The study of the world rice protein: Performance fertilizer for paddy Iruka (1963) found: high doses of nitrogen fertilizer, the highest performance at tillering fertilizer, then declines, with dose low quality rice, apply at flowering 10 days before calving and high efficiency (Suichi Yosida, 1985) [117]. According Schunutz and Hartman, 1994 in Germany, if halve fertilizer in cultivation, the crop yield will be reduced by 22% in a short time; 25-30% in the long term, farm income dropped 12%, the profitability of farms fell by 40%, total crop output fell 10% [113], [80]. Findings of Sinclair (1989) [110] also pointed out that fertilizer performance for very different rice, 1kg N for from 3.1 to 23 kg of rice.
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