Azolla and Sesbania as biofertilizers for lowland rice
1987
Ventura, W. | Mascarinas, G.B. | Furoc, R.E. | Watanabe, I. (International Rice Research Inst., Los Banos, Laguna (Philippines). Soil Microbiology Dept.)
Azolla and Sesbania have high protein as green manures for lowland rice because they can grow in flooded soil conditions and they fix large amount of N2. Field experiment was conducted to evaluate their biofertilizer efficiency for lowland rice. Both Azolla microphylla and Sesbania rostrata were grown before transplanting rice and azolla was additionally grown with rice at early growth stage. Confirmatory tests were conducted in concrete plots and in metal squares with 15N labelled azolla and urea to determine the pattern of nitrogen availability from the green manure. Results of the study of three cropping seasons showed that sesbania and azolla significantly improved rice yield and have the capability of supplying all the fertilizer N requirement of a rice crop. Recovery of applied N was higher from these two green manures than from urea fertilizer. When incorporated into the puddled soil, azolla and sesbania had gradual N release, that 70% of their N content became available within 20 days, suitable to meet the needs of the price plant. The value of azolla and sesbania as biofertilizers depend on their growth and biological N2 fixing abilities. Factors affecting their growth and practices to improve their biofertilizer values are discussed.
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