Improving irrigation practice for growing vegetables on sandy soils

Rohan Prince and Robert Deyl

BackgroundEfficient irrigation is required to maximise yield, water and nutrient use efficiency and therefore, often profit

An irrigation system is only as efficient as the way it is operated

Many tools are available to help predict the water movement in soil e.g. Dripgame and Wetup (CSIRO or CRC for Sustainable Sugar Production)

Our sandy soil have an average of 95% coarse sand.

Root zones of crops

Crops have an effective root zone where they remove the majority of water and nutrients

This root zone is determined by crop type, soil type and structure, and cultural practice

Pictures courtesy of DAFWA

Water movementWater movement is influenced by soil types, structure, irrigation method and volume and cultural practices

What happens on the surface is not what always happens below the surface

Blue dye test shows you the movement of water through soilZwart, P, 2007. ‘Tracing Irrigation Water with Blue Dye and a Shovel’ Ministry of Agriculture, Food and Rural Affairs. Ontario. http://omafra.gov.on.ca/english/crops/hort/news/hortmatt/2007/20hrt07a3.htmSimonne et al, 2004. ‘How to Conduct an On-farm Dye Test and Use the Results to Improve Drip Irrigation Management in Vegetable Production’. Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences,University of Florida HS980. http://edis.ifas.ufl.edu

Results on sandon the surface

On the soil surface the spread of the dye looked good

0.3 L water applied resulted in 20 cm radius from the dripper

2.0 L applied resulted in30 to 40 cm radius indicated

4.0 L applied resulted in40 to 60 cm radius indicated

But this result was only skin deep

Results on sand below the surface

Depth and spread of dye in 2010-11 trial

  Volume applied (L)

Application rate 0.3 0.5 1 2 4 0.3 0.5 1 2 4

L/hr Spread (cm) Depth (cm)

0.3 12.5 16 20 >20 20-30 14 24 30 30 80

0.5 13 19 24 28 30 25 29 40 63 80

1 15 18 19 20 30 25 29 39 68 80

2 17 20 2320-24

20-25 21 25 38 56 80

4 20 20 24 22 32-20 22 27 38 58 67

Daily water application (mm) = Crop factor x EpanScheduling using evaporation

Crop factor curve for irrigating tomatoes on sand

Weather data from DAFWA remote weather station network

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

Week

Prop

ortio

n of

eva

pora

tion

repl

acem

ent

Date  Air TempDegree C

Relative Humidity

Soil Temp @ 4cm

Solar Radiation

Wind Speed

Total Rain

Total Evap

  Min Max Min Max Min Max tot. kJ avg. km/hr mm mm

17-May 19.4 26.2 54.0 86.2 22.4 36.7 30353 13.8 0.0 8.0

16-May 17.3 25.3 48.4 90.7 20.6 34.9 30097 13.9 0.0 8.3

15-May 17.4 27.2 41.3 82.5 20.9 36.1 31653 14.7 0.0 9.2

14-May 17.2 27.8 34.9 73.0 21.0 35.7 31589 16.9 0.0 9.8

13-May 17.3 29.5 24.0 90.9 21.4 37.0 31743 15.2 0.0 10.3

12-May 17.6 34.3 15.3 81.9 23.4 37.0 27141 12.8 0.0 10.0

11-May 17.0 38.4 10.3 71.2 23.7 39.9 29493 9.0 0.0 11.1

The Vegetable Irrigation Scheduling System (VISS)

Scheduling using evaporation

Weeks after planting

Pro

porti

on o

f Eva

pora

tion

repl

acem

ent

2011-12 tomato demonstration crop irrigation

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 180.0

0.5

1.0

1.5

2.0

2.5

3.0

Rain Good Practice Grower PracticeTarget evaporation replacement Polynomial (Target evaporation replacement)

Tools

Soil moisture monitoringFine tuning, not scheduling

0–15 cm 15–30 cm 40–70 cmDepth

Soi

l Moi

stur

e (%

)

Good Practice Grower Practice

2011-12 Demonstration trial2 weeks after transplant

8 weeks after transplant6 weeks after transplant

4 weeks after transplant

Good Practice scheduled using VISS left of each picture Vs Grower Practice right

Grading and pack out

Nutrient N P K Ca Mg S

Good Practice 598.7 135.2 1081.3 402.6 137.0 235.2Grower Practice 482.4 32.1 386.7 139.9 15.6 20.5

Grading Medium-Lg. Medium No1 Medium Small-Med Large Red Ripe Cocktail Green Waste

Good Practice 16% 24% 15% 6% 4% 4% 3% 4% 16%

Grower Practice 13% 23% 17% 8% 2% 3% 4% 7% 13%

Nutrient applications

2011-2012 Demonstration ResultsGood Practice compared with Grower Practice

Similar yields 108 t/ha compared with 105 t/ha

40% less water applied 983 mm compared with 1651 mm

73% less drainage250 mm compared with 950 mm

Similar plant water use733 mm compared with 701 mm

45% less leaching of nutrients265 kg/ha compared with 477 kg/ha

Thank you

and the funding bodies