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P. Firth Hansa Thitipoca Sumalee Suthipradit R. Wetselaar D.F. Beech 《Soil biology & biochemistry》1973,5(1):41-46
At Chainat, in the central plain of Thailand, where problems of double cropping are being investigated, a growth rate and nitrogen uptake rate for maize of 370 and 3.15 kg/ha/ day respectively were obtained. In one season there was a high positive correlation between maximum nitrogen yield and maize grain yield.When 15N-labelled (NH4)2SO4 nitrogen was applied to maize at 100 kg/ha of N, 49 per cent could be recovered in tops after 12 weeks. After 8 weeks, 23 per cent was in the soil organic N plus roots, and after 12 weeks had decreased to 10 per cent. In the same period, the unaccountedfor fertilizer N had increased from 27 per cent at 8 weeks to 41 per cent at 12 weeks.In a long term rotation experiment involving 18 dry and wet season cropping combinations, a provisional balance sheet after two years indicates (1) that the soil nitrogen status can be maintained with the introduction of high input, dry season upland crops into a cropping system where wet season rice is grown only, (2) that in the absence of nitrogen fertilizer about 40 kg/ha of N is added per season to the soil-plant system under rice, and (3) that mung bean (Phaseolus aureus) fixes between 58 and 107 kg/ha of N per season. 相似文献
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