Contribution of three leguminous species (Mucunapruriens var. utilis, Vigna unguiculata Walp. L and Arachis hypogaea L) to soil productivity

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The contribution of three leguminous crop species Muciinaprtiriens var. utilis, VIgnci unguicu/ala Waip. L and Arachis hypogaea. L ) to soil productivity was investigated from 1995 to 1997 on two Ghanaian soils: Ejura (Lixisol) and Asuansi (Acrisol) series. The legumes were planted in the minor cropping season. Two stubble management practices were imposed (incorporation and surface applied ) on the legume stubble during the major season and two fertilizer levels (0 and 45 kg N, 9 kg P and 19 kg K ha-1 were applied to the test crop (maize). The control treatment consisted of maize following maize with the recommended rate of 90 kg N, 37 kg P and 37 kg K ha-1. Application of half the recommended rate of fertilizer to maize planted after the legumes increased leaf area index, total shoot dry weight, nutrient concentration of ear leaf at silking and grain yield. The legumes did not statistically influence the bulk density of the soils. However, the percent soil moisture content increased as a result of legume/maize rotation. Incorporation of the legume stubble increased the nutrient concentration of the ear leaf and total bacteria population in the soil but did not increase grain yield. There was an interaction between legumes and fertilizer. Application of half the recommended rate of fertilizer to maize following each of the above legumes resulted in a higher grain yield than the control. Maize grain yield was consistently higher when grown after the Mucuna spp. than cowpea or groundnut. The results suggest that for efficient utilization of resources, legumes could be rotated with maize with half the recommended rate of fertilizer rather than continuous maize with higher rates of fertilizer application. Such a system will cut down cost on fertilizer and improve grain yield of farmers.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy in Agronomy, 1999