35. Screening of different tropical legumes in monoculture and in association with cassava for adaption to acid infertile and high al-content soil.
Beitr_ge trop. Landw. Vet. med., 28, 3, 1990, pp. 283-289
In this study 9 tropical grain legumes with 165 cultivars were screened or adaption to a low pH (3.9-4.1) and a high Al content in mococulture and in association with cassava.
In the monoculture experiment, the following grain legumes were tested: mung beans (Vigna radiata), cowpeas (Vigna unguiculata), pigeonpeas (Cajanus cajan), jackbeans (Canavalia ensiformis) as non-climbing, and winged beans (Psophocarpus tetragonolobus) and sword bean (Canavalia gladiata) as climbing species. The plot consisted of a double row 3.75 m in length, with a distance between rows of 0.6 m, and within rows 0.19 m.
In the mixed cropping experiments, the climbers winged bean and velvet bean were not tested, while soybeans (Glycine max) and non-climbing lima beans (Phaseolus lunatus) were added. The grain legume collection was planted in association with cassava (cv.CMC 84). 9 cassava plants were planted with one row of legumes on both sides. The fertility level of the plots was extremely low, only 500 kg/ha of lime was applied. The pH of the soil was even lower than in the monoculture screening experiment.
Good results have been obtained in multiple range cropping of cassava and common beans (Phaseolus vulgaris), but other tropical legumes, especially cowpea (Vigna unguiculata), are needed in cassava intercropping systems for climatic and soil conditions, under which beans do not grow well. This is the case on soils with low pH, low fertility, and high Al and/or Mn content, which are widely distributed in the tropics. An example of these conditions is the soil of the CIAT experimental station Quilichao in Colombia.
On this soil, common beans only grow when high levels of lime and fertilizer are supplied. Other legumes with tolerance of high levels of Al and Mn and low fertility show vigorous growth and high yield even at a very low level of purchased input. Although lower in nutritive value than common beans, their protein contents make them valuable complements to the high calorie producer cassava.
In this study with little or no fertilization the yields were low. The only acceptable yield was obtained from cowpea (Vigna unguiculata), averaging 1.1 t/ha in monoculture and 0,45t/ha in association with cassava. In the latter case, the cassava yield decreased by 26%. The other legumes - except for the velvet bean (Stizilobium derringianum) - were low yielding or without any yield, but some of them increased the tuber and starch yield of cassava.
It may be concluded that in selecting grain legumes for association with cassava, it is relatively safe to do this selection in legume-monoculture screening trials as a first step to eliminate materials with a low potential. Particularly on acid, infertile soils, the overriding factor will be that of adaption to adverse soil conditions; growth will be somewhat reduced and growth habits and therefore competition with cassava will not be serious. Nevertheless, legumes with intense early flowering (and maturity) appear to be most suitable, since early flowering reduces excessive vegetative development unfavourable for cassava yield formation, and early pod filling enables the legume to escape serious shading by cassava.
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Asia, India, study, field trial, intercropping, peanut, pigeonpea, sunflower, finger millet, irrigation, planting geometrics, yield
SANKARAN, V.M. and G. KUPPUSWAMY
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