Effects Of Different Irrigation Measures On Water-Nitrogen Use And Greenhouse Gas Emissions In Wheat Farmland

The lack of groundwater resources,inefficient use of agricultural irrigation,high soil nitrogen surpluses and high greenhouse gas emissions in North China have greatly hindered the sustainable development of agriculture.How to achieve agricultural water savings and greenhouse gas emission reductions is an important challenge for food production in the region.In this study,five treatments of surface drip irrigation(DI),shallow buried drip irrigation(SDI),root alternate irrigation(PRI)and flood irrigation(FP)under shallow submerged drip irrigation,and no nitrogen application(CK)under diffuse irrigation were set up in Baimu Village,Jiajiakou Town,Ningjin County,Hebei Province,using a combination of a large field trial and indoor analysis from 2020 to 2022.The wheat yield,water and nitrogen utilization efficiency,farmland greenhouse gas emission characteristics and net greenhouse effect under different irrigation methods were systematically analyzed.The results of the study provide a scientific basis for determining the optimal water-saving irrigation mode in North China.The main conclusions reached were as follows(1)Dry matter accumulation of wheat at maturity DI>SDI>FP>PRI,DI and SDI treatments were more favorable to the accumulation of dry matter of wheat than FP treatment.Nitrogen accumulation in wheat at maturity was SDI>DI>PRI>FP.Nitrogen accumulation in wheat was significantly higher in the DI and SDI treatments by 20.78%and 24.30%compared to the FP treatment,and SDI was the more favorable irrigation pattern for nitrogen accumulation in wheat.The SDI treatment had the highest effective spike number,grain number and yield,and the SDI treatment increased yield by 3.92%～8.87%in both years compared to the other N treatments.PRI treatment wheat had lower water consumption and failed to increase wheat yield.There were no significant differences in N fertilizer use efficiency(ANUE)and N fertilizer bias productivity(PFP)between wheat treatments in 2020-2021.The ANUE of wheat treated by SDI was significantly increased by 63.42%compared with the treatment of FP in 2021-2022;The SDI treatment significantly increased wheat PFP by 9.97%and 12.70%compared to the FP and PRI treatments.Irrigation has a significant impact on wheat water efficiency.The average irrigation water productivity(IWUE)of wheat in the PRI treatment was significantly higher than that in the DI,SDI and FP treatments by 48.58%～191.11%.Followed by the SDI and DI treatments,which were 95.93%and 88.52%higher than the FP treatment,respectively;Water productivity(WUE)of wheat was significantly higher in the PRI treatment than in the DI,SDI and FP treatments by 16.26%～81.62%.This was followed by the SDI and DI treatments,with increases of 56.21%and 50.27%respectively over the FP treatment.(2)Peak soil N2O emissions from the drip irrigation treatment lasted 4-10 days after fertilization application and FP treatments lasted 8 to 11 days after fertilization.Cumulative N2O emissions from the drip irrigation treatment were significantly reduced on average by 41.04%～66.27%in both years compared to the FP treatment.The cumulative emission of N2O under PRI treatment was the lowest,which was 0.52 kg/hm2;Peak soil CO2 emissions from each N application treatment lasted 3-8 days after fertilization.Soil CO2 emissions during the whole wheat growing period mainly occurring at higher soil temperatures between nodulation and maturity,and all drip irrigation treatments reduced soil CO2 emissions in wheat fields.The peak of soil CH4 emissions from the drip irrigation treatment lasted for about 2 days after fertilization application and FP treatment lasted 3 days after fertilization.Compared to the FP treatment,soil CH4 uptake increased by 82.76%～146.55%(2020-2021)and 102.08%～181.25%(2021-2022)in the drip irrigation fertilization treatments,with the highest cumulative soil CH4 uptake of 1.3 9 kg/hm2 in the DI treatment.(3)Drip irrigation reduced indirect greenhouse gas emissions.DI/SDI and PRI reduced indirect greenhouse gases by 16.1%and 29.8%compared with FP.The net greenhouse effect of drip irrigation was reduced by 9.47%～12.37%compared with flood irrigation,and the greenhouse gas emission intensity was reduced by 12.66%～17.90%compared with flood irrigation.Among the drip irrigation treatment,the average net greenhouse effect of wheat field under PRI treatment was the least,and the reduction was 12.48%compared with FP fertilization treatment,followed by SDI treatment,which was significantly reduced by 10.34%compared with FP fertilization treatment.SDI treatment had the lowest GHGI,significantly reducing 17.90%compared with FP treatment.SDI treatment had a lower net greenhouse effect and greenhouse gas emission intensity.The SDI treatment had the highest net yield in both years,with an increase of 547-5676 yuan/hm2 compared to the other N treatments.In summary,the indicators of dry matter accumulation,nitrogen accumulation and water and nitrogen use efficiency of wheat using shallow buried drip irrigation are superior,which not only helps to improve seed yield,increase net income and improve water and nitrogen use efficiency,but also reduces the risk of environmental pollution,and is a scientific irrigation mode suitable for North China to save water,reduce emissions and increase yields.