The Effect Of Water And Nitrogen Interaction On The Maize Leaves Physiological Function,Utilization Of Fertilizer And Water And Yield In The Middle Hilly Area Of Sichuan Province

Water and nitrogen are two important factors that impact crop growth and yield formation,there are significant interaction effects between them.Drip irrigation water and fertilizer integration is the most advanced water and fertilizer management method in the world,which can promote fertilizer by water,adjust water by fertilizer,exert the synergetic and coupling effects of water and fertilizer,so as to improve crop yield and fertilizer and water utilization efficiency.The hilly region of central Sichuan is the main corn producing area of Sichuan province,excessive application of nitrogen fertilizer and frequent seasonal drought are the main problems in maize production,rainwater harvesting、supplementary irrigation and nitrogen reduction are the direction of green development.So,in this paper,we set up two factor tests with different nitrogen levels and drip irrigation quantity,factor A was nitrogen application rate(nitrogen reduction of 25%N₁₈₀and total nitrogen N₂₄₀),factor B was drip irrigation quantity,（set non-drip irrigation B₀,drip irrigation 375m³/hm²B₁,drip irrigation 750 m³/hm²B₂,drip irrigation 1125 m³/hm²B₃）,and no nitrogen application and no drip irrigation were used as control（N₀）.We researched the effects of water and nitrogen interaction on soil physical and chemical properties,leaf physiological function,water and fertilizer absorption and utilization,material accumulation and distribution,and yield composition.In order to provide the theoretical basis for the reasonable fertilizer and water management of maize in this area.The main results were as follows:1.Increase nitrogen application could promote the growth of maize and increase plant height,stem diameter and leaf area index in silking stage.With the increase of drip irrigation amount,stem diameter and LAI in silking stage increased,and the effect of irrigation on increasing LAI under nitrogen reduction(N₁₈₀)was greater than that of total nitrogen(N₂₄₀).2.Increase nitrogen application could increase the dry matter rate and accumulation in each period,and to a certain extent increased the grain distribution,namely the harvest index.On the average of two years,the accumulation of dry matter per plant in big trumpet,silking and maturity stage of N₁₈₀and N₂₄₀were 18.9%and 54.6%、22.8%and 42.2,26.4%and 48.9%higher than N₀.With the increase of irrigation amount,the dry matter accumulation rate and amount in each period also increased in different degrees,there were some differences in the amplitude between different nitrogen levels,and irrigation had a greater effect under the condition of nitrogen reduction.There was no significant difference between N₁₈₀B₃and N₂₄₀B₀in dry matter accumulation.3.The interaction of water and nitrogen could delay the senescence of maize leaves and maintain the balance of carbon and nitrogen metabolism.Increased nitrogen application and appropriate drip irrigation were beneficial to increase chlorophyll content,activity of SOD,CAT,POD and other antioxidant enzymes and SPS,SS and GS carbon and nitrogen metabolizing enzymes,reduce MDA content,too.However,excessive irrigation（B₃）could lead to partial antioxidant enzyme and carbon and nitrogen metabolizing enzyme activity in some periods,reduce the physiological function of leaves,especially in normal nitrogen condition.4.With the increase of nitrogen application rate and drip irrigation amount,the nitrogen accumulation rate increased gradually in silking stage and maturity stage,and the effect of nitrogen level was greater than that of irrigation,the influence of irrigation on nitrogen reduction(N₁₈₀)was greater than that on total nitrogen(N₂₄₀),there was no significant difference in N accumulation between N₁₈₀B₃and N₂₄₀B₀.Nitrogen application increased,the agricultural utilization rate,nitrogen partial productivity,nitrogen utilization efficiency and dry matter productivity of nitrogen fertilizer were decreased,the apparent nitrogen loss and loss rate increased.With the increase of drip irrigation amount,nitrogen utilization efficiency,dry matter productivity,apparent nitrogen loss and loss reduced,the agricultural utilization and partial productivity of nitrogen fertilizer increased under the condition of nitrogen reduction(N₁₈₀),but it rised first and then fell under the condition of total nitrogen(N₂₄₀).5.In general,the moisture content of different soil layers were 10-20cm>20-30cm>0-10cm.With the increase of drip irrigation amount,the soil moisture content increased correspondingly（especially in filling stage and 10-20cm layer）,water consumption in the fields also increased,corn grain productivity per unit of water（WUE1）decreased,But the dry matter productivity（WUE2）per unit of water did not decrease much,which even increased in nitrogen reduction.The increase in nitrogen fertilizer promoted the growth of corn,increased the absorption and utilization of soil water.Therefore,there was a tendency to reduce soil moisture,but it could improve WUE.6.With the increase of nitrogen application rate and drip irrigation amount,maize ear length,ear diameter,grain number and 1000-grain weight all showed an increasing trend,and the length of bald tip decreased,yield increased to varying degrees,too.The effect of nitrogen fertilizer is greater than that of irrigation,some yield characters also had the interaction effect of nitrogen fertilizer and irrigation.With the increase of drip irrigation amount,the grain yield of maize under N₁₈₀condition increased gradually,but the total nitrogen(N₂₄₀)increased and then decreased,water and nitrogen showed some interaction and coupling synergistic effect.The yield of N₁₈₀B₂and N₁₈₀B₃were not significantly different from that of N₂₄₀B₀.High nitrogen and water could not get high yield of maize necessarily,it would increase the cost of production,reduce fertilizer and water utilization rate and economic benefit.Under the conditions of this experiment,the recommended management mode of fertilizer and water was applying 180kg/hm²with pure nitrogen,drip irrigation with 750-1125m³/hm².