Cassava/legume intercropping with contrasting cassava cultivars. 2. Selection criteria for cassava genotypes in intercropping with two contrasting legume crops

Abstract

An experiment was conducted to determine selection criteria for cassava genotypes for intercropping with legumes using 18 cassava cultivars which are contrasting in canopy size. Two legume crops were used; one a short-statured, quick-maturing soybean, and the other, a tall, late-maturing pigeonpea. They were sown at 37 days after cassava planting in double rows between cassava rows. Intercropped soybean had little adverse effect on crop growth and tuber yield of cassava, and in some cases it enhanced tuber yield of cassava cultivars with small compact canopies. The effect of cassava on soybean yield was least with short-statured, small cassava cultivars as solar radiation available to the soybean was highest. As the canopy development of cassava was hardly affected by soybean in any cultivars, the selection of cassava genotypes can be made in sole-cropping with selection criteria of high tuber yield and narrow canopy width measured at about 90 days after cassava planting. Intercropped pigeonpea had an adverse effect on canopy development and tuber yield of cassava, particularly of short-statured cultivars. Whilst tall cultivars with spreading canopy were least affected by pigeonpea, they reduced seed yield of pigeonpea to a very low level. It was therefore difficult to determine cassava types suitable for this intercropping. When strongly competitive species, such as pigeonpea, are to be intercropped with cassava, selection can be made initially in sole-cropping with selection criteria of high tuber yield and height which is at least similar to that of the associated crop. The results show that ideal cassava cultivars for intercropping depend on competitive ability of associated species. It is suggested that competitiveness of component crops should be identified using a few cassava cultivars under typical growing conditions before selection is carried out.