Research On The Optimization Management Model Of Water And Nitrogen Under Mulched Drip Irrigation For Maize In The West Of Heilongjiang

Maize is an important food crop,which is vital to food security in China.Heilongjian g Province is the largest grain base in China with 1/9 of the country's total cultivated lan d and the grain output ranks first.However,the total amount of water resources in Heilon gjiang Province is relatively scarce,and the irrigation water consumption of food crop is i ncreasing.Meanwhile,long term unreasonable nitrogen fertilizer application has caused nitr ogen loss and serious agricultural non-point source pollution.The optimum pattern of maiz e field water-fertilizer management would be established to ensure regional food security,r educe the waste of water and fertilizer resources and alleviate agricultural pollution.This experiment was conducted at the water conservancy scientific experimental station of Zhaozhou country,Heilongjiang Province.The field test and ¹⁵N tracers was adopted with two-factor of irrigation and nitrogen fertilizer application.Three irrigation levels?15,30 and 45 mm?and four nitrogen fertilizer levels?0,180,220 and 260 kg/hm²?were used t o explore the water consumption regulation,yield and water use efficiency of Maize in va rious growth stages under different water and nitrogen management.Meanwhile,¹⁵N labele d fertilizer nitrogen was used to assess the absorption,distribution and utilization of nitrog en fertilizer.The leaf senescence of maize was fitted by using logistic equation.The date of onset of leaf senescence,maximum rate of decrease in relative green leaf area,mean ra te of decrease in relative green leaf area,the day of maximum rate of decrease in relative green leaf area and nitrogen remobilization efficiency were calculated.The main research results obtained by the experiment are as follows:?1?The water consumption in jointing stage and silking stage of maize was largest,a ccounting for 52.82%to 61.39%of water consumption during the whole growth period,fol lowed by seeding stage and filling stage,accounting for 32.28%to 39.00%.The maturity stage has the least water consumption,only accounting for 6.10%to 9.88%during the wh ole growth period.The dry matter and yield has the same trend in the mature stage.Whe n the irrigation amount was low,the dry matter and yield of maize both increased first an d then decreased with the increasing of nitrogen application rate.At the medium and high irrigation amount,they both increased with the increasing of nitrogen application rate.Wat er use efficiency is affected by water consumption and yield.Under the condition of medi um irrigation,the water use efficiency was significantly increased compared with low and high irrigation volume.?2?Under different water and fertilizer conditions,the nitrogen absorbed by maize fro m fertilizer and soil accounting for 26.29%?41.08%and 58.92%?73.71%of the total nitrog en,respectively.It indicated that soil is the main nitrogen source of maize.Different organ s had different competitive ability to fertilizer nitrogen,which was shown as:grain>leaf>stem.The amount of nitrogen absorbed by the grain from fertilizers was the 2.39 to 4.75 times that of the stem and the 1.95 to 3.94 times that of the leaf.All treatments had positive excitation effect on soil nitrogen.Increasing the amount of nitrogen application co uld properly improve the absorption capacity of maize to nitrogen from soil,but when exc essive nitrogen was applied,it is necessary to increase the irrigation water to make the m aize absorbed more nitrogen from the soil.Increasing the amount of nitrogen application c ould increase the residue amount of fertilizer nitrogen in 0?60 cm soil layer.More irrigati on will move down the residual nitrogen in the surface layer.The nitrogen fertilizer loss r ate under each treatment was 21.31%?54.89%.?3?The date of onset of leaf senescence under each treatment occurred about 10 days after silking,and was less affected by irrigation and nitrogen application.Under sufficient irrigation conditions,increasing nitrogen application could reduce maximum rate of decreas e in relative green leaf area and prolong the day of maximum rate of decrease in relative green leaf area.With the same amount of nitrogen application,leaf nitrogen accumulation i ncreased first and then decreased with the increase of irrigation at silking stage.The grain filling rate changing with the trend of slow,fast and eventually to be gentle.The grain fil ling rate reached the maximum value at 30?40 days after silking.Delaying leaf senescence rate could improve the quality of 100 grains and the efficiency of nitrogen transfer in lea ves.The transport amount of soil nitrogen in all treatments was higher than that of fertiliz er.The transport amount of soil nitrogen accounted for 54.78%to 71.18%of the total tran sport amount.The contribution rate of corn stem to grain was higher than that of leaf,wh ich was 23.76%to 33.87%and 7.76%to 23.19%respectively.In summary,the irrigation water quantity of 30 mm with the nitrogen fertilizer of 260kg/hm² is the most suitable water and fertilizer management in western region of Heilongji ang Province.Under this condition,the nitrogen absorption of kernel accounts for 68.28%of the total nitrogen absorption of maize with the lowest nitrogen loss rate at 21.31%.The contribution rate of nitrogen from various organs to grains also reach the highest level,the maize yield and water use efficiency are 14267.90 kg/hm²and 3.35 kg/m³,respectively.At t he same time,the maximum rate of decrease in relative green leaf area is 1.7875 which o ccurs at 48.90 days after silking,effectively delayed leaf senescence and improved leaf nitr ogen transport efficiency.Also,the soil"nitrogen pool"is in equilibrium,and effectively r educe the leaching loss of fertilizer nitrogen with water-saving,yield increasing and emissi on reduction.