Abstract
The effects of preceding crops, maize fodder (Zea mays), mungbean (Vigna radiata), green manure (Sesbania cannabina), farmyard manure (FYM) and fallow, on the response of wet season rice (Oryza sativa L.) to fertilizer N (0 to 150 kg N ha-1) and their residual effects on the succeeding maize crop were investigated on an Andaqueptic Haplaquoll in the Philippines in 1984 and 11985. Mean rice grain yield without fertilizer N was maximum (4.5 t ha-1) after Sesbania and minimum (2.7 t ha-) after maize fodder. Mean yields of unfertilized rice after FYM, fallow, and mungbean were intermediate, decreasing in that order. Yields of unfertilized rice grown after Sesbania, the aboveground biomass of which accumulated 70 kg N ha-1 (1984) and 98 kg ha-1 (1985) in 60 days were comparable with rice yields in fallow plots to which 44 and 96 kg ha-1 fertilizer N, respectively, were applied. FYM (15 t ha-1) supplied 68 kg N. The efficiency of N from FYM in combination with different N levels on rice ranged 31-51 %. Significant residual effects of FYM and green manure on the succeeding maize crop were not detected. However, soil organic C and total N after wet season rice in 1985 were higher when Sesbania and FYM preceded rice compared with maize fodder, mungbean or fallow.
