also be limited by the use of tied ridges. These are small dams of soil formed approximately every metre to bridge the gap between beds. These hold irrigation water and rainfall and allow it to then infiltrate slowly into the soil. Slopes as steep as 10o have shown good water retention following the use of tied ridges. The frequency of these tied ridges along the row ensures that retained water does not accumulate in a large enough mass to start erosion by itself. A simple front mounted single tine or hoe on the harvester tractor can then be used to break down the dams and thereby allow the harvester passage.
One particular cultivation tool developed to assist infiltration is the “Aqueel” (Simba International Ltd.), which can be used over the whole soil surface, a raised bed surface, or on the top of potato ridges (see picture). Small depressions are created on the soil surface, which act as reservoirs (of about 1 litre) to intercept the water and thereby allow infiltration into the soil with less chance for lateral displacement and run-off. Just under 200,000 mini reservoirs are formed per hectare and the effect may persist over the whole season, depending on soil type and amount of water intercepted. The polymer wheels are self-cleaning and can be fitted to cultivators, bed formers, drills and planters.
19
Record-keeping of water use
A comprehensive farm irrigation water plan should have a number of aims but with all of them contributing into an overall objective of improving farm management and profitability. The primary need of the plan, though, is to simply keep an accurate record of water used on the farm. From this set of records, many other benefits will follow, in particular a plan should be able to: • Record actual water use compared with planned, and so provide a basis for increasing
efficiency• Demonstrate the responsible use of water • Take account of environmental considerations such as SSSIs• Meet the requirements of Crop Assurance Protocols• Provide a comprehensive record of management and staff training
There is an increasing likelihood that such record keeping will become commonplace on farms in the future, and a greater reliance placed upon it when demonstrating the environmentally responsible and sustainable nature of farming to the wider community.
Templates to help you
Basic Farm Irrigation Planning
The range of information that it is advisable to keep falls into two categories. The first can be considered the minimum set of background information that will be useful accumulated over many years to demonstrate the efficient use of water on farm, and help to justify the need for water for crop production at that location. Such a dataset may comprise the information listed below:
Background information
• Farm information; including soil types and cropped and irrigated areas• Abstraction licence information; licensed amounts and rates for abstraction, together
with actual amounts abstracted; should include stored water as well as seasonal• Actual meter readings to calculate above information and for licence checking (how
much water the business is actually using)• Annual summary of irrigation water applied and on which fields and crops (including
that for aiding germination, transplanting / crop establishment and harvesting), including dates of application
• Soil management and environmental considerations• Training records of all operators
There is a need to demonstrate that appropriate training is undertaken by both those who manage irrigation and by operators. Annual training records, including certificates of attendance, will be valuable in demonstrating water use efficiency and in supporting irrigation abstraction licence renewal. In addition, a map should be kept showing the location of water courses, reservoirs, conservation areas, nature reserves, SSSIs, etc.
5 Monitoring water usage
20
Bas
ic F
arm
Info
rmat
ion
Gen
eral
Far
m Ir
riga
tion
Info
rmat
ion
Trad
ing
Title
Farm
Add
ress
Tota
l far
med
are
a (h
a)
Irri
gate
d ar
ea (h
a)
Very
ligh
t/lig
ht la
nd (h
a)
Med
ium
land
(ha)
Hea
vy la
nd (h
a)
21
Abs
trac
tion
licen
ces
Year
:-
Site
Li
cenc
e Li
cens
ed
Hou
rly
Dai
ly
Star
t En
d Q
uant
ity
% o
f C
onfir
mat
ion
of
Num
bers
Q
uant
ity
Abs
trac
tion
Abs
trac
tion
met
er
met
er
used
m3
licen
ce
com
plia
nce
with
any
(S
umm
er/
m3
m3
m3
read
ing
read
ing
us
ed
spec
ific
licen
ce
Win
ter)
m3
m3
requ
irem
ents
Win
ter
stor
age
(Per
iod
: -
)
Rese
rvoi
r na
me
and
Volu
me
at s
tart
of
Volu
me
at e
nd o
f Q
uant
ity u
sed
m3
% o
f cap
acity
use
dC
apac
ity m
3 se
ason
m3
seas
on m
3
Tota
l wat
er a
vaila
ble
22
Met
er r
eadi
ngs
Met
er n
umbe
r D
ate
Read
ing
Cur
rent
cer
tifica
te o
f
calib
ratio
n (r
enew
al d
ate)
?
Not
e: R
ecor
ds s
houl
d be
kep
t of a
ll m
eter
rea
ding
s fo
r at
leas
t 6 y
ears
23
Irri
gatio
n su
mm
ary
for
year
: -
Ir
riga
tion
amou
nt a
pplie
d an
d da
te a
pplie
d To
tal
ha ir
riga
ted
Fiel
d no
./na
me
mm
da
te
mm
da
te
mm
da
te
mm
da
te
mm
da
te
mm
da
te
mm
‘0
00 m
3 *
Cro
p (in
sert
)
Cro
p to
tal
Cro
p (in
sert
)
Cro
p to
tal
Cro
p (in
sert
)
Cro
p to
tal
Farm
tota
l
Tota
l qua
ntity
ava
ilabl
e
Diff
eren
ce (i
f any
)
*Tot
al m
m x
ha
on w
hich
irri
gatio
n ap
plie
d ÷
100
= ‘0
00 m
3
24
Envi
ronm
enta
l con
side
ratio
ns
Dat
e
Envi
ronm
enta
l con
cern
A
ctio
n ta
ken
By w
hom
R
oof a
nd y
ard
run-
off
So
il er
osio
n e.
g. u
se o
f tie
d ri
dges
alo
ng th
e fu
rrow
bot
tom
s
R
un-o
ffs fr
om m
anur
e he
aps/
slur
ry/s
eptic
tank
s
D
isch
arge
s fr
om o
ther
pro
cess
es
Le
achi
ng
e.g.
not
app
lyin
g to
o m
uch
wat
er o
r ap
plyi
ng
it un
even
ly
O
ther
(spe
cify
)
25
Trai
ning
rec
ords
Trai
ning
rec
ord
Dat
e
Title
/pur
pose
e.g
. sch
edul
ing,
saf
ety
aspe
cts,
legi
slat
ion,
etc
Tr
aine
r(s)
A
tten
ded
by
Rôle
Ce
rtifi
cate
of
atte
ndan
ce Y
/N
26
Daily Work Planning
The second category of information is an expanded dataset that can be kept for only a little more effort. This provides additional information valuable in the efficient daily management of both soil and water. The starting point for this information is “day sheets”, which encourage both the daily management and oversight of irrigation and the habit of record keeping. Templates are provided for such short term management information as that listed in the box below:
Daily soil and water management information
• Daily rainfall, accumulated over months and years (multiple sheets)
• Daily record of irrigation amounts applied; according to field areas and crops, and including details of equipment used and timing
• Daily maintenance checks on equipment
• Occasional record keeping of longer-term maintenance of pumps and meters, including any repairs to the system
Also at less frequent intervals, it will be necessary to keep a record of all maintenance and calibration work carried out on the pump station and application equipment.
Additional useful information
Other information such as that listed in the box below may be useful in planning water use on the farm and demonstrating that all possible outcomes of management actions have been considered. There are no templates given for these, but farmers are encouraged to keep their own records as far as they feel competent and happy to do so.
Additional management information
• Farm/field map showing water courses, water disposal and potential risks
• Timing and amount of application are compatible with infiltration rate
• Weather data (daily rainfall and ET) to aid calculation of irrigation need
• Evidence that irrigation scheduling system data inputs are accurate, the system is delivering the required information and that it is cost-effective
For all types of information, at least 6 years of records should be kept, in accordance with the CAMS review cycle, and preferably 12 years (which will be the normal renewal period).
27
Annual rainfall Year:-
Month:- Amount (mm) Month:- Amount (mm)
1 1 2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
21 21
22 22
23 23
24 24
25 25
26 26
27 27
28 28
29 29
30 30
31 31
Monthly total Monthly total
28
Irri
gatio
n w
ater
app
lied
to e
ach
crop
– D
ay s
heet
Dat
e Fi
eld
nam
e/N
o.
Are
a (h
a)
Cro
p Sc
hedu
led
Met
hod
of
Day
or
To
tal a
pplie
d
am
ount
app
lied
appl
icat
ion
nigh
t vo
lum
e*
(m
m)
(tho
usan
d cu
bic
m
etre
s (‘0
00 m
3 ))
*Tot
al V
olum
e =
‘000
m³
(ha
on w
hich
app
lied
x m
m a
pplie
d) ÷
100
29
Mai
nten
ance
che
ck –
Day
she
et
Dat
e Eq
uipm
ent
Che
cked
for/
Act
ion
take
n
App
licat
or c
heck
Dat
e A
pplic
ator
C
heck
ed fo
r/A
ctio
n ta
ken
Oth
er a
ctio
ns
Dat
e A
ctio
n ta
ken
30
Pum
p m
aint
enan
ce
Dat
e Pu
mp
iden
tifica
tion
By
who
m
Prob
lem
iden
tifica
tion
and
Act
ion
take
n
Met
er m
aint
enan
ce
Dat
e M
eter
iden
tifica
tion
By
who
m
Prob
lem
iden
tifica
tion
and
Act
ion
take
n
Und
ergr
ound
mai
ns m
aint
enan
ce e
.g. l
eaks
Dat
e B
y w
hom
A
ctio
n ta
ken
Ove
r-gr
ound
mai
ns m
aint
enan
ce e
.g. l
eaks
Dat
e B
y w
hom
A
ctio
n ta
ken
6 A toolkit for efficient water use
Attached to the inside back cover of this booklet is a CD with two Excel Workbooks. One of these is a simple irrigation scheduler that will enable you to plan and monitor your water use on individual crops (Scheduler.xls), whilst the other is a series of spreadsheets on which you can collect information about irrigation water use on the farm to provide a comprehensive set of records (Irrigation usage.xls). The two workbooks are linked so that accumulated totals of water applied as irrigation from the scheduler are automatically transferred to the correct cells in the Irrigation usage spreadsheet.
A basic knowledge of operating “Excel” will be all that is necessary to use these tools, using the instructions below. A full set of computer records can then be collected over several years to demonstrate efficient water use in the farm’s irrigation plan.
Both workbooks provide only a basic introduction to irrigation scheduling and water use planning, and are designed primarily for those that do not already use a scientific scheduling approach of any kind or keep adequate records of water abstracted and applied. The Scheduler uses a simple “real time” water balance approach, based upon generic regional estimates of daily evapo-transpiration derived from long-term weather records. It is therefore not as accurate as many of the alternatives on the market which measure actual evapo-transpiration (ET) on site, or access such measurements from a local source. If however, local ET measurements are available, then they can be substituted into the tables of the Scheduler for a more site accurate version (see note 6 below). In addition, the Tables do not include sophisticated crop factors, and may not be accurate at low crop cover rates.
The Scheduler should not be used instead of any of the more sophisticated computer programmes and instrumented systems available on the market, which should provide more accurate, site and time specific information.
Operating the Scheduler
The workbook contains eight data sheets. These comprise:
1. Instructions; which outlines how to use the scheduler tool.2. Input codes; which provides a numeric code for lists of crops and locations (county)
and which is read only.3. Daily Crop Input Data – Low AWC; which is one of the three data sheets where data is
inserted every day and irrigation schedule instructions displayed. This one is for soils on the farm that are classified as “Low AWC” (see page 5), and provision is made for five such crop areas.
4. Daily Crop Input Data – Med AWC; is the same as the above except that it is for soils on the farm that are classified as “Medium AWC” (see page 5), and provision is made for five such crop areas.
5. Daily Crop Input Data – High AWC; is the same as the above except that it is for soils on the farm that are classified as “High AWC” (see page 5), and provision is made for five such crop areas.
6. Scheduler Calculations; is the sheet where all the calculations take place and is again read only. Calculations are made in a simple water balance equation that balances regional estimates of daily evaporative demand against operator supplied values of rainfall and irrigation applications.
31
7. ET by county and month; contains the daily potential evapo-transpiration estimates for all the locations (by county) in England and Wales for the six months of interest from April to September (inclusive), and is read only. If actual ET values are obtainable, they can be substituted into these tables.
8. Soil & Crop Tables; contains lists of crops for each soil type (AWC) and the commonly accepted soil moisture deficit (SMD) at which irrigation is usually started (see pages 6&7) and the amount normally applied once this SMD is reached (read only). Again, these values can be modified by more proficient users according to their own requirements.
To operate the scheduler it is expected that daily rainfall readings or estimates will be keyed in by the operator together with any irrigation water applied that day. It is thought that most growers now collect rainfall data on site, but estimates from the Met. Office or web-based sources for the local area can be used. The only other reading or estimate required is the date when 20 % ground cover will be achieved by the crop. It is thought that this should be estimated at establishment, but a closer estimate substituted when the crop nears and achieves 20 %.
General principles of the sheets are that yellow filled boxes require a data input, and grey filled boxes are to hold identifying information.
On opening the spreadsheet a dialog will prompt you to choose one of two options:
1. Use the data entry dialog to enter information. Data entered using this dialog will populate the spreadsheet automatically.
2. Go directly to the spreadsheet and enter the data manually. This is the default option.
Click the OK button to confirm your selection.
Option 1. To use the data entry dialog
A Data entry dialog is displayed.
At the top of the dialog you are asked to enter location information. Select your region from the left hand drop down list. The right hand drop down list will allow you to select your county based on your region selection.
Below the location information a tabbed dialog allows you to enter information based on whether the soils on your farm are classified as Low AWC, Medium AWC or High AWC.
Each tab allows you to enter the following information on up to 5 crop areas:
• Crop area identifier• Crop type – selected from a drop down list • Estimated date in the form (DD/MM/YYYY) when 20% of crop cover is expected
Once all the data have been entered, press OK on the Data entry screen to confirm the data and to close the form. The information entered automatically updates the spreadsheet.
Daily rainfall readings and irrigation applied must be entered on the spreadsheet manually as described in points 9 and 10 below.
32
The data entry screen may be opened at any time by selecting the Enter Data button on any of the three Daily Crop Input Data worksheets.
Option 2. To use the spreadsheet manually proceed through the following steps:
1. Select option 2 on the initial dialog, select OK and you will go directly to the spreadsheet.
2. Look up your location on the Input Codes sheet (2 above) and obtain the numerical code for it from column D.
3. Open one of the “Data Input “ sheets (3-5 above) according to soil type, and key-in the location code at cell B3. The county by text will appear in cells C&D3.
4. Type in an identifier for your crop area in the grey box at the top of a blue column i.e. H3 for Crop area 1.
5. Look up the crop for this field area on the Input Codes sheet (2 above) and obtain the numerical code for it from column A.
6. On the “Data Input “ sheet (3-5 above) key-in the crop code in the yellow box for that field area (e.g. cell G5 for crop area 1). The crop type, and irrigation amount and trigger SMD will appear in adjacent cells (i.e. H – J5).
7. Type in an estimated date (DD/MM/YYYY) when 20% of crop cover is expected in the yellow box below the above information (e.g. H7 for crop area 1). This estimate should be regularly updated as the season progresses, but it is important to insert your best estimate for the correct operation of the scheduler. Once 20% is achieved the actual date should inserted.
8. Once this is done figures will appear in the irrigation application recommendation column (i.e. K), which will change as rainfall and irrigation data are inserted.
9. Insert rainfall on a daily basis into the appropriate column (i.e. G) coloured light blue).10. Also insert any irrigation applied in the adjacent column (i.e. H) coloured mid-blue,
including that applied for non-yield purposes (e.g. to ease emergence of certain crops – see pages 8-10).
11. The scheduler will then calculate the soil moisture deficit (SMD) as it develops day-by-day. When the trigger SMD is reached, a recommended amount will appear as red text in the “apply irrigation “ column (i.e. K).
12. It is assumed, and recommended, that irrigation is applied at night (evapo-transpiration due to both wind and radiation is lower, and the full water application is allowed to penetrate to the root zone more efficiently).
13. Repeat the above procedure for each crop area on each soil type throughout the season. As the season progresses the total amount of rainfall received, and the amount of irrigation water applied, will appear in the light green boxes at the base of their respective columns (i.e. G & H).
14. If the “Irrigation Usage” tool workbook is also open, the accumulated total for irrigation water applied will also appear in the relevant cells of the “Seasonal irrigation water use” spreadsheet (i.e. C6).
Save the open version of “Scheduler”, together with your input and changes, to your own hard drive on your computer. For further use and input, open this version, so that past data is not lost and remember to save all further input and changes throughout the season.
33
Operating the Irrigation Usage tool
Please note that this tool is linked to the Scheduler tool so that data entered in the scheduler will automatically be updated in Irrigation Usage. On opening the workbook a message box is displayed asking if you wish to update this workbook with changes made to the other workbook. Select No to keep existing information and select Yes to link to the Scheduler workbook. If you select Yes a browser dialog box will appear and you can navigate to the location of Scheduler.xls.
Make sure you use the current copy of scheduler on your hard drive if you have already input data
The workbook contains three data sheets. These comprise:
1. Instructions; which outlines how to use the Irrigation Usage tool.2. Basic Farm Information; which collects together all the information on the farm’s
abstraction resources together and generates an overall assessment of how much water is available for irrigation in the coming season.
3. Seasonal Irrigation Water Use; which collects the accumulated irrigation water applied to crop areas recorded on the Scheduler workbook and calculates the total volume applied on the farm during the season.
The general principle of the “Basic farm information” sheet is that yellow filled boxes require identifying information to be filled in, and buff coloured cells require data input (although some are calculated automatically). Grey filled boxes are title and heading information to guide completion of adjacent boxes.
Following the initial message box about linking the workbooks as described above, a dialog will prompt you to choose one of two options:
1. Use the data entry dialog to enter information. Data entered using this dialog will populate the spreadsheet automatically.
2. Go directly to the spreadsheet and enter the data manually. This is the default option.
Click OK to confirm your selection.
Option 1. To use the data entry dialog
A Basic Farm Information dialog is displayed. Data pertaining to the farm may be entered in the white textboxes. Use the Tab key to move from one textbox to the next.
If you wish to enter abstraction licence data click on either the Enter Summer Abstraction Data button or the Enter Winter Abstraction Data button.
E.g. Select the Enter Summer Abstraction Data button. A data entry dialog appears. Enter the information required in the white textboxes.
34
The buttons on the right hand side of the Summer Abstraction dialog allow you to work through the data records. Their functions are explained in the table below:
Button Name Function
New This clears any data in the currently displayed record and allows new data to be entered. Once data have been entered press the Enter button to add them to the list.
Delete Permanently deletes the record
Restore Click Restore before pressing Enter or scrolling to another record to undo changes you made in the data. Clicking Restore will not restore a deleted record.
Find Prev Displays the previous record in a list. If you specified criteria using the Criteria button, Find Prev displays the previous record that matches the criteria.
Find Next Displays the next record in a list. If you specified criteria using the Criteria button, Find Next displays the next record that matches the criteria.
Criteria Finds records based on the criteria you specify.
Close Closes the data entry form. You must save your workbook to save any records added to your list with the data form.
35
The Winter Abstraction data entry form works in the same way as the Summer Abstraction data entry form.
Once all the data have been entered, press OK on the Basic Farm Information data entry screen to confirm the data and to close the form. The information entered automatically updates the spreadsheet.
The Basic Farm Information data entry screen may be opened at any time by selecting the Enter Data button on the Basic Farm Information worksheet.
Option 2. To use the spreadsheet manually proceed through the following steps:
1. Fill in all the yellow boxes on the “Basic farm information spreadsheet” in the workbook.
2. Also fill in Abstraction Licence information for each abstraction point on the farm, for both summer and winter (peak flow) abstraction in the buff cells in sections C21 – G30 and C34 – G43.
3. Complete the buff cells by inserting pump meter readings into columns I and H for the start and end of the abstraction season respectively. The spreadsheet then calculates the total amount abstracted during the season and displays this in column J, and this total expressed as a proportion of that allowed on the Licence, in column K.
4. The accumulated totals at the end of the season are shown for both summer and winter abstraction in the blue cells of rows 31 and 44 respectively, and for the whole farm on row 47.
36
5. If the Scheduler workbook is being used, then information of actual irrigation water use for each crop area is automatically fed into the correct cells for the relevant crop areas on the “Seasonal irrigation water use” spreadsheet.
6. This spreadsheet then automatically calculates the amount applied as a volume of water, both cumulatively during the season, and at the end of the season the total volume used on the farm.
7. The total volume used in a season is also fed back onto the “basic farm information spreadsheet” at cell F50 in the commonly used thousand cubic metre units (000m3). This total is also expressed as m3 in the next cell (G50) and expressed as a proportion of the water available in cell H50 and that licensed for abstraction in K50.
These workbooks can be saved under new titles year upon year to maintain a record of farm irrigation water use efficiency.
Other Defra/ADAS Grower Guides in this series:
Irrigation Best Practice, Water Management for Potatoes, December 2005Irrigation Best Practice, Water Management for Field Vegetable Crops, July 2003 Irrigation Best Practice, Water Management of Soil and Substrate – Grown Crops (Top and Soft Fruit), February 2003Irrigation Best Practice, Container –Grown Ornamentals, March 2002
All available from ADAS, Battlegate Road, Boxworth, Cambridge CB23 4NN Tel: 01954 268214 or email: [email protected]
Other useful booklets:
Save water and money – irrigate efficiently, June 2007. Published by Cranfield University and Natural England.Waterwise on the farm, 2007. Published by the Environment Agency.
Acknowledgement
The assistance of Peter Youngs, Group Manager of the East Suffolk Water Abstractors Group (ESWAG), is gratefully acknowledged, as is the advice and critique from Dr Jerry Knox of Cranfield University.
‘Irrigation – A Water Toolkit for Growers’ was written and produced by ADAS UK Limited with funding from Defra
Principal authors: Don Tiffin, ADAS John King, ADAS Stephen Perkins, ADAS Bill Basford, ADAS Associate
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