Modification by crop rotations of the nitrogen fertiliser requirements for irrigated cotton and soil test calibration

Abstract

Benefits of rotational cropping were investigated in the Emerald Irrigation Area, central Queensland. A site cropped with cotton (Gossypium hirsutum L.) in 1983-84 was subdivided into areas left fallow or nitrogen fertilised and sown with wheat. In November 1984 each area was subdivided for five cropping treatments, fallow, dryland soybean (Glycine max.) with nil and 180 kg N/ha, and cotton (Deltapine 61) with 60 and 180 kg N/ha. Subsequently, in November 1985, each plot was sown with cotton (Deltapine 90) receiving 25 or 175 kg N/ha. Soil was sampled in April and October 1984 and in August 1985.