Rice yields as influenced by Azolla N2 fixation and urea N-fertilization |
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Authors: | A. B. Manna P. K. Singh |
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Affiliation: | (1) Laboratory of Blue-green Algae and Azolla, Central Rice Research Institute, 753006 Cuttack, Orissa, India |
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Abstract: | Application of 0, 30, 60, 90 and 120 kg N ha–1 of urea (U) in split doses with (and without)Azolla pinnata, R. Brown was studied for three consecutive seasons under planted field condition. Fresh weight (FW), acetylene reduction activity (ARA) and N yield of Azolla were found to be maximum 14 days after inoculation (DAI). Among the different treatments, maximum Azolla growth was recorded in no N control. The FW, ARA and N yield of Azolla were inhibited increasingly with the increase in N levels. Irrespective of season, FW and N yield of Azolla were inhibited only a small extent with 90 kg N ha–1 U, beyond which the inhibition was pronounced. ARA was inhibited only slightly up to 60 kg N ha–1 of U. Grain yield and crop N uptake of rice increased significantly up to 90 kg N ha–1 of U (alone or in combination with Azolla) in the dry seasons (variety IR 36) and up to 60 kg N ha–1 U in the wet season (variety CR 1018). |
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Keywords: | Azolla pinnata Nitrogen fixation N yield Oryza sativa Urea-N |
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