Studies on the integrated management of fertilizer N and organic manures in cropping sequences; 1: evaluation of green manures [Philippines]
1986
Meelu, O.P. | Furoc, R.E. | Dizon, M.A.
Sesbania gave mean maximum green (dry) matter production of 24.0 (3.4) to 38.8 (9.0) t/ha and indigo minimum of 1.9 (0.2) to 14.5 (3.2) t/ha at 30 DE [days after emergence] and 60 DE respectively. Corresponding mean N accumulations were 84 to 199 kg/ha from Sesbania and 8 to 84 kg/ha from indigo. Other green manures were intermediate to these values. Mungbean and cowpea also gave 0.9 t and 1.4 (0.4) t/ha grain and green (dry) pods, respectively, in 1984. N fixation in terms of ARA [acetylene reduction activity], nodule number and weight also indicated superiority of Sesbania over the green manures. Rice responded significantly to inorganic fertilizer N up to 50 kg/ha in 1984 and 105 kg/ha in 1985. Irrespective of green manure species, rice grain yield of 4.0 t/ha in 1984 and 4.6 t/ha in 1985 without N application was comparable to 4.1 t/ha and 4.7 t/ha with 50 kg and 105 kg N/ha application in weedy fallow, respectively, indicating a substitution of 50 to 105 kg N/ha with green manuring. Sesbania and Crotalaria accumulated more in 60 days than required by the rice crop, suggesting a need to determine optimum crop growth stage and inorganic fertilizer N combinations for rice. Although no significant residual effects from green manures on the succeeding DS rice were detected in 1984, OC and total N content of soil after the 1985 WS rice were significantly more in Sesbania and Crotalaria treatments compared to fertilizer N and other green manure treatments. This was reflected in a significant residual effect on DS rice yield in 1985 from the Sesbania and Crotalaria green manure treatments
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