Long-term pig manure application reduces the requirement of chemical phosphorus and potassium in two rice-wheat sites in subtropical China.

摘要

Producing optimal grain yields while reducing adverse environmental impacts of over-fertilization is essential in intensive, but sustainable, farming systems. We investigated the effects of long-term (1982-2005) application of chemical nitrogen (N), N+chemical phosphorus (P) and N+P+chemical potassium (K) on grain yield, nitrogen recovery efficiency (NRE) and N losses in two rice-wheat sites in subtropical China where pig manure was applied (Suining and Wuchang). Four (Suining) or five (Wuchang) treatments were examined: no-fertilizer, chemical N plus manure (NM), chemical NP plus manure (NPM), chemical NPK plus manure (NPKM) or chemical NPK plus 1.6 times manure (NPKhM, Wuchang only). Fertilizers resulted in 1.5-2.5 times higher grain yields than no-fertilizer, which led to a NRE in the range from 21.0 to 58.3%. Grain yields of rice and wheat were significantly increased by 22.6-25.9 and 34.4-37.5%, respectively, under NPM and NPKM (similar to each other) compared to NM at Suining. Yields were similar for NM, NPK, NPKM and NPKhM at Wuchang. The N accumulation and NRE among fertilizers were in the order NM < NPM=NPKM at the low amount of manure-applied site (Suining), but NM=NPM=NPKM at the high amount of manure-applied site (Wuchang). The ratio of N losses to total N input was 21.4-49.1% at the studied sites. Soil total N accumulated at a rate of 0.01-0.04 g/kg/yr during 1982-2005 with fertilizers and decreased or was constant in soil without fertilizer. Application of chemical P and K fertilizers could be reduced or eliminated after long-term manure application at these two sites, while maintaining optimal grain yields and enhancing soil N accumulation.