improving irrigation practice for growing vegetables on sandy soils rohan prince and robert deyl
TRANSCRIPT
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 Epan
Scheduling 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
port
ion
of E
vapo
ratio
n re
plac
emen
t
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 1081.3 402.6 137.0 235.2
Grower 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