Nitrogen Residual Characteristics And Availability On Typical Farmlands Under Different Fertilization In China

According to many reports,the 30% of nitrogen use efficiency?NUE?in our country is far lower than 50-60% in developed countries.Actually,the traditional calculating method of NUE only considered the nutrient absorption and use of current crop,so it can not reflect the residual and utilizability of nitrogen in the soil.Based on long-term fertilization tests in 6 different ecological climatic regions in China and adding ¹⁵N incubation experiment aimed to simulate the process residual N entering soil and used by plants,this research not only suggested the availability and crop use ratio of different nitrogen component,but also clarified the residual characteristics of nitrogen in typical field under conditions of applying chemical fertilizer,chemical-organic fertilizer and straw turnover,in order to provide theoretical basis for choosing high efficiency manure management and its environmental effects assessment.The results showed as follows:The annual average nitrogen residual efficiency?NRE?is 16.9% in typical farmland of our country during long-term fertilization test.The NRE of paddy,paddy-dry rotation,dry crop is 13.2%,23.9%,13.6% respectively.In treatments of partial fertilizer,the highest NRE is 16.2% in treatment of nitrogen and potassium chemical fertilizer?NK?,the next NRE is 15.8% and 16.0% of treatment of nitrogen and phosphorus chemical fertilizer?NP?and nitrogen,phosphorus and potassium chemical fertilizer?NPK?respectively.The NRE is 21.7% and 19.0% in treatment of nitrogen chemical fertilizer?N?and nitrogen,phosphorus and potassium chemical fertilizer combined with manure?NPKM?in paddy-dry rotation and dry crop respectively.The average NRE is 10.4% in treatment of nitrogen,phosphorus and potassium chemical fertilizer combined with straw?NPKS?in paddy and dry crop.In adding ¹⁵N incubation experiment,the highest nitrogen holding efficiency?NHE?is 22.2% in treatment of no fertilizer?CK?,the lowest is 13.7% in treatment of NPKM;NHE are 16.8% and 18.1% in NPK and NPKS treatments respectively.NHE is the lowest in fine free particulate organic nitrogen?ffPON?;the next is intraaggregate particulate organic nitrogen?iPON?.NHE in NPK and NPKM treatments are 1.80% and 1.69% lower than CK respectively in coarse free particulate organic nitrogen?cfPON?.NHE in other treatments are 1.29%-3.70%,2.18%-3.19% lower than CK treatment in mineral associates soil organic nitrogen?mSON?inside of Micro aggregate and mSON out of Micro aggregate.In cfPON,the highest effective rate of holded N is 19.0% in NPKM treatment,the next is 16.8% in NPK treatment;the lowest is 13.9% in both CK and NPKS treatments.The effective rate of holded N is 12.1%,10.9%,6.27%,5.66% in CK,NPK,NPKS treatments,and NPKM respectively in iPON.The lowest effective rate of holded N is 2.99%-4.85% in mSON inside of micro aggregate,in which CK is 1.37%-1.86% lower than three other treatments.The effective rate of holded N is 12.4%-23.1% in mSON inside of micro aggregate of different fertilization treatments,which of the NPK is 9.22%-10.8% higher than three other treatments.