Green manuring and nitrogen fertilization effects on soil chemical properties, agronomic traits and grain yield of upland rice

Abstract

A field experiment was conducted at the University of Agriculture, Abeokuta (UNAAB), Nigeria to screen three green manure crops in the 1997 cropping season for biomass production. The most promising legume was selected, grown and incorporated insitu along with varying levels of inorganic nitrogen fertilizer. The effects of these treatments on agronomic trait and yield of upland rice and soil chemical properties were then investigated at UNAAB and Olowo-Papa village (OP). In the first experiment three green manure crops, namely, Mucuna utilis, Canavalia ensiformis and Lablab purpureus were screened for biomass production in a Randomized Complete Block Design with three replicates. The biomass of M. utilis (25.5 t/ha) was significantly higher than those of C. ensiformis (20.4 t/ha) and L. Purpureus (2.1 t/ha). The second experiment was laid out in a split- plot design at the two sites. Mucuna, which produced the highest biomass in the first experiment, was chosen as the green manure crop. The main plot was green manure (no green manure and green manure) and N-fertilizer constituted the subplot treatment (0, 30, 60 and 90 kg N/ha). The results showed that rice plants grown on green manure plot had higher panicles/m2, number of grains/panicle and grain yield than in the control plot. The contribution of green manure incorporation to grain yield was estimated to be 56%. The plot treated with 90 kg N/ha had the highest rice yield at OP. It was found that the response of rice to N fertilizer application depended on green manuring. Mucuna grown with the late rains as pre-rice green manure has the potential of increasing the grain yield of the subsequent rice crop. Keywords : Canavalia ensiformis ; inorganic fertilization; Lablab purpureus; Mucuna utili Moor Journal of Agricultural Research Vol. 7 (1&2) 2006 pp. 1-8