Nutrient Management Of Winter Wheat In Yangtze Valley Based On Yield Response

The Yangtze Valley is an important wheat production base in China.However,the phenomenon of farmers blindly applying chemical fertilizer in pursuit of high yield has become very common,which leads to the continuous increase of the application amount of chemical fertilizer,which not only reduces the utilization rate of fertilizer and yield benefit,but also has a serious impact on the ecological environment.In view of the current situation of unreasonable nutrient management of winter wheat in the Yangtze Valley,a recommended fertilization method based on yield response and agronomic efficiency for wheat in the Yangtze Valley was established.Based on the field experiment data of wheat in the Yangtze Valley for many years,the Quantitative Evaluation of the Fertility of Tropical Soil（QUEFTS）was adopted to study the characteristics of winter wheat yield and nutrient absorption in the Yangtze Valley,combining the improved Site-specific Nutrient Management（SSNM）technology.The internal relationship of yield response,relative yield and agronomic efficiency was established.Based on which,Nutrient Expert system（NE）for winter wheat of the Yangtze Valley was established,and which was corrected and improved through field validation to study its agronomic,economic and environmental effects.The main research findings were as follows:（1）The average yield of winter wheat under optimal fertilization in the Yangtze valley was6.6 t hm^-2,with the highest yield in An’hui Province(7.3 t hm^-2)and the lowest yield in Chongqing(3.6 t hm^-2).Aboveground nutrient accumulation in different regions was significantly different,which was strongly related to the yield of different regions.Aboveground nutrient uptake in the downstream region was the highest,which was 144.9,27.8 and 94.5 kg hm^-2,respectively.The internal nutrient efficiency of nitrogen and potassium was also the highest in the downstream,and the nutrient internal efficiency of phosphorus in the middle reaches was the highest.The reciprocal internal efficiency of N,P and K was the highest in the upstream,and the variation range of unit nutrient uptake was large.According to the QUEFTS model,the N,P and K nutrient requirements for wheat grain yield of 1000 kg winter wheat in the upper,middle and lower reaches of the Yangtze Valley were 26.0,3.8 and20.2 kg,21.7,3.7 and 19.8 kg,21.1,4.0 and 20.2 kg,respectively.（2）The average yield responses of N,P and K were 2.3,0.9 and 0.6 t hm^-2,respectively,but the variation range was large.Average relative yields of N,P and K were 0.6,0.8 and 0.9,respectively,and N was the main limiting factor for wheat yield.The average agronomic efficiency of N,P and K under optimized fertilization treatment was 12.6,11.6 and 7.7 kg kg^-1,and the average partial factor productivity was 34.0,78.9 and 73.4 kg kg^-1,respectively.（3）The application of N,P and K fertilizer had significant effect on wheat yield in the Yangtze Valley,and the yield increasing rates were 66.0%,18.0%and 10.0%respectively;the difference of basic soil fertility and planting area had significant effect on the yield increasing effect of N,P and K fertilizer application in the Yangtze Valley;the yield increasing effect of N,P and K fertilizer was the best under acid soil conditions and the yield increasing effect decreased with the increase of soil p H;the content of soil organic matter had a significant effect on the yield increase of wheat by phosphorus application;the content of soil total phosphorus,total potassium,alkali hydrolyzable nitrogen,available phosphorus and available potassium had a significant effect on the yield increase of wheat by nitrogen application;the content of soil total phosphorus and available phosphorus had a significant effect on the yield increase of wheat by phosphorus application;the content of soil available potassium had a significant effect on the yield increase of wheat by potassium application.（4）There was a significant linear negative correlation between yield response and relative yield,and there was a significant quadratic function relationship between yield response（x）and agronomic efficiency（y）（P<0.05）.The principle of determining the recommended application rate of NE for winter wheat in the Yangtze valley was defined.Nitrogen application rate was determined by the ratio of N yield response to N agronomic efficiency,while P and K also needed to consider the nutrients needed to maintain soil fertility and the nutrient application status of previous crops.（5）The field validation results showed that,compared with farmers’practices,the NE for winter wheat based on yield response and agronomic efficiency balanced the fertilizer usage and reduced the application of N,P and K by 26.6%,13.3%and 12.9%,respectively.The wheat yield was increased by 365.0 kg hm^-2 on average,the fertilizer cost was reduced by429.0 yuan hm^-2 on average,and the economic effect was increased by 1446.0 yuan hm^-2 on average,of which 55.5%came from the increase of wheat yield.Fertilizer use efficiency of winter wheat in the Yangtze Valley was significantly increased by 6.5,8.3 and 8.6 kg kg^-1,respectively.The partial factor productivity of N,P and K increased by 10.9,17.9 and 24.8 kg kg^-1,respectively.The recoveries of nitrogen,phosphorus and potassium increased by 15.3,11.9 and 27.2 percentage points,respectively.Aboveground nitrogen uptake was significantly increased and nitrogen loss was significantly reduced.Aboveground nitrogen uptake was increased by 15.2%on average,reactive nitrogen loss intensity,total N₂O emission and greenhouse gas emission intensity were decreased by 37.6%,29.4%and 36.5%on average.In conclusion,the NE based on yield response and agronomic efficiency of winter wheat in the Yangtze valley as an alternative fertilization recommendation method is feasible in terms of theoretical support and technical practice,and can be used in winter wheat production areas in the Yangtze valley of China.