Nitrogen fixation in groundnut and some other grain and green manuring legumes and their residual N Benefits to succeeding rice
1997
Banyong Toomsan | Viriya Limpinuntana | Juckrit Homchan (Khon Kaen Univ. (Thailand). Faculty of Agriculture. Dept. of Agronomy)
Groundnut variety (MGS9xChico)-12-16-5 gave the highest dry matter (6060 kg/ha) and economic yields (1910 kg/ha) comparing to other legumes. It also fixed more nitrogen than other legumes (102 kg N/ha). Sesbania rostrata intercropped with multipurpose cowpea fixed almost the same amount of nitrogen (97 kg N/ha). Multipurpose cowpea (MCP), stakeless yard-long bean (SYLB), Sesbania rostrata (SR), Aeschynomene afraspera (AA), and AA+MCP fixed 63, 62, 64, 59 and 61 kg N/ha, respectively. All the legumes except for stakeless yard-long-bean and non-nod groundnut gave positive net benefits from fixation when stover was returned to the soil ranging from 7 kg N/in the case of multipurpose cowpea to 64 kg N/ha in the case of Sesbania rostrata. Groundnut contributed 33 kg N/ha to the system which was higher than the other grain legumes. Rice growth and nitrogen content corresponded very well with the net benefit from fixation of each N2 fixing legume i.e. being highest in rice grown after Sesbania rostrata and lowest in that grown after stakeless yard-long bean. Rice grown in fallow plot that received 60 kg N/ha as urea and P and K fertilizers gave the highest growth, yield and nitrogen content. This indicated that the N in the added stover did not meet the demand of the rice plant. The 15N labelled stover study indicated that 2-18 kg N in the succeeding rice originated from the added stover, depending on the types of the stover. This accounted for 6-36 percent of the total rice N or 9-22 percent of total N in added stover. Groundnut contributed 8 kg N/ha to the succeeding rice (19 percent of total rice N or 9 percent of the added stover).
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