Abstract:

【Objective】Field experiments were carried out to study the optimum substitution of partial mineral-fertilizer- nitrogen (N) by organic-fertilizer-N and to provide a base for the commercial development of mixed organic and mineral fertilizers for rice. 【Method】 Field experiments were done in Changshu city, Jiangsu province under different substitution rates and four N fertilizer rates. 【Result】 Grain yields of 8 242-10 187 kg?hm-2 (4007) and 10 048-11 654 kg?hm-2(Changyou 1) were obtained when 180 kg N?hm-2 was applied with a percentage of organic-fertilizer-N in total N being 15%-30% or 240 kg N?hm-2 with a percentage of organic-fertilizer-N in total N being 10%-20%, which corresponds to application of 1 500-3 000 kg?hm-2 of common compost fertilizer, compared with inorganic nitrogen fertilizer treatment. Compared with inorganic nitrogen fertilizer treatment, a more steady supply of nitrogen could be maintained when certain amounts of organic-fertilizer-N were applied together with inorganic-fertilizer-N. Nitrogen accumulation in 4007 and Changyou 1 were 172.6-256.4 kg?hm-2 and 185.9-235.6 kg?hm-2, respectively, when 180 kg N?hm-2 was applied with a percentage of organic-fertilizer-N in total N being 15%-30% or 240 kg N?hm-2 with a percentage of organic-fertilizer-N in total N being 10%-20%. In these treatments, the highest nitrogen use efficiency was obtained in 4007 (36.6%-48.1%) and Changyou 1 (34.3%-40.0%). 【Conclusion】 Application of mixed mineral-fertilizer-N and organic-fertilizers-N had a better or the same effects on the yields of rice grains and N use efficiency could be significantly increased compared with the single application of mineral nitrogen fertilizer. The best substitution of mineral fertilizer N by organic fertilizer N were 15%-30% or 10%-20% when 180 kg N?hm-2 or 240 kg N?hm-2 was applied in terms of rice fertilization.

Key words: organic-fertilizer-N, mineral-fertilizer-N, substitution rate, grain yields