Coupling Effect Of Water And Nitrogen On Maize Grown,Nitrogen Use Efficiency And Root Spatial Distribution Of Spring Maize During The Seeding Stage

Northeast China is an important production base of maize,planting area and yield accounted for 31.6% and 34.5% of the country respectively in 2015,due to the natural rainfall in northeast spring maize production is the main source of soil moisture,so drought caused by lack of precipitation is the primary ecological stress factor affecting the production of spring maize,in many parts of the world,drought severely limits production.Effects of nitrogen application and irrigation on growth and yield of spring maize were significantly promoted,however,the effects of water and nitrogen on the growth and root distribution of spring maize and their coupling effects were seldom studied,in this project,pot experiments were conducted for four moisture gradient simulating field conditions of severe drought,mild drought,moderate moisture and excess moisture(relative soil water content of 30%,50%,70% and 90% as W0,W1,W2 and W3),and three nitrogen(0,0.12,0.24 g N/ kg dry soil as N0,N1,N2),3D-Monolith root sampling were used for investigating the spring maize responses to different water and nitrogen management practice in terms of maize grown,nitrogen use efficiency and root spatial distribution,to evaluate the coupling effects of water and nitrogen on maize grown,nitrogen use efficiency and root spatial distribution,the following results are obtained:(1)Water and nitrogen significantly affected the growth and nitrogen uptake of maize,nitrogen deficiency and drought treatment is the worst on grown,plant height,stem diameter,leaf number,SPAD were 60.4cm,19.7mm,5.5 and 28.8;as the soil moisture and nitrogen fertilizer increased,the indexes showed an upward trend;plant dry weight and nitrogen uptake increased with the increase of water and nitrogen application rate,nitrogen treatment was significantly higher than the treatment without nitrogen application,under the W2 condition,the nitrogen application rate of dry weight was the most significant,and the N1 and N2 treatment increased by 131.4% and 116.6%,respectively;the nitrogen use efficiency,N1 treatment were higher than those in treatment N2;under the condition of different nitrogen supply,nitrogen recovery efficiency and agronomic efficiency of water treatment were consistent,all showed W2 > W3 > W1 > W0.(2)Under the same water condition,N0 treatment root length and root dry weight were mainly distributed in lower layers of the soil,W0 and W1 treatment half layer of root length occupy most total root length of 60% and 60.9%,it is two times the proportion of root length;under the condition of W0,maize total root length and total surface area of N0 treatment were the largest of 1220.5m and 75m2 respectively,and decreased gradually with the increase of nitrogen content,the total root dry weight and total volume of N1 treatment were the highest under the W0 and W1 condition.Under W2 and W3 condition every index of N0 treatment was significantly lower than that of N1 treatment and N2 treatment.The results showed that drought and nitrogen deficiency promoted maize root elongation and increased total root length and total surface area.(3)Under the same water condition,maize root length density,surface area density and dry weight density of N0 treatment in the soil on the surface layer of the longitudinal distribution of the number and proportion were significantly less than that of N1 treatment,N2 treatment,and the number and distribution proportion in middle and lower layers is significantly higher,and the horizontal distribution is relatively more balanced.Especially under the condition of W0 and W1,the increase of root length under nitrogen deficiency treatment was more obvious in the deep soil layer,and the root length of enough water and nitrogen treatment was more obvious in the surface layer.It can be seen that under the condition of drought,the appropriate amount of nitrogen application or the increase of soil moisture can promote the growth and development of maize.It is recommended that the W2N1 combination is the optimal in the experiment,In the actual production,the coupling effect of water and nitrogen should be taken into account,considering the application of water and nitrogen fertilizer,the yield could be increased further.