Effect of fertilizer management on rice yield, soil organic carbon and total nitrogen based on utilizing the milk vetch

A four-year(2008–2011) long term experiment was carried out to study the effects of different chemical fertilizer management on rice yield,paddy economic benefits,total nitrogen(N) accumulation,soil carbon(C) and nitrogen under the utilization of milk vetch(22 500 kg/hm2).The results were as follows: ①Compared with farmers’ fertilizer practice(FFP),fertilizers application delayed appropriately could increase rice yields.Among all treatments,treatments of 20% or 40% chemical fertilizer cut down could only increase 2.37% and 3.34% grain yield respectively than that of combined treatment of basal fertilizer + tillering fertilizer + panicle fertilizer(the ratio was 3∶4∶3)(Treat1),which was followed by the treatment of basal fertilizer + tillering fertilizer + panicle fertilizer(the ratio was 0∶7∶3)(Treat2).②The appropriate postponed fertilizers application could increase rice output value.Treat1 could increase 3.0% average annual output value,followed by Treat2.③The fertilizers application time postponed could improve total nitrogen accumulation in rice(TNA),N grain production efficiency(NGPE),N partial factor productivity(NPF) and N harvest index(NHI).Treat1was the best one in improving TNA,NGPE,NPF and NHI among all treatments.④The retarded fertilizers application could also increase the content of soil organic carbon(SOC) and soil total nitrogen(TN).Treat1 had the best effect in improving SOC and TN.Through the above comparison,the appropriate retarded use of combined fertilizers,which was composed of 30% basal fertilizer + 40% tillering fertilizer and 30% panicle fertilizer was a better approach for increasing rice yield and for enhancing soil fertility under the condition of utilizing milk vetch.