Effects Of Different Water-Saving Technologies On Water Use Efficiency,Nitrogen Use Efficiency And Crop Yield Under Dryland Farming Systems

Dryland accounts for 83%of global agricultural areas,covering about 1.4 billion hectares.In China,dryland agriculture accounts for 55%of the total arable land and produces 43%of the national grain demands.It has been playing an important role in stabilizing the country’s grain security.Under the conditions of drought,water shortages,and worsening soil degradation,coordinating water and fertilizer management for dryland agricultural development is a major strategy to ensure food security and ecological environment construction.It is also a scientific problem faced by the international community.To solve the above problems,this study used long-term positioning and indoor tests to analyze the effects of main dryland agricultural practices（organic substitution,plastic film mulching,no-tillage,and Arbuscular mycorrhizal agents）on crop productivity,and water and nitrogen（N）use efficiencies.Effect of chemical to organic fertilizer substitution on crop yield,water use efficiency（WUE）,and soil N pools.After five-years of 270 kg ha^-1 N equivalent fertilizer substitution treatments,the distribution of soil N pools in 0-100 cm profile depths and grain yield and water use efficiency（WUE）of winter wheat were analyzed.The changes of soil aggregate stability and aggregate’s N content in 0-30 cm topsoil layers were also studied.The experiment was established at the dryland water-saving experimental station of the Hebei Academy of Agricultural Science（HAAS）,Hengshui,Hebei province,China,with four treatments:（1）organic manure（OM）,with 100%N from composted cattle manure;（2）organic manure with nitrogen fertilizer（OM+NF）,with 50%N from composted cattle manure plus 50%N from urea;（3）nitrogen fertilizer（NF）,with 100%N from urea;and（4）control（CK）,with zero N fertilization.Results found that the grain yield and WUE of wheat were improved（p<0.01）with N fertilization,irrespective of the N sources applied.Compared to CK,the grain yield of wheat under OM,OM+NF,and NF treatments was increased by 103.5%(3332.10 kg ha^-1),109.2%(3516.05 kg ha^-1),and 128.6%(4139.51 kg ha^-1),respectively.The WUE of wheat under OM,and OM+NF and NF treatments was improved by 75.2%,82%,and 73.7%,respectively.The correlations among N fertilization,crop evapotranspiration,and grain yield were positively significant（p<0.01）.The OM and OM+NF treatments significantly increased（p<0.05）the content of soil total N（STN）,soil organic C（SOC）,particulate organic N（PON）,microbial biomass N（MBN）,dissolved organic N（DON）,and NO3content in 0-20 cm topsoil depths.Conversely,the NF treatment resulted in the highest（p<0.01）DON and NO3-depositions in 40-100 cm subsoil depths.Compared with CK,the average STN content of OM,OM+NF,and NF treatments was increased by 32.9%（0.27 g kg-1）,8.4%（0.07 g kg-1）,and 8.7%（0.07 g kg-1）,respectively.The average SOC content of OM,OM+NF,and NF treatments also increased by 65.2%（4.42 g kg-1）,38%（2.57 g kg-1）,and 21.6%（1.46 g kg-1）,respectively.The NH4+contents in selected profile depths were significantly highest（p<0.01）under OM treatment.The correlations between STN and its fractions were positively significant at 0-10 cm and 10-20 cm topsoil depths.The OM and OM+NF treatments increased the proportion of>1 mm macroaggregate fractions in 0-10 cm bulk soil by 42.6 to 87.9%,and the proportion of>0.5 mm macroaggregate in 10-20 cm soil by 26.39 to 66.02%.The OM and OM+NF treatments reduced the proportion of microaggregates（<0.25 mm）in 0-10 cm and 10-20 cm bulk soils,by 15 to 37.9%and 19.9 to 53.2%,respectively.The average mean weight diameter（MWD）of water-stable aggregates in 0-30 cm bulk soils under OM and OM+NF treatments increased,by 35.7%and 22.274%,respectively.Total N content in each aggregate fraction of 0-10 cm and 10-20 cm bulk soils under OM and OM+NF treatments were increased by 12.2 to 50.7%and 31.3 to 98.8%,respectively.In general,0-20 cm bulk soil’s>0.5 mm macroaggregates contributions to soil TN were increased under OM and OM+NF treatments.The differences between NF and CK treatments in most of the selected parameters were non-significant（p>0.05）.Effect of plastic film mulching（PFM）on grain yield,WUE,NUE,and soil N pools.The experiment was conducted at the Fuxin Agricultural Environment and Farmland Conservation Experimental Station of the Ministry of Agriculture and Rural Affairs in Fuxin Country,Liaoning Province,China.The effects of plastic film mulching on grain yield,WUE,NUE,and soil N pools under a spring maize growing dryland farming system were analyzed.Results found that PFM significantly increased（p<0.05）maize grain yields,WUE,NUE,total N accumulation in biomass and grain,and improved soil total N（STN）and its fractions levels in topsoil layers.The grain yields of maize under PFM were higher(9450.28 kg ha^-1 in 2020 and 8580.14 kg ha^-1 in 2021)and increased by 36.3%and 23.9%over the NM treatment in the 2020 and 2021 growing seasons,respectively.The PFM treatment improved（p<0.01）the WUE of maize by 39.6%and 33.8%in the 2020 and 2021 growing seasons,respectively.The 2-year average NUE of maize under the PFM treatment was 40.1,30.1%greater than the NM treatment.The average STN,PON,and MBN contents under the PFM soil profile increased by 22.3%,51.9%,and 35%,respectively,over the two growing seasons.The fertilizer residual ¹⁵N contents in plant biomass,grain,and the soil TN pool were significantly higher（p<0.05）under the PFM treatment.Under the PFM treatment,cumulative NH3 volatilization decreased,but cumulative N₂O gas emissions increased substantially.Effect of tillage on WUE,NUE,and yield of winter wheat.The experiment was conducted at the Linfen Experimental Station of Long-term Conservation Tillage in Shanxi Province（since 1992）.The effects of notillage and conventional tillage on WUE,nitrogen utilization,and crop yield in 2020 and 2021 were analyzed.Compared to CT,wheat yield and WUE under NT treatment were significantly increased（p<0.05）.During the 2020 and 2021 growing seasons,the wheat yield under NT treatment increased by 18.1%(910 kg ha^-1)and 24.0%(1207 kg ha^-1),respectively.The WUE of NT treatment was 8.73 and 8.88 kg ha^-1 mm-1 in the 2020 and 2021 growing seasons,respectively.It was 18.1%and 29.7%greater than that of CT.During the 2020 and 2021 growing seasons,the total nitrogen uptake of wheat under NT was 12.5%(16.5 kg ha^-1)and 16.4%(19.1 kg ha^-1)higher（p<0.05）than that under CT,respectively.Compared with CT,the NUE of wheat under NT increased by 18.3%in 2020 and 29.8%in 2021.In both growing seasons,the soil N uptake by winter wheat under NT treatment was significantly higher than under CT,indicating that crop plants under NT were more inclined to absorb and utilize soil nitrogen.Effects of arbuscular mycorrhizal fungi（AMF）on plant growth and nitrogen uptake in maize.The effects of AMF application on maize growth,nitrogen uptake,and straw nitrogen recovery were analyzed using longterm no-tillage（NT）and conventional tillage（CT）soils.Four rhizosphere treatments were established under microcosm ecosystems:（1）NT+AMF,and（2）NT-AMF,were applied in no-tillage soil;（3）CT+AMF,and（4）CT-AMF,were applied in conventional tillage soil.The root length,root surface area,root volume,and biomass accumulation in shoot and root were significantly increased under NT+AMF and CT+AMF treatments after 65 days of culture（50 days of straw placement）.The total N accumulation in each plant of NT+AMF treatment increased by 116%,compared with CT-AMF treatment.NT+AMF and CT+AMF treatments increased（p<0.01）¹⁵N content（%TN）in shoot biomass,root biomass,plant chamber soil,and straw chamber soil.The recovery rate of straw-driven ¹⁵N in NT+AMF was 9.4%,which was 111.8%,78.6%,and 229.1%greater（p<0.01）than the NT-AMF,CT+AMF,and CT-AMF treatments,respectively.The addition of AMF significantly increased maize’s biomass accumulation and nitrogen absorption capacity,and the effect of AMF in the long-term no-tillage soil was better.The results showed that chemical fertilizer substitution with organic manure could improve the productivity,soil fertility and sustainability of dryland farming systems by increasing crop yield,water use efficiency,and the content of water-stable aggregates and labile organic nitrogen in soil.Plastic film mulching could increase spring maize yield,water use efficiency,and nitrogen use efficiency of spring maize,and improve the utilization of soil nitrogen and fertilizer residual nitrogen,but it would increase the N₂O gas emission.No-tillage with straw retuning could increase winter wheat yield and water use efficiency under drought conditions.AMF application could increase maize biomass,root development,nitrogen uptake and straw nitrogen use efficiency under no-tillage and conventional tillage,but it effects could be best in no-tillage dryland soil.