There is growing concern to promote the use of aerobically fermented liquid fertilizer produced from human waste and sludge to reduce the cost, environmental load, and energy consumption in rice production. We tested the maturity accelerating effects on rice straw and effects as a nitrogen fertilizer by applying liquid fertilizer in 2009 and 2010. The maturity accelerating effects were not significant in terms of dry weight, total nitrogen content (T-N), and nitrogen uptake. When liquid fertilizer, which had an ammonium nitrogen (NH4-N) ratio of approximately 70%, was incorporated into the plow layer of the soil as a basal fertilizer, the nitrogen fertilizer effect and panicle number were equivalent to those for chemical fertilizers. However, when liquid fertilizer with a low NH4-N ratio was applied, the dry weight, T-N, and nitrogen uptake were lowered resulting in reduced panicle number. When applied as a top-dressing on the soil surface, nitrogen uptake decreased because of NH4-N loss through volatilization. This decrease in nitrogen uptake may have reduced spikelet number. Nitrogen uptake slowed under the low NH4-N ratio, and nitrogen nutrition conditions deteriorated during the ripening period. This may have lowered 1000-grain weight under the high average temperature conditions in 2010 (26.7°C during the 20-d period after heading). The yield tended to be low because of these reductions in yield components. Nitrogen fertilizer effects were affected by NH4-N ratio, whose fluctuation is considered problematic.
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