Effects of irrigation and soil management for fodder crops on root zone conditions in a red-brown earth

Abstract

The irrigated red-brown earths in northern Victoria have traditionally been considered unsuitable for intensive cropping owing to unstable soil structure. This experiment was established to determine whether management systems for continuous double cropping or crop/lucerne rotations could be developed for these soils. A range of tillage levels, flood or furrow irrigation treatments and organic matter additions were imposed in December 1981. Soil strength, measured with a field penetrometer, has been significantly reduced by both surface soil management and deep ripping. The stability of surface soil aggregates has been significantly increased by reducing tillage, by avoiding the rapid wetting associated with flood irrigation and by the addition of organic matter. However, there has been no increase in rooting depth or activity of maize crops, as indicated by soil water extraction patterns and midday leaf water potential data, in response to the treatments imposed. However, lucerne rapidly developed an active root system, deeper in the profile than maize. This deeper root system increased the soil water supply for lucerne by approximately 50 mm.