Effects Of Nitrogen Application Rates On Soil Water And Fertilizer Utilization, Growth And Yield Of Spring Maize In Weibei Dryland

Water deficiency is a main limiting factor for maize growth in dryland.The seasonal fluctuation of precipitation and the frequent occurrence of drought have severely affected the normal growth and stable production of spring maize in Weibei dryland.Rational nitrogen application can promote growth,increase yield,increase benefit and alleviate adverse effects of drought.However,the phenomenon of unreasonable nitrogen application is more common in production,therefore,study on the utilization of water and fertilizer,the growth and yield of maize under natural precipitation conditions is of great significance to the rational nitrogen application of spring maize in Weibei dryland,to achieve the goal of reducing nitrogen,increasing production,increasing efficiency and promoting its sustainable development.An in–situ experiment was conducted in Heyang county located in Weibei dryland from 2016 to 2018,with five treatments of nitrogen rates between 0-360 kg N ha^-1,which were represented by N0,N1,N2,N3 and N4.The test varieties were Zhengdan 958（ZD958）and Shandan 8806（SD8806）.The effects of different precipitation and nitrogen application rates on water use,nutrient changes,maize growth,yield composition and economic benefits in spring maize fields were analyzed in this paper.The main results are as follows:（1）Effects of different nitrogen application rates on soil water use in spring maize fieldThere were two distribution types of precipitation in the test years,one was rainy at the ear stage and droughty at the grain stage（2016,2018）,while the other was droughty at the ear stage and rainy at the grain stage（2017）.The key period of maize water requirement is jointing to tasseling stage,which is helpful to meet crop growth demand and avoid soil dryness.As the growth process advanced,the soil water storage capacity of 0-200 cm soil layer in 2016,2017 and 2018 showed a trend of“rise-drop”,“drop-rise”and“drop-rise-drop”respectively.The soil water storage in the 0-40 cm soil layer changed sharply,followed by 40-80 cm,and the lowest was 160-200 cm.The drought and increased nitrogen application increased the deep water use.There was a strong correlation between the grain yield of spring maize and the precipitation from fallow to tasseling or the sum of soil water storage before sowing and precipitation from sowing to tasseling,So the grain yield could be predicted and analyzed according to this relationship.（2）Effects of different nitrogen application rates on soil nutrients in spring maize fieldThe soil nutrient content in 0-60 cm soil layer of different treatments was highest in the surface layer（0-20 cm）,and gradually decreased with the deepening of the soil layer.Increasing nitrogen application rate could increase soil total nitrogen content and the content of nitrate nitrogen in soil increased with the increase of nitrogen application rate.After the first complete growth period and fallow,the contents of soil organic matter,total nitrogen and total phosphorus were slightly lower than those before the experiment,and continued fertilization continued to increase.After harvest in 2017,it increased more than before sowing.Soil organic matter and total nitrogen in 2018 have decreased slightly after harvest in 2017.（3）Effects of different nitrogen application rates on agronomic traits,nutrient uptake and nitrogen utilization of spring maizeThe dynamics of dry matter accumulation in the upper part of spring maize showed an“S”shape,and reached the highest at maturity,and nitrogen application significantly increased the dry matter accumulation at maturity.The drought from the jointing to the tasseling period significantly reduced the amount of dry matter growth,and also reduced the harvest index.The growth and development of Shaandan8806 is better than Zhengdan958 under the condition of sufficient precipitation and high nitrogen supply.Increasing nitrogen application rate could increase leaf chlorophyll content,net photosynthetic rate and transpiration of leaf at ear position,and drought would reduce photosynthetic capacity of leaves.With the advancement of growth,the nitrogen accumulation in the aboveground part increased gradually,the nitrogen accumulation in stems and leaves increased to the highest and then decreased at tasseling stage,and grain increased rapidly.The nitrogen application significantly increased the total nitrogen accumulation at maturity,drought at ear stage significantly decreased total nitrogen uptake and grain nitrogen harvest index.The interannual nitrogen fertilizer partial productivity and nitrogen use efficiency were 2016>2018>2017,and the nitrogen uptake of 100 kg grain was 2017>2018>2016.The partial productivity of nitrogen fertilizer decreased with the increase of nitrogen application rate.The nitrogen use efficiency decreased with the increase of nitrogen application rate in 2016 and 2018,and increased first and then decreased with the increase of nitrogen application rate in 2017.Nitrogen agronomic efficiency increased first and then decreased with the increase of nitrogen application rate,and performed higher under N2.（4）Effects of different nitrogen application rates on yield,WUE,quality and economic benefits of spring maizeDrought at the ear stage significantly reduced the number of ears and kernel number per ear,while drought in the grain stage decreased kernel weight.The grain yield in 2017 was significantly lower than that of 2016 and 2018.The grain yield increased first and then decreased with the increase of nitrogen application rate,showing a quadratic parabolic trend,which was consistent with the law of decreasing returns,and the water use efficiency（WUE）performed similar to grain yield.In the case of being rainy at the ear stage and droughty at the grain stage there occurred the highest grain yield and WUE in N3,in contrast when it was droughty at the ear stage and rainy at the grain stage,spring maize performed better in N2 treatment.As a whole,the marginal product and marginal revenue increased first and then decreased with the increase of nitrogen application rate,higher under N2 treatment,and marginal cost reduced first and then increased.The effect of nitrogen application on increasing yield and income was obvious,but when the nitrogen application rate was continuously increased,the effect of increasing yield and increasing income would decrease.Increasing nitrogen application rate could increase the content of crude protein in grain,the crude fiber content increased at first and then decreased with the increase of nitrogen application rate.The crude protein content of Zhengdan958 was slightly higher than that of Shaandan8806.The content of crude fiber in the grain of Shaandan8806 was 0.3%higher than that of Zhengdan958.In the spring maize production in Weibei dryland,it can apply 150 kg N ha^-1 as basic fertilizer,then predict the yield according to“soil moisture+precipitation”,combined with the relationship between grain yield and nitrogen application rate,comprehensive utilization of nitrogen fertilizer,economic benefit,quality use and other factors,then estimate and adjust nitrogen fertilizer amount in the key period,so as to reduce nitrogen production,save cost and increase efficiency in Weibei dryland.