Application Of The Fertilization Method Based On Nutrient Expert System In Winter Wheat Production In Weibei Dryland

The application of chemical fertilizer is one of the important measures to improve crop yield and quality,but excessive chemical fertilizer input not only causes soil quality degradation and resource waste,but also causes environmental problems,such as high carbon emissions.Therefore,reasonable fertilization and improving fertilizer utilization efficiency are the important solutions to solve these problems.Based on an on-farm survey and the two-year field experiments（conducted in 15 experimental sites in nine counties）in the Weibei dryand of Shaanxi province,this study was aimed to evaluate the current status of fertilization by the farmers and the reduction potential of chemical fertilizer input by the Nutrient Expert System（Nutrient Expert,NE）and clarify the application effect of the recommended fertilization method based on NE system.The wheat yield,economic benefits,partial productivity of fertilizer,economic benefits and nitrate nitrogen residues were determined between the recommended fertilization method based on the NE system（NE）and famers practice（FP）.The study would provide a theoretical and scientific basis for popularizing the recommended fertilization method based on the NE system in the Weibei dryland.The main results are as follows:（1）The survey showed that the average yield of winter wheat in the Weibei Dryland was 4799 kg hm^-2,of which 78.4%were between 3000～7000 kg hm^-2.The average application rates of nitrogen（N）,phosphorus（P）,and potassium（K）fertilizers were 194 kg hm^-2,132 kg P₂O₅ hm^-2,33 kg K₂O hm^-2,with the variation coefficients of 42.8%,57.6%,and 118.8%,respectively.The average soil organic matter content was 13.3 g kg^-1,and 66.7%of the surveyed fields ranged from 11 g kg^-1 to 17 g kg^-1,while the p H were 8.2,with a low variation coefficient（3.4%）.The average total nitrogen（TN）content was 0.8 g kg^-1,with 52%of fields varying from 0.7 to 0.9 g kg^-1.The accumulation of nitrate N in 0-100 cm soil layers was 209 kg hm^-2.The soil available phosphorus content was 17.9 mg kg^-1,with the range of 6.7to39.6 mg kg^-1,while soil available potassium content was 168 mg kg^-1,and 84.9%of fields had the values of 100to 220 mg kg^-1.（2）Based on fertilization method by the NE system,it was found that the average recommended application rates of N,P,and K fertilizers were 132 kg hm^-2,30 kg P₂O₅ hm^-2,and 43 kg K₂O hm^-2,respectively.The amount of N and P fertilizer input was significantly reduced by 32%and 77%,respectively,but that of K fertilizer was increased by 34%.The economic fertilizer input and benefits in the fertilization method based on NE were 3484yuan hm^-2,7074 yuan hm^-2,which was lower 16.3%for input and higher 10.7%for benefits.Furthermore,compared with the farmers’practices,NE system can significantly reduce the loss of active nitrogen by 34%and greenhouse gas emissions by 31.1%.These indicated that the recommended fertilization method based on NE system had the potential to reduce fertilizer input,increase nutrient use efficiency,and reduce environmental risks.（3）Field experiments at 15 sites showed that the average application rates of N and P fertilizers in the NE treatment were 158 kg N hm^-2 and 62 kg P₂O₅ hm^-2,which significantly reduced by 18%and 54%,respectively compared with the FP treatment.However,the average application rate of K fertilizer was 40 kg K₂O hm^-2,with an increase of 43%comparing with that of the FP treatment.The average wheat grain yield in the NE treatment was 5171 kg hm^-2,which was similar to that of the FP treatment.The wheat grain yield varied at different experimental sites,with lowest yield of 911 kg hm^-2 at Pucheng site and highest yield of 7529 kg hm^-2 at Qishan site in the 2018?2019 season.There were also differences in winter wheat grain yield between the different experimental years,with high yield(5996 kg hm^-2)in the 2017?2018 season and low yield(4571 kg hm^-2)in the2018-2019 season.（4）Overall,the economic benefit of the NE treatment was higher by 7.8%than that of the FP treatment,however,it varied at different sites and experimental years.The highest economic benefit was 12636 yuan hm^-2 at Qishan site while the lowest benefit was-1870yuan hm^-2 at Pucheng site because of the dry climate.The partial productivity of N and P fertilizers in the NE treatment was increased by 25.1%and 139.8%,respectively comparing with the FP treatment.There was no significant difference in the nitrate N residual in the0-100 cm soil layer between the NE and FP treatments,but the NE treatment decreased nitrate N by 56.3%at Duma,Yongshou county site in the 2018?2019 season,and by 29.4%and 33.7%,respectively at Binxian site for two consecutive years,increased nitrate N by104.1%and 50.5%,respectively at Pucheng site for two consecutive years.The results showed that the nitrate N residues in soil should be considered comprehensively when using the NE system to recommend fertilization on drylands,in order to achieve more economic benefits and reduce environmental risks.In summary,the recommended fertilization method based on the NE system had the potential to lower fertilizer input and greenhouse gas emission and get high benefit.The field experiment confirmed that the recommended fertilization method based on the NE system not only guaranteed the wheat yield,but improved the partial productivity of N and P fertilziers and economic benefits.It had reduced N and P fertilizer application rate and increased incomes.The results suggested that the fertilization method can be used for winter wheat production in drylands.However,the fertilization method may need to be further optimized based on rainfall changes in the northwestern region.In addition,the impact of the method on deep soil nitrate residues and the benefits of long-term application still need to be further investigated.