| The Yangtze River basin is an important rice production base in China,and plays an important role in stabilizing rice production and food security.In order to improve the comprehensive benefits of rice fertilization and nutrient management of medium rice in the Yangtze River basin,this study collected field trial data from medium rice growing areas in the Yangtze River basin between 2000 and 2017,obtained parameters through data compilation and data analysis using the QUEFTS model,and optimized and validated the parameters to obtain the following main results.（1）The yield response and utilization characteristics of N,P and K fertilizers applied to middle-season rice in the Yangtze River basin under optimized fertilization conditions were investigated.The average yield of middle-season rice in the Yangtze River basin provinces under optimized fertilizer application measures could reach 9.3 t hm-2,with the highest yield of 10.1 t hm-2 in Anhui Province.The average yield responses of N,P and K fertilizers applied to middle-season rice in the Yangtze River basin were 2.1,0.8 and 0.9 t hm-2,respectively,with average agronomic efficiencies of 11.3,11.3 and 9.2 kg kg-1 and average partial factor productivity of 49.8,126.7 and 92.9 kg kg-1,respectively.Compared with farmers’fertilization based on their experience and habits,optimized fertilization measures increases rice yields by an average of 0.7 t hm-2,and the application of nitrogen,phosphorus and potassium fertilizers can achieve agronomic efficiency with an increase of more than 35%.Jiangsu Province has the highest yield increase effect with an average increase of 6.4%,and Guizhou Province has the highest yield increase effect of phosphorus and potassium application with an average increase of more than 15%.（2）The Meta-analysis method was used to explore the yield-increasing effect of middle rice in the Yangtze River Basin after fertilization.The application of nitrogen,phosphorus and potassium fertilizers in the provinces and cities in the Yangtze River Basin achieved 35.1%,10.9%and 11.9%increase in the yield of middle rice,respectively.The yield-increasing effects of nitrogen,phosphorus,and potassium fertilizers were the best in low-fertility soils,with yield increase rates of 45.9%,15.1%,and 17.0%,respectively.The range of yield increases for the application of nitrogen,phosphorus and potassium fertilizers was 20.2%to43.9%,0.6%to 16.4%and 6.4%to 16.1%,respectively.The yield-increasing effect of fertilizer application was influenced by soil p H,organic matter and soil nutrient content.The yield-increasing effect of nitrogen application was best in alkaline soil with 39.0%yield increase.In contrast,both phosphorus and potassium applications were highest in weakly acidic soils,with yield increases of 14.1%and 15.7%,respectively.Soil organic matter content had a significant effect on the yield-increasing effect of N and K fertilizer application,but not on the yield-increasing effect of phosphorus fertilizer.The yield-increasing effects of soil total nitrogen,fast-acting phosphorus and fast-acting potassium applications at different levels of content were significantly different;the yield-increasing effects of rice phosphorus applications at different levels of soil total potassium and fast-acting phosphorus content were significantly different.（3）The QUEFTS model was applied to simulate aboveground and seed nutrient uptake at different target yields.The above-ground nutrient requirements for producing 1 ton of middle-season rice yield were 16.1,2.8 and 19.4 kg of N,P and K,respectively,while the seed requirements were 10.2,1.8 and 2.4 kg of N,P and K,respectively.When the set rice target yield reached 80%of the potential yield,the ratios of nitrogen,phosphorus and potassium nutrient uptake of the seeds to aboveground nutrient uptake were 62.8%,64.8%and 12.1%,respectively.（4）Optimized recommended fertilizer application parameters for a nutrient expert system of middle-season rice in the Yangtze River Basin.The average soil base nutrient supply of 100.5,22.5 and 166.4 kg hm-2 for N,P and K,respectively,reached 62.7%,79.8%and 86.1%of the total crop requirement.The relative yields corresponding to low,medium and high supply levels of soil base nutrients in the middle rice region of the Yangtze River Basin were 0.67,0.76 and 0.84 kg kg-1 for N,0.84,0.90 and 0.95 kg kg-1 for P,and 0.86,0.92 and 0.95 kg kg-1for K.The linear relationship between yield response and relative yield was negatively correlated,the relationship between agronomic efficiency and yield response showed a quadratic parabola curve,and the fertilization amount had a negative logarithmic correlation with partial productivity.（5）Results verified in field trials showed that the nutrient expert system optimized fertilizer dosage and improved rice yields.Compared with farmers’customary fertilization and soil testing,the nutrient expert system recommended fertilization treatments applied 20.6%and6.7%less N,but yield increased by 6.9%and 1.1%,respectively.Compared to farmers’customary fertilizer application,the nutrient expert system recommended fertilizer application improved fertilizer agronomic efficiency,partial factor productivity and recovery efficiency,with increases of 5.1 kg kg-1,10.3 kg kg-1 and 16.4 percentage points for nitrogen,4.9 kg kg-1,14.2 kg kg-1 and 6.0 percentage points for phosphorus,and 3.2 kg kg-1,17.0 kg kg-1 and 7.7percentage points for potassium,respectively.Comparing to the soil testing application,the agronomic efficiency of N,P and K fertilizers increased by 2.4,1.1 and 2.3 kg kg-1,respectively,and the recovery efficiency of N fertilizer increased by 7.2 percentage points,respectively.And as for partial factor productivity,it increased by 23.3,4.1 and 34.4 kg kg-1,respectively.In summary,the multi-year field trials of middle rice in the Yangtze River Basin show that in the application practice in the Yangtze River Basin,this rice nutrient expert system based on yield response and agronomic efficiency can achieve obvious results,and realize the fertilizer dosage.Therefore,the fertilizer utilization rate can be significantly enhanced,and the recommended fertilization can be carried out in the cultivation of middle rice in the Yangtze River Basin. |
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