Effects Of Nitrogen Application On Root Growth And Nitrogen Uptake Of Potted Maize Under Drought Stress

Water and nitrogen are important factors restricting crop yield.Maize is a crop with high water and nitrogen consumption.The input amount of water and nitrogen directly affects the growth and dry matter accumulation of maize.There are few systematic studies on the law of nitrogen absorption,nitrogen absorption and water and fertilizer utilization efficiency,especially the systematic studies on potted corn under different water and fertilizer supply conditions.This study intends to elucidate the effect of water and fertilizer supply on the growth and nitrogen absorption of potted maize.Principal component analysis is used to comprehensively analyze the indicators,in order to provide a theoretical basis for the regulation and management of water and nitrogen in different growth stages of field maize.In the pot experiment of maize,two factors,water deficit and nitrogen application level,were set up in different growth stages,which were composed of five irrigation levels and four fertilization levels.20 groups of treatments were set up by completely random method.Among them,the irrigation consists of 5 treatments,namely full irrigation（SI）,water deficit at seedling stage（DS）,water deficit at jointing stage（DJ）,water deficit at grain filling stage（DF）,and water deficit at maturity stage（DM）;Nitrogen treatments consisted of 4 levels,N0:0 g N kg^-1soil,N1:0.1 g N kg^-1soil,N2:0.3 g N kg^-1soil,and N3:0.5 g N kg^-1soil.The test obtained the following research results:（1）With the advancement of the growth period,the root dry matter mass of maize gradually increased,and the increase in the jointing stage was the largest,but at the mature stage,the root dry matter mass decreased;under the same irrigation treatment,the root dry matter accumulation showed that N0>N1>N3>N2,with the increase of fertilization rate,the root dry matter accumulation increased first and then decreased.The influence of water deficit on maize root dry matter accumulation in different growth stages was as follows:DJ>DF>DS>DM.The study found that when the water deficit treatment at the jointing stage has the greatest effect on the accumulation of root dry matter.（2）The overall performance is as follows:N1>N0>N2>N3,indicating that appropriate fertilization should be adopted for maize vegetative growth,and the relationship between aboveground dry matter accumulation and nitrogen application rate is approximately an open-ended downward parabola.The effect of dry matter accumulation on water deficit in different growth stages was as follows:DJ>DF>DM>DS.Combined with the root dry matter accumulation rule,it shows that the jointing period is the critical period of water demand for maize growth,so in the management of maize growth cycle,appropriate water management should be carried out in this period.（3）After the water deficit treatment of maize in different growth stages,the effect on the nitrogen uptake of maize roots was as follows:SI>DM>DS>DF>DJ,and the root nitrogen uptake of water deficit treatment at the jointing stage was the lowest.The nitrogen uptake in the shoots of maize is inversely proportional to the nitrogen application.Different nitrogen application levels and the nitrogen uptake in the shoots of maize are as follows:N1>N2>N3>N0,indicating that the nitrogen uptake capacity of the shoots of maize is limited.An effective way to increase nitrogen uptake in the shoots of maize.The effect of water deficit in different growth stages on the nitrogen uptake in the shoots is as follows:DJ>DF>DM>DS>SI,the average nitrogen uptake of the shoots in the DJ,DF,DM and DS treatments was reduced by 6.6%compared with SI,17.6%,10.9%and 5.9%,respectively.The nitrogen absorption of N1 treatment is the largest,followed by N2 treatment.The nitrogen absorption of plants decreases with the increase of nitrogen application.（4）The maximum value of water use efficiency was DSN0 treatment,and there was a negative correlation between water use efficiency and irrigation amount.The mean value of water use efficiency under water deficit conditions in different growth stages was DS>DM>SI>DF>DJ.There was a negative correlation between the amount of nitrogen absorbed by plants and the amount of nitrogen applied.The amount of nitrogen absorbed by N1 treatment was the largest,followed by N2 treatment.The amount of nitrogen absorbed by plants decreased with the increase of the amount of nitrogen applied.The maximum apparent nitrogen use efficiency of SIN1 treatment was negatively correlated with nitrogen application rate.At the N1 level,the effect of water deficit at different growth stages on the apparent rate of nitrogen fertilizer was as follows:SI>DM>DF>DS>DJ.（5）The principal component analysis method was used to comprehensively evaluate the potted maize.SIN1 treatment ranked first,DSN1 treatment ranked second,and DMN1 treatment ranked third,indicating that the best fertilization treatment was when the nitrogen application rate was N1 level.When selecting water deficit at different growth stages,water deficit at seedling stage should be considered first,followed by water deficit at mature stage.