40. Cassava/legume intercropping with contrasting cassava cultivars. Part II
2.selection criteria for cassava genotypes in intercropping with two contrasting legume crops.
Field Crops Research, 29, 1992, pp. 135-149
In the work reported here, 18 diverse cultivars were used in sole-cropping, and in intercropping with soybean and pigeonpea. The objectives of this work were to determine if selection criteria could be developed using characteristics obtained in sole-cropping, and if these were different for different associated species.
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.
The results of this experiment suggest that for cassava/pigeonpea intercropping, selection can be made in sole-cropping for high tuber yield and also for height which should be at least similar to that of the anticipated associated crop. Because of prolonged competition between the two species, the balance of competitiveness of the component crops can be easily altered by cultural modification. It is therefore important to identify competitiveness of component species using a few cassava cultivars under typical growing conditions for the intercropping before a large-scale selection programme is carried out.
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Latin America, Costa Rica, CIAT, beans, varieties, resistence breeding, green revolution, traditional production systems
PACHICO, D. and A. VAN SCHOONHOVEN
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