Relationship Between Water Content,Soil Nitrogen,Yield And Quality Of Maize In Trace Irrigation And Optimization Of Irrigation Schedule

Trace irrigation is a new kind of subsurface drip irrigation,which can supply water slowly and continuous to the root zone of crops.For this irrigation mode,how to get its irrigation schedule and irrigation mode is particularly important.This irrigation method does not affect crop growth,and is very important for the popularization and application of this technology.In this paper,The physiological growth index of maize is analyzed by trace irrigation.And the effects of trace irrigation on water and nitrogen transport are studied.The effects of different pressure water head and fertilizer amount on maize root system,yield and quality,and the optimization of irrigation system based on RZWQM model are studied.The following results are obtained:(1)Try to measure the plant height,plant diameter,dry matter and photosynthetic rate of maize under trace irrigation,it can be seen that under the trace irrigation,difference of plant height is gradually obvious in the treatment during the growth period,and apply base fertilizer,and then supply topdressing fertilizer at a ratio of 0:5:5 is the highest before August 10th,and later normal subsurface drip irrigation treatment exceeds the apply base fertilizer,and then supply topdressing fertilizer at a ratio of 0:5:5.There is no obvious difference in plant height.From the point of dry matter accumulation,there is no significant difference between the treatments before September 20th(before the booting stage),and then after September 20th,each treatments have great difference.The apply base fertilizer,and then supply topdressing fertilizer at a ratio of 0:5:5 could increase the accumulation of dry matter in the tasseling stage period of maize,and the rest treatment has a certain effect of inhibitory action on reproductive growth.(2)By analyze the soil moisture,soil matrix potential,soil nitrogen transport,nitrogen accumulation and nitrogen utilization ratio in trace irrigation,It can be seen that water mainly affect the soil water in the vertical 35 cm depth,in the continuous irrigation method.Continuous irrigation increased water content at the emitter position.Pulse irrigation has lower water content at the emitter position,which may be due to the large flow,allowing for water penetration into the deeper soil layer.From different fertilization treatment,It is find that not apply base fertilizer,and then supply topdressing fertilizer at a ratio of 2:4:4 and apply base fertilizer,and then supply topdressing fertilizer at a ratio of 0:5:5 treatments are closer in nitrogen transport,which is beneficial to the absorption of nitrogen by roots,and reduce the deep leakage caused by the deep transport of nitrogen.The suitable head pressure is 2m,and water is slowly supplied to com under this water head.The suitable irrigation matrix potential range is-30--60kPa.In the North China Plain,the rainfall is about 280mm during the growth period,and the total irrigation amount is about 80mm.taking account of the migration and transformation of ammonium nitrogen and nitrate nitrogen,and not apply base fertilizer,and then supply topdressing fertilizer at a ratio of 2:4:4 in the seedling stage,jointing stage and tasseling stage,respectively,is not only beneficial to the uptake and utilization of nitrogen by roots especially in the 20-35 cm soil depth,but also more conducive to the development of crop roots.(3)Through the comprehensive analyze of hydrogen and oxygen isotopes,maize roots,yield and quality under trace irrigation;It can seen that in terms of the root distribution,continuous irrigation increased root growth in the early period of maize,namely,seedling and jointing stages of growth periods.Root growth of the normal subsurface drip irrigation treatment in this period under the condition of pulse irrigation is relatively slow.The pulse irrigation increase the root development at the tasseling and booting stages because of certain water stress.The development is stronger in the deep layer at the tasseling stage.In the mature stage,no apply base fertilizer,and then supply topdressing fertilizer at a ratio of 0:5:5 treatment has stronger root development in the surface layer,while not apply base fertilizer,and then supply topdressing fertilizer at a ratio of 2:4:4 has stronger root development in the deep layer.The root system mainly utilize water and fertilizer in the 0-20cm soil layer at the seedling stage.The water and fertilizer mainly absorb 20-40cm in the later jointing stage.The grain filling stage absorb 40-80cm water and fertilizer.Trace irrigation makes the root water absorption depth of maize increase in shallow layer in the early growth stage,and in the middle growth stage,water absorption depth increases in the deep layer,but there is no difference between the depth of water absorption in the later growth stage compare with ordinary subsurface drip irrigation.Under the condition of 2m-5m irrigation head,the comprehensive index of yield and quality is the highest underthe condition of trace irrigation.Therefore,the recommended irrigation is 2-5m trace irrigation.From the effect of fertilizer application on yield and quality of maize,it is found that under the condition of 0.5N-0.75N,the comprehensive index of yield and quality is the highest.(4)After calibrating.and validating of the RZWQM model by the parameters of soil moisture content,soil water storage,plant height,leaf area,dry matter and soil nitrogen.The results show that the fitting effect is better.The model could simulate soil moisture content,soil water storage,crop parameters and nitrogen conversion parameters.The water simulation of three hydro logical years shows that surface water content is greatly influenced by irrigation and rainfall,and the water content in deep soil is less affected by rainfall and irrigation,and the trend is slowly decreasing.In terms of comprehensive water and nitrogen use efficiency,nitrogen application rate of 120kgN/hm2 is more favorable for crop growth.Too much nitrogen applications are not increase crop yield.The nitrogen use efficiency of each hydro logical year decreased significantly with the increase of nitrogen application,and the hydro logical year precipitation has a significant effect on nitrogen leakage in maize.