Section 8
Chapter 7,930

The relative roles of nitrogen fixation fertilizer crop residues and soil in supplying nitrogen in multiple cropping systems in a humid tropical upland cropping system

Sisworo, W.H.; Mitrosuhardjo, M.M.; Rasjid, H.; Myers, R.J.K.

Plant and Soil 121(1): 73-82


ISSN/ISBN: 0032-079X
Accession: 007929460

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This work provides information relevant to the nitrogen (N) management strategy of multiple cropping in upland systems in the humid tropics of the transmigration areas of Sumatra, Indonesia. The experiment was concluded on a red yellow podzolic (orthoxic palehumult) soil at Kota Bumi in Lampung Province, Indonesia, where the annual rainfall of 2430 mm allows three consecutive crops per year to be grown. Two sequential systems were studied.sbd.rice-soybean-cowpea and rice-crop-cowpea. For each crop, crop residues and fertilizer applied to subplots were labelled with 15N so that the crop N uptake for the planted crop and subsequent crops could be partitioned into that derived from N fixation (legume only), fertilizer, crop residues and soil. The experiment was conducted over two years (6 crops). The percentage of soybean and cowpea N derived from N fixation was 33% for soybean and 12-33% for cowpea. Removal of N in seed exceeded the amount derived from fixation. Efficiency of utilization of fertilizer N ranged from 9-18% of that applied for wet season upland rice (900-1300 mm rainfall) to 32-40% for dry season corn (410-840 mm rainfall). Residual fertilizer N recovery by subsequent crops was as high as 14% of that applied to corn and as low as 2% of that applied to rice. Legume residues were an effective source of N to the following crop, particularly cowpea residues applied to rice, where percent recovery was higher than from fertilizer. Cereal residues were of lower value as a source of N. Percent utilization of N in crop residues by the following crop was related to the % N in the residue and the rainfall received by the following crop (R2 = 0.69, P = 0.01).

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