Effects Of Water And Fertilizer Integration On Maize Yield And Water-Nitrogen Use Efficiency Under Micro-Sprinkler Irrigation

In the North China Plain,traditional irrigation and fertilization methods can lead to low water-nitrogen use efficiency of maize.In order to achieve stable and high yield of maize and efficient utilization of water-nitrogen resources.an experimental study on the effects of nitrogen fertilizer reduction on soil water-nitrogen distribution and use efficiency,growth and development and grain yield of summer maize under micro-sprinkler irrigation was carried out in Tai’an,Shandong during 2020 and 2021 growing season.Border irrigation and traditional fertilization mode were set up as control treatment（CK）.The integrated water and fertilizer treatment of micro-sprinkler supplementary irrigation was set up based on the water content of 0-20 cm soil layer.Five nitrogen rates(WN₂₄₀:240 kg/hm~2,WN₂₁₀:210kg/hm~2,WN₁₈₀:180 kg/hm~2,WN₁₅₀:150 kg/hm~2,WN₀:0 kg/hm~2)were set in this experiment.The supplementary irrigation was applied at sowing,jointing,big trumpet stage and silking stages of summer maize.The lower limits of irrigation were 70%,60%,65%and 65%of field capacity,respectively;and the upper limits were field capacity.The nitrogen application period was consistent with that of the supplementary irrigation.The nitrogen application ratio was 1:2:5:2,applied with the irrigation water.The CK treatment was only irrigated once after sowing,and the irrigation method was surface border irrigation.The application rate of nitrogen fertilizer was 270 kg/hm~2,50%of which was applied during sowing stage,the other50%of which was applied before rainfall in the big trumpe stage.The main results are as follows:（1）Under the condition of micro-sprinkler irrigation with water and fertilizer integration,at the same period,the distribution characteristics of soil moisture and nitrate nitrogen profile in 0-100 cm soil layer of summer maize were similar.With the increase of nitrogen application rate,the soil moisture content generally showed a decreasing trend,while the nitrate nitrogen content showed an increasing trend.With the advancement of maize growth process,soil moisture and nitrate nitrogen content in each treatment showed an increasing and decreasing respectively.During the maize was harvested in 2021,compared with high nitrogen treatrend,tment(WN₂₄₀),the residues of nitrate nitrogen in 0-100 cm soil layer of WN₂₁₀,WN₁₈₀,WN₁₅₀and WN₀treatments decreased by 15.36%,36.83%,35.54%and50.77%,respectively.（2）Increasing nitrogen application rate under the integration of micro-sprinkler irrigation with water and fertilizer could promote the plant height,stem diameter,leaf area index and aboveground dry weight of maize.However,when the nitrogen application rate increased to a certain extent（180 kg/hm~2）,the promoting effect was weakened.Compared with the high nitrogen treatment(WN₂₄₀),the morphological development indexes of maize under WN₂₁₀and WN₁₈₀treatments had no significant difference.The integration of micro-sprinkler irrigation with water and fertilizer could still ensure the normal growth and development of maize with nitrogen application rate reduced.Compared with CK treatment,there was no significant difference in plant height,stem diameter,leaf area index and other indexes of maize under WN₁₈₀,WN₂₁₀and WN₂₄₀treatments.With the increase of nitrogen application rate,the dry matter transport amount,transport efficiency and contribution rate of transport amount in maize vegetative organs to grain first increased and then decreased,and the corresponding nitrogen application rate at the maximum value was 180～210kg/hm~2.Compared with CK treatment,the dry matter transport amount,transport efficiency and contribution rate of transport amount in maize vegetative organs to grain were all increased under WN₁₈₀,WN₂₁₀and WN₂₄₀treatments.Among them,the dry matter transport amount,transport efficiency and contribution rate of transport amount in maize vegetative organs to grain under WN₁₈₀treatments were significantly increased by 10.40%～23.19%,10.80%～18.11%and 13.66%～26.16%,respectively.（3）Under the condition of water and fertilizer integration of micro-sprinkler irrigation,nitrogen application rate and year had extremely significant effects on nitrogen accumulation in summer maize at mature stage,and their interaction had significant effects.With the increase of nitrogen application rate,the nitrogen accumulation in the whole maize plant gradually increased,but the nitrogen transport amount,nitrogen transport efficiency,and the contribution rate of nitrogen transport to grain first increased and then decreased.The maximum nitrogen application rate was 180～210 kg/hm~2.The integration of micro-sprinkler irrigation with water and fertilizer can promote the absorption and utilization of nitrogen in maize plants.Compared with CK treatment,WN₂₄₀,WN₂₁₀and WN₁₈₀treatments could significantly increase the nitrogen accumulation in maize leaves,grains and whole plants,and effectively improve the nitrogen transport amount,nitrogen transport efficiency and the contribution rate of nitrogen transport to grains.（4）Under the integration of water and fertilizer of micro-sprinkler irrigation,nitrogen application rate had a significant effect on maize grain yield,while year and their interaction had no significant effect on grain yield.With the increase of nitrogen application rate,the grain yield of maize showed a increasing trend.Compared with the high nitrogen treatment(WN₂₄₀),the grain yield of maize decreased by 3.42%～4.06%,4.41%～5.72%,11.28%～12.77%and 20.09%～22.69%under the treatments of WN_210,WN₁₈₀,WN₁₅₀and WN₀,respectively.The differences between the treatments of WN₁₅₀and WN₀reached the significant level.Compared with CK treatment,there was no significant difference in yield among WN₂₄₀,WN₂₁₀and WN₁₈₀treatments,but nitrogen application and the irrigation amount decreased by 11.11%～33.33%and 41.37%～46.25%,respectively.（5）Under the condition of water and fertilizer integration of micro-sprinkler irrigation,reducing nitrogen fertilizer application could improve the nitrogen use efficiency of maize effectively.Compared with high nitrogen treatment(WN₂₄₀),the WUE of maize under WN₁₈₀treatment had no significant change,but NPFP and NUE significantly increased by25.71%～27.45%and 6.27%～13.93%,respectively.Compared with CK treatment,the water and nitrogen use efficiency of WN₂₄₀,WN₂₁₀and WN₁₈₀treatments under micro-sprinkler irrigation increased.Among them,the WUE,NPFP,NAE and NUE of WN180 treatment increased by 5.78%～6.59%,49.23%～54.71%,45.08%～108.33%and 71.37%～72.10%,respectively.（6）Comprehensively considering the nitrogen application rate,irrigation amount,grain yield,water-nitrogen use efficiency of summer maize,it is suggested that the water and nitrogen application scheme under the micro-sprinkler irrigation in the test area as follow:the target soil layer was 0-20 cm,the nitrogen application rate is 180 kg/hm~2.The supplemental irrigation and nitrogen fertilizer was applied at the sowing and the beginning of jointing,big trumpet stage and silking stage and the nitrogen application ratio was 1:2:5:2.The target water content of supplemental irrigation is field capacity.