26. Agronomic modification of competition between cassava and pigeonpea in intercropping.
Field Crops Res., 30, 1992, pp. 131-146
The objective of the study was to gain better understanding of how competitiveness of component species in cassava intercropping is determined and modified by agronomic practice when a long-season crop (pigeonpea) is used in association. Two cassava cultivars of contrasting canopy size were used, in addition to the variation in time of sowing and plant density of pigeonpea, to vary further the competitive ability of cassava.
In all intercropping treatments, radiation interception by the combined canopy increased rapidly, and full ground was maintained up to pigeonpea harvest (ca. 100 days). When pigeonpea was planted simultaneously with cassava, it became taller than cassava and its canopy occupied most of the cassava interrow space. When it was sown 35 days later than cassava, then cassava cultivar MCol 1468, which was tall and had a large canopy, dominated pigeonpea almost completely, whereas the smaller cultivar M 19 occupied up to only about half the total interrow area. Pigeonpea at high plant density (based on four rows between cassava rows) had similar height to that at low density (based on two rows), but its canopy occupied more interrow space and enhanced its competitiveness. The canopy width during the time of the complete ground cover was directly related to total dry-matter production and partial land equivalent ratio (LER) for economic yield of each component crop. However, cassava LER was more sensitive to reduced cassava canopy width than was pigeonpea LER, and higher total LER was obtained when a large cassava canopy width was maintained.
The results suggest that when cassava is intercropped with a crop of high competitiveness, agronomic management should be adopted so that the cassava canopy is taller than or about the same height as the associated crop and it occupies most interrow space.
The results also suggest that for high total LER of economic yield, the cassava/pigeonpea intercrop should be managed so that a wide cassava canopy is maintained when the ground is fully covered. This is because cassava LER is more sensitive to reduction in its canopy width than is pigeonpea LER. It appears that when pigeonpea dominates and cassava canopy widths is reduced, tuber growth is reduced.
It is therefore concluded that a vigorous cassava cultivar and late sowing of pigeonpea at a low density can sustain the desirable canopy width and competitiveness for high productivity of cassava/pigeonpea intercropping.
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Africa, Nigeria, savanna, study, white Guinea yam, minisetts, production systems, economic evaluation
KALU, B.A. and P.O. ERHABOR
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