Effects Of Water And Nitrogen Application On Crop Yield And Water And Nitrogen Utilization Under Different Nitrogen Fertilizer Synergist

It is of great significance to study the effects of nitrogen synergist type and water and nitrogen dosage on winter wheat/summer maize yield,water and nitrogen use efficiency and soil nitrate nitrogen residue,which is of great significance to guide winter wheat/summer maize water and nitrogen management.The field experiment was conducted in Wugong County,Shaanxi Province from October 2018 to October 2019.The experiment adopted a split zone design,with water treatment as the main area,nitrogen application as the subplot,and the type of nitrogen synergist as the vice secondary area.The main treatment was composed of low water 30mm（W1）,middle water 60mm（W2）and high water 90mm（W3）;The secondary treatment was composed of low nitrogen 75 kg/hm²（N1,wheat）or 90 kg/hm²（N1,maize）,medium nitrogen 150 kg/hm²（N2,wheat）or 180 kg/hm²（N2,maize）and high nitrogen 225 kg/hm²（N3,wheat）or high nitrogen 270 kg/hm²（N3,maize）;The vice secondary treatment was composed of nitrogen fertilizer synergist types:urea+urease inhibitor（NBPT）,urea+double effect inhibitor（NBPT+DCD）,using traditional fertilization（CO）as the control.In addition,one treatment without nitrogen application was set as control under three water levels.To study the effects of nitrogen synergist types and water and nitrogen dosage on winter wheat/summer maize yield and water and nitrogen utilization,in order to provide reference for water and nitrogen management of crop quality and efficient production.The main results are as follows:（1）The effects of nitrogen synergist type and water and nitrogen dosage on the yield of winter wheat/summer maize were investigated.Irrigation level,nitrogen application level and type of nitrogen fertilizer synergist had significant effects on the yield of winter wheat/summer maize.The yield of winter wheat/summer maize increased first and then decreased with the increase of irrigation amount/nitrogen application rate,and the yield under NBPT and NBPT+DCD treatment was significantly higher than that under CO treatment.The interaction between irrigation level and type of nitrogen fertilizer synergist had a significant effect on the yield of winter wheat/summer maize.With the increase of irrigation amount,the yield increasing effect of nitrogen fertilizer synergist first increased and then decreased.The highest yield of Winter Wheat under CO treatment,NBPT treatment and NBPT+DCD treatment were 143-247kg/hm²,139-183 kg/hm² and 149-185 kg/hm²,respectively.The irrigation interval was 49-63mm,47-67 mm and 50-65 mm,respectively.The corresponding yield interval was 5912-6443kg/hm²,7037-7409 kg/hm² and 7923-8329 kg/hm².The highest yield of summer maize under CO treatment,NBPT treatment and NBPT+DCD treatment were 154-171 kg/hm²,159-175kg/hm² and 162-179 kg/hm²,respectively.The irrigation interval was 62-68mm,61-67mm and60-66mm,respectively.The corresponding yield interval was 8397-8473 kg/hm²,9051-9166kg/hm² and 9789-9926 kg/hm².（2）The types of nitrogen synergist and the amount of water and nitrogen for winter wheat/summer maize to obtain higher water use efficiency were determined.Irrigation amount,nitrogen application amount and type of nitrogen fertilizer synergist had significant effects on WUE of winter wheat/summer maize.WUE of winter wheat/summer maize under W2 irrigation and N2 nitrogen application was higher than that under other treatments,and WUE of two nitrogen synergist types was higher than that under urea treatment.The interaction between irrigation level and type of nitrogen fertilizer synergist had a significant effect on WUE of winter wheat/summer corn.Compared with the irrigation amount of 30mm,when the irrigation amount increased to 60mm,the WUE effect of nitrogen synergist treatment increased by 0.05 kg/m³（winter wheat）and 0.03 kg/m³（summer maize）on average compared with t CO treatment;when the irrigation amount continued to increase to 90mm,the effect of nitrogen synergist on increasing WUE decreased by 0.1 kg/m³（winter wheat）and0.07 kg/m³（summer maize）on average compared with CO treatment.The WUE under NBPT and NBPT+DCD treatment was higher than that under CO treatment.According to the binary quadratic effect equation between WUE and irrigation amount and nitrogen application rate,WUE of winter wheat/summer maize under NBPT+DCD treatment was the maximum.The WUE of winter wheat reached the theoretical maximum WUE with 182 kg/hm² of nitrogen application and 42 mm of irrigation water,which was 33.47%higher than that of CO treatment.The theoretical maximum WUE of summer maize was 157 kg/hm²,and the irrigation amount was 56 mm,which was 17.13%higher than that under CO treatment.（3）The effects of nitrogen synergist and the amount of water and nitrogen on physiological nitrogen utilization efficiency of winter wheat/summer maize and soil nitrate nitrogen residue were revealed.The NPE of winter wheat/summer maize was firstly increased and then decreased with the increase of irrigation amount,nitrogen application amount and nitrogen synergist type.The interaction between the type of nitrogen synergist and the amount of irrigation had a significant effect on the NPE of winter wheat/summer maize.With the increase of the amount of irrigation,the effect of nitrogen synergist on the increase of NPE of winter wheat/summer maize firstly enhanced and then decreased.According to the binary quadratic effect equation of NPE,irrigation amount and nitrogen application amount,the theoretical maximum NPE of winter wheat/summer maize under the two nitrogen fertilization increased by 21.07%and 43.19%,9.56%and 69.54%,respectively,compared with CO treatment.Irrigation level had a significant effect on soil nitrate nitrogen residue in 0-160cm soil layer of winter wheat,but had no significant effect on summer maize.Nitrogen application level and nitrogen synergist type had significant effects on soil nitrate nitrogen residue of winter wheat/summer maize.With the increase of nitrogen application rate,the soil nitrate nitrogen residue of winter wheat/summer maize increased,and tne NBPT treatment and NBPT+DCD treatment reduced nitrate nitrogen residue by 26.79%and 33.93%,15.79%and26.32%,respectively,compared with CO treatment.The soil NO₃^--N residue of CO,NBPT and NBPT+DCD treatments reached the maximum at 90mm irrigation and 225kg/hm²nitrogen application for winter wheat,and at 90mm irrigation and 270kg/hm² nitrogen application for summer corn.In winter wheat/summer maize,the NBPT and NBPT+DCD treatments were 36.81%and 41.21%,22.73%and 30.00%less than the CO treatment in the0-160 cm soil layer under irrigation and nitrogen level,respectively.（4）The recommended amount of irrigation and fertilization under each treatment was calculated by regression analysis and frequency analysis.The recommended amount of nitrogen application under CO,NBPT and NBPT+DCD treatment were 165-170 kg/hm²,164-167 kg/hm²,158-165 kg/hm²,respectively.The recommended irrigation intervals were 50-55mm,53-60 mm,50-55 mm,respectively,and the corresponding yield ranges were 6404-6436kg/hm²,7262-7370 kg/hm²,and 8214-8329 kg/hm²;WUE range was 1.60-1.62 kg/m³,1.82-1.87 kg/m³,2.12-2.15 kg/m³;NPE interval was 42.54-42.83 kg/kg,48.47-49.43 kg/kg,and58.43-59.32 kg/kg,respectively.The recommended nitrogen application rates of CO,NBPT,and NBPT+DCD treatments were 158-170 kg/hm²,159-174 kg/hm²,163-179 kg/hm²,and the recommended irrigation intervals were 67-68 mm,62-65 mm,and 62-64 mm,respectively.The corresponding yield intervals were 8405-8429 kg/hm²,9088-9155 kg/hm²,and 9799-9902kg/hm²,respectively.WUE ranges were 1.80-1.81 kg/m³,1.95-1.97 kg/m³ and 2.11-2.12kg/m³,respectively.The NPE interval was 21.35-21.40 kg/kg,32.01-32.15 kg/kg,and 32.01-32.15 kg/kg,respectively.