Soil improvement values of legumes in rice-based cropping system
1997
Charintorn Dajdamrongpreecha
Long term study on effects of chemical fertilizers and crop biomass incorporation into the soil in three patterns of sequential cropping systems namely: wet season rice-dry season rice-wet season rice-dry season rice-wet season rice; wet season rice-peanut-wet season rice-peanut-wet season rice and; wet season rice-Sesbania rostrata-wet season rice-Sesbania rostrata-wet season rice were conducted in the farmer's field (sandy loam, Roi-et soil series), Yasothon province during the year 1993-1995. Main factors laid out in the main plots consisted of 3 cropping systems as mentioned above. Sub-sub plots laid out for the third through the fifth crops were factors i.e. 1) control 2) fertilizer application 3) incorporation of crop biomass into the soil and 4) 2+3. Rice peanut and Sesbania significantly responses to chemical fertilizers and trended to response to plant residue incorporated as well. Generally, the best treatment for all crops was to apply chemical fertilizers in combination with crop biomass turnover into the soil. Wet season rice grown in rotating with peanut gave the highest rice yield followed by rice and Sesbania rotation and sole rice systems respectively. Additions of fertilizer grade 16-16-8 for rice increased the soil acidity whereas application of fertilizer grade 9-24-24 and gypsum for peanut and rock phosphate (0-4-0) for Sesbania decreased the soil acidity. Organic matter content in the soil, total nitrogen and available phosphorus were increased as a result of fertilizer application and/or incorporation of crop biomass particularly in the rice/peanut cropping system. Crop residue plowed down only exerted insignificant impact on either soil pH or available potassium content in the soil. In the long run, the properties of this poor fertile sandy loam soil could be improved substantially through successive application and accumulation of chemical fertilizers and crop residues turnover particulary peanut in the rice/peanut cropping system.
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