Pattern of infiltration with furrow irrigation and evapotranspiration of kenaf (Hibiscus cannabinus) grown on Cununurra clay in the Ord Irrigation Area

Abstract

The infiltration characteristics of Cununurra clay, the dominant soil in the Ord Irrigation Area, were examined in a furrow-irrigated experiment with kenaf. The irrigation treatments, which were scheduled on leaf water potentials at dawn and solar noon, ensured that water was applied over a wide range of soil moistures. Flowmeters were used in the supply and drainage channels, and the difference between the flows in these meters was taken as the amount of water infiltrating the soil. The efficiencies of application ranged from 50 to 85% and were inversely related to the frequency of application because the infiltration rate on this heavy swelling soil declined with increasing soil moisture content. Crop water use patterns of kenaf in this semi-arid tropical environment were also determined. Evapotranspiration was estimated from the changes over time in soil moisture in the profile. Clear patterns were established for the changes in the ratio of evapotranspiration to free water evaporation with growth under soil moisture regimes ranging from almost stress-free to severely stressed. A peak value of 1.52 was recorded for the period 14-1 6 weeks after sowing in the most frequently watered treatment.