Page 3 water use was increased in the deep tilled plots (Table 3). The data demonstrate that the big effect of the deep tillage (30cm) treatment was to increase crop transpiration at the expense of bare soil evaporation, increasing water use efficiency by reducing unproductive water loss. Table 3. Seasonal crop water use and estimates of crop transpiration (T) and bare soil evaporation (Es) and water use efficiency in the Ouyen trial. All values are mm of water. Statistically significant differences between treatments within years are in total water use are indicated.
Year
Treatment
Water use (mm) 144a 139a 145a 157b 157b 144 139 145 157 157 107a 111ab 115ab 118bc 126c
2017 Barley
Control Pre-drill to 20cm -once Pre-drill to 20cm -annual Deep till to 30cm -once Deep till to 30cm - annual 2018 Wheat Control Pre-drill to 20cm -once Pre-drill to 20cm -annual Deep till to 30cm -once Deep till to 30cm - annual 2019 Barley Control Pre-drill to 20cm -once Pre-drill to 20cm -annual Deep till to 30cm -once Deep till to 30cm - annual
T (mm)
Es (mm)
79 91 86 129 117 55 56 59 66 82 71 82 92 91 110
65 48 59 28 40 89 83 86 91 75 36 29 23 27 16
To highlight this we have plotted the water use efficiencies of the control and deep tillage (30cm) treatments for 2017 in Figure 1 in the “French & Schultz” format, using the bare soil evaporation (Es) values from Table 3 as the X axis intercept terms and the slope calculated as grain yield/transpiration, with the transpiration (T) term coming from Table 3 also. This figure shows that the water use efficiency is improved by moving the line to the left in the deep tilled (30cm) treatment, which shifts the WUE line upwards (more yield) for the same amount of total water used. We also note that the slope of the line is slightly less in the deep tilled (30cm) treatment.
4.0
Grain yield (t/ha)
3.5
Deep tilled (30cm)
3.0 2.5 2.0 1.5
Control
1.0
0.5 0.0 0
50
100
Water use (mm)
150
200