Diffusion Characteristics Of Slow-release Fertilizer And Efficient Fertilization Model In Rice-wheat Rotation System

Nitrogen(N)fertilizer plays an important role in agricultural production,but low N use efficiency(NUE)is the key factor limiting the agricultural development.NUE in China is lower than that in developed countries,and excess N application is widespread in China.Coated urea can effectively reduce N loss and improve NUE by slowly releasing nutrient compared with common urea.Otherwise,its economic and efficient application should be based on the reasonable agricultural management practices.According to the needs of the practical production,three coated urea with different release time(30d?60d?90d namely as PCU30?PCU60?PCU90)and urea(U)were used in this research.This study comprised three expriments:1)to study the effect of coated urea fertilization pattern on nutrient absorption and utilization of rice and wheat via in situ micro area field experiment.2)to discuss the characteristics of inorganic N migration for the different types of fertilizer and different fertilizer application patterns via micro frame experiment.3)to analyze the efficient application of coated urea with appropriate proportion in consideration of economic factors via field experiment.The main conclusions were as follows:(1)The fertilization pattern of coated urea significantly influenced diffusion characteristics of inorganic nitrogen in upland.The ability of retaining N fertilizer was ordered as banded at 10cm depth>mixing at 5 cm topsoil>broadcasting on soil surface.For banded at 10 cm depth,urea and PCU30 showed that the nutrient released relatively fast,high inorganic N content was remained in soiland the N fertilizer widely diffused.Content of inorganic N was the lowest for PCU 90 than that for U,and it followed by PCU30.PCU90 showed the lowest released rate.PCU60 was suitable for wheat and guaranteed N uptake by wheat because it released small amount of nutrient at wheat early stage when it small demand and released large amount of inorganic N during 60-150d when it large demand for wheat.(2)Fertilization pattern of coated urea greatinfluenced diffusion characteristics of inorganic nitrogen in the paddy field.Point placement at 10 cm depth significantly increased inorganic N content at the topsoil compared with other fertilization patterns.Urea and PCU30 released relative fast and widely,and increased inorganic N content.While for PCU60,it only enhanced inorganic N content before 90d.For PCU90,inorganic N content was relatively lower at first 30d,and it released fast during 60d to 90d,and the inorganic N content reached the highest amount after 90d.(3)Control-release time and fertilization patterns of coated urea significantly affect wheat yield and N uptake.Wheat yield and agronomical efficiency of U and PCU30 were significantly lower than farmer fertilizer practice(FFP)when it fertilized at 12cm depth and banding at lateral 3 cm and 5 cm depth.It indicated that further banding was better than close banding or directly fertilization under seed of the quickly released fertilizer.The wheat yield of PCU60 was higher than FFP regardless of fertilization patterns.And the yield and NUE of banding at lateral 3 cm and 5 cm depth increased by 6.5%and 17.3%,respectively,compared with FFP.However,different yield reduction was observed for PCU90 compared with FFP.Grain N content of the coated urea was higher than FFP and urea which applied at the same fertilizer pattern.N recovery eficiency of PCU30 and PCU60 were significantly higher than FFP,respectively,regardless N fertilization patterns.(4)For flooded rice,significant yield increment was observed for coated urea compared with common urea when N fertilizer was mixed with topsoil,and there was 34.4%,34%and 37.8%yield increment for PCU30,PCU60 and PCU90,respectively,compared with U.Rice yield,NRE,AE of U was lower than these of other fertilizer under the condition of deep hole fertilization,respectively.It indicated that instant soluable fertilizer one-time centralized fertilization could enhance rice yield,dry matter weight,and improve N use efficiency.Abovegroud biomassfor coated urea with deep hole fertilization was significantly higher than that for U,however the harvested index was significantly lower than U.It showed that the coated urea with deep hole fertilization promoted dry matter accumulation of vegetative organs such as straw,and lowered the dry matter allocation proportion of grain.Rice yield,total N accumulation and AE of coated urea was no difference among different coated ureas,which demonstrated that fertilization effect of coated urea was not sensitive to fertilization site.(5)Field experiment result showed that 15%PCU60 and 85%common urea combined application can reduce 15%N rate without yield reduction,at the same time wheat yield was no significant differences from FFP.And for rice,50%PCU60 and 50%urea combined application achieved the highest yield(9.72 t/ha),the yield and NRE showed 3.6%and 8%increment compared with FFP,respectively.Appropriate proportion of coated urea and urea combined application can replace conventional fertilization model,saving time and manpower.