Responses Of Crop Yield And Nitrogen And Phosphorus Use Efficiency To Chemical Nitrogen Substitution By Manureunder A Winter Wheat-summer Maize Rotation System On Lou Soil

In order to take advantage of organic manure and reduce chemical fertilizer application and simultaneously keep crop productivity and high nutrient use efficiency.The objective of this study was to investigate the responses of crop yield and nitrogen and phosphorus use efficiency to chemical nitrogen substitution by manure under a winter wheat–summer maize rotation system through a stationary experiment since October 2014.The experiment involved six treatments as no fertilizer?CK?,synthetic N,phosphorus?P?and potassium?K?fertilizers alone?NPK?,75%NPK+25%organic N through manure?25%M?,50%NPK+50%organic N?50%M?,25%NPK+75%organic N?75%M?,100%organic N?100%M?.The main results obtained were as follows:1)Different fertilization treatments significantly increased the number of wheattillers,and treatments of 50%M and 75%M showed the highest numbers.The biomass of different fertilization treatments in the wheat season was in a decrease order as:M>NPK>CK,and NPK>M>CK in maize season.Fertilization significantly increased crop yield in both wheat and maize season,and with the increase of organic nitrogen input,crop yields increased firstly and then decreased.In wheat season,the yield under manure treatments were significantly higher than that under chemical fertilizer treatment.In maize season,the yields of 50%M and75%M treatments were similar to that of NPK,while the yields in 25%M and 100%M treatments were significantly lower than that of NPK.The total yield of wheat and maize varied from 9166 to 17496 kg·ha^-1,and 50%M and 75%M treatments produced significantly higher yields than NPK did,while 25%M and 100%M treatments had no significant differences in yield relative to NPK.Overall,the highest crop yield was under 50%-75%M with high harvest index.2)During the wheat–maize rotation,the nitrogen physiological efficiencies among treatments were 34-47 kg·kg^-1,the partial nitrogen productivity was 44-51 kg·kg^-1,the agronomy efficiency of nitrogen was 18-24 kg·kg^-1and the nitrogen recovery range was38⁶1%.The nitrogen efficiency indicators were generally highest under 50%-75%M treatments.The phosphorus physiological efficiency of different treatments was in the range of 243-870 kg·kg^-1,the phosphorus partial productivity was 99-230 kg·kg^-1,the phosphorus agronomic efficiency was 40-89 kg·kg^-1,the phosphorus recovery range was 9-18%and phosphorus balance indexwas 31-47%.The indicators of phosphorus efficiency were gradually decreased with the increase of the organic fertilizer replacement ratio except phosphorus recovery rate.3)The nitrogen budget showed 0.4-80.6 kg N·ha^-1 surplus under 50-100%M treatments during wheat-maize rotation year,and 100%M treatmentshowed the largest number.However,the nitrate-nitrogen residue under 50-100%M treatments was significantly lower than thoseunder25%M and NPK treatments.The phosphorus budget indicated P application was more than crop requirement inall treatments,andsurplus was ranged from 35?NPK?to 108kg·ha^-1?100%M?.4)The economic benefits was highest in 50-75%M treatments and lowest in 100%M treatment.On the whole,replacing 50-75%of chemical N with organic manure can significantly increasecrop yield and nitrogen use efficiency,and reduce soil nitrate-N residues,but phosphorus surplus was high in tested experimental year.However,How these treatments will affect crop productivity and nutrient efficiency over time,it needs further investigation.