Nitrogen contributed by grain legumes to rice grown in rotation on the Cununurra soils of the Ord Irrigation Area, Western Australia
1987
Chapman, A.L. (Commonwealth Scientific and Industrial Research Organization, Winnellie (Australia). Div. of Tropical Crops and Pastures) | Myers, R.J.K. (Commonwealth Scientific and Industrial Research Organization, St Lucia (Australia). Cunningham Lab.)
The uptake of N by dry season rice was studied for 3 cropping cycles over 4 years. Dry season rice was drill-sown with or without 100 kg per ha of N applied as urea at permanent flooding. Soybean, green gram and Sesbania crops accumulated 290-360, 80-130 and 110-180 kg N per ha, respectively, in the tops at maturity. An average of about 40 kg N per ha was present in the stem bases and roots. Estimates of nitrogen fixation ranged from 65-72 percent of total plant N when the legumes were grown after 12 months fallow, to 93-95 percent when they were grown immediately following dry season rice. Rice grain yields and N uptake at maturity were generally highest after Sesbania and lowest after a wet season cereal crop. Differences among treatments were small and related to the quantity of N returned in residues. On average, 11 percent of the N in the residues was recovered in the tops of the following rice crop. Rice yields increased over the 4-year period, but mean increases were similar for legume and non-legume treatments.
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