1

Scandinavian projects

with deficit irrigation

ETS Field Days, Copenhagen 2015

Trygve S. Aamlid

NIBIO Turfgrass Research Group

Three principally different irrigation strategies

-40

-30

-20

-10

0

0 2 4 6 8 10 12 14

Day number

mm

de

fici

t

Frequent to field capacity Deficit Infrequent to field capacity

2

The DEFICIT kan be calculated in

different ways:

1. Based on water balance, i.e. difference

between Rainfall and Evapotranspiration

Reference ET (ET0) is calculated from a weather

station giving information about:

- irrradiance - temperature

- rel. humidity - wind speed

The deficit is expressed as

- 50 / 60 / 70 / 80 % ET replacement

2. Direct measurement of soil water content using a TDR instrument

Deficit irrigation: Irrigation only to a

certain percentage of FIELD CAPACITY

This method is more

convenient

(at least on greens !)

3

In order to be able to calculate the SOIL

WATER DEFICIT, we need to know the soil

water content at FIELD CAPACITY• Take a cylinder sample to root depth

using a soil corer (e.g. cup cutter) of

known diameter and as deep as there are

visible roots. Volume = 𝝅 𝒓𝟐 𝒙 𝒉

• If the main time of irrigation is in the early

morning, the sample should be taken one

hour after heavy rainfall or redundant

irrigation (to saturation)

• Core weight is determined before and

after drying at 100 C for 24 hours.

• FC (%) = 100 x Weight loss / core volume

(To be verified with the TDR instrument)

STERF PROJECTS WITH DEFICIT IRRIGATION ON

GOLF GREENS

Trials under mobile rain-out shelter, NIBIO Landvik

• 2010-2011: Creeping bentgrass ‘Independence’

• 2013-2015: Red fescue (blend of four varieties)

• USGA spec green. Constructed 2007

• 10 vol % peat in root zone: Ignition loss: 0.9 %

• Soil water content at FC: 20 vol%

4

The entire experimental area was

treated with the soil surfactant

Revolution in spring 2014

IRRIGATION OF EXPERIMENTALPLOTS 2013-2015

EXPERIMENTAL PLAN,

CREEPING BENTGRASS 2010-2011

Factor 1: irrigation (main plot)

1. Irrigation to FC 6x per week (all days except Sunday)

2. Irrigation to FC 2 x per week (Mondays and Fridays)

3. Irrigation to FC 1 x per week (Mondays)

4. Deficit irrigation 6 x per week (all days except Sunday)

5. Deficit irrigation 2 x per week (Mondays and Fridays)

6. Deficit irrigation 1 x per week (Mondays)

Factor 2: Soil surfactant (subplots)

A. No surfactant

B. Revolution, 19 L/ha before the start of the trial

followed by 9.5 L/ha every second week

5

0.0

0.5

1.0

1.5

2.0

2.5

1 2 3 4 5 6 7 8 9 10 11 12

Cro

p c

oef

fcie

nt,

Kc

Days after starting dry-down cycle

IRRIGATION TREATMENTS

1 2 3

4 5

6

Aamlid, Knox, Riley,

Kvalbein, Pettersen,

J. Agr. Crop Sci. 2015

It soon became apparent that deficit irrigation onlyonce a week was not acceptable in creeping bentgrass

6

Plots with deep

and infrequent

irrigation to FC

once a week also

developed

localized dry

spots if they

were not treated

with the soil

surfactant

Revolution

No surfactant

4

6

8

10

12

14

16

18 FC 6xper wkFC 2xper wkFC 1xper wkDef. 6xper wkDef. 2xper wkDef. 1xper wk

Soil water content during the trial period, 2011 (TDR measurements)

7

Relationship between soil water content

and development of dry spots

0102030405060708090

0 2 4 6 8 10 12 14 16Dry

sp

ots

, % o

f p

lot

are

a o

n

5 A

ug.

, aft

er

war

m p

eri

od

Soil water content in top 12 cm, mean of observations 29 July - 5 Aug.

Inte vätmedel

RevolutionRevolution

No surfactant

Main effect

irrigation

Total

water

use,

mm

Visual

turf

quality

(1-9)

Dry

spots, %

of plot

area

Ball roll ,

cm (short

stimpmeter)

Surfacehardness(Clegg-

Hammer, 2.25 kg)

1. FC, 6x per wk 358 6.4 6 100 71

2. FC, 2x per wk 238 6.1 6 102 74

3. FC, 1x per wk 173 5.5 13 100 79

4. Deficit., 6x per wk 123 6.4 8 101 76

5. Deficit, 2x per wk 127 5.9 11 100 75

6. Deficit, 1x per wk 106 4.9 27 103 85

Sign. (*) (*) ns **

Main effect surfactant

A. No surfactant - 5.7 21 102 77

B. Revolution - 6.1 4 100 76

Summary of results, creeping bentgrass

20 June – 22 Aug. 2011

8

Revolution

No surfactantNo surfactant

Revolution

By end of trial, 22 Aug. 2011

Revolution

No surfactant No surfactant

Revolution

By end of trial, late Aug. 2011

9

SUMMARY, CREEPING BENTGRASS

1. Light and frequent deficit irrigation gave: • Lowest water consumption with frequent deficit irrigation

(66 % less than frequent irrigation to FC)

• The same visual turf quality as irrigation to FC

• Less localized dry spots than deep and infrequent irrigation to FC

• The same root weight but not as deep roots as deep and infrequent

irrigation to FC.

2. The soil surfactant Revolution did not increase the overall water

content of the top layer, but the spatial distribution became

more uniform.

3. The water content on creeping bentgrass greens should not be

allowed under 8%, especially if the turf is not treated with a soil

surfactant.

In 2012, the trial area was converted to red fescue

(+ an intentional contamination with Poa annua)

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Split-plot plan for experiment under rainout-

shelter, Landvik, 12 Aug. 2013 – 10 Aug. 2015

Factor 1: Irrigation (main plots)

1. No drought stress. Irrigation to field capacity ( 20 vol% water) 3x per week (FC3)

2. Deficit irrigation to 60 % of field capacity (12 vol% water) 3x per week (DEF3)

3. Deep and infrequent irrigation to field capacity, 1x per week (FC1)

4. a) As treatm.2 but with irrigation to FC every 2 wk (DEF-FC) (Aug.13-Aug.14)b) Deficit irrigation to 60 % of FC 1x per week (DEF1) (Aug. 14-Aug.15)

Factor 2: Fertilizer distribution (subplots)

a. Late spring+

b. Flat rate

c. Early autumn+

Experimental year 1: 12 Aug. 2013 - 11 Aug. 2014

Experimental year 2: 11 Aug. 2014 - 10 Aug. 2015

Soil water content

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MAIN EFFECT OF IRRIGATION TREATMENTS,

AUG 2014- AUG. 2015Visual quality

(1-9)

Poaannua, %

of plot area1

Moss, % ofplot area

Surfacehard-ness1

Dailyheightgrowth

mm

1. To FC 3x per week 5.5 a 14.4 a 4.7 a 83 a 0.73

2. Deficit to 60 % of FC 3x per week 5.2 b 11.5 ab 1.3 a 88 b 0.62

3. To FC 1x per week 5.2 b 11.6 ab 0.3 a 90 c 0.52

4. Deficit to 60 % of FC 1x per week 4.9 c 9.7 b 0.1 a 92 d 0.35

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DEFICIT

IRRRIGATION

22

Wettest and dryest treatments by theend of the trial, 11 Aug. 2015

Irrigation to FC

3x per week

Deficit

irrigation 1x

per week

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SUMMARY, RED FESCUE GREENS

1. Deficit irrigation to 60 % of FC 3x per week gave 69 % less water consumption than irrigation to FC 3x per week and 44 % less water usethan deep and infrequent irrigation to FC 1x per week

2. The visual turf quality and Poa annua contamination was the same withdeficit irrigation 3x per week and with irrigation to FC 1x per week, butirrigation to FC 1x per week tended to result in firmer greens and less moss.

3. Red fesuce did not develop as distinct dry patches in the same way as in former trials with creeping bentgrass, but in the last experimental year, soil water contents down to 4 % resulted in large areas with light colorand less growth.

4. The critical soil water content will probably vary from green to green, butin our case, a TDR values of 6 % was not critical for red fescue if the green had been treated with a soil surfactant.

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