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Abstract

The objective of this study was to investigate genotypic requirement of cassava for intercropping with both non-aggressive (soybean) and aggressive (pigeonpea) crops under different growing conditions. The information gained was used to give a physiological basis for selection of cassava genotypes for intercropping. Five field experiments were conducted in the three growing seasons in subtropical environment of southeast Queensland. In Experiment 1, 7 cassava cultivars were grown as sole crops as well as intercropped with pigeonpea. Pigeonpea was planted at the same time as the cassava at a plant density of 26.7 plants m-2. Pigeonpea was taller than cassava, its canopy spread rapidly, and it suppressed the growth of all cassava cultivars. A slightly higher yield was obtained in tall cultivars which were able to maintain leaf area and to grow rapidly after the pigeonpea was harvested. In Experiment 2 the same cultivars used in Experiment 1 were intercropped with short statured, early maturing soybean and pigeonpea, which were sown at 35 days after cassava planting and at a low density of 6.7 plants m-2. As the availability of solar radiation was reduced by tall, spreading cassava cultivars, growth of soybean was affected greatly whereas intercropped soybean had little effect on cassava growth. The pigeonpea matured much later than soybean, and the canopy height was similar to that of some cassava cultivars. The growth of only short cultivars were severely affected by intercropped pigeonpea while pigeonpea growth was reduced severely by tall cultivars. In both intercropping with pigeonpea and with soybean, cassava yield of 7 cultivars was correlated with that of the sole cropping. The land equivalent ratio (LER) ranged mostly from 1.15-1.57 in cassava/soybean intercropping whereas it was mostly less than 1.0 in cassava/pigeonpea intercropping.