Study On Water-nitrogen Coupling And Its Threshold For Maintaining Stable Crop Growth In Saline Irrigated Areas

Hetao irrigation area in Inner Mongolia is located in the middle and upper reaches of the Yellow River.It is one of the three irrigation areas in China and the most important grain base in north China.As one of the most important grain crops in hetao irrigated area,the planting area proportion of corn reached 14.5%.At present,many scholars at home and abroad have obtained many fruitful results on the coupling effect mechanism of water and fertilizer.The coupling mechanism of water and fertilizer is more complex under the condition of maintaining the stable growth of farmland crops.In recent years,a series of ecological environmental pollution and resource waste problems caused by unreasonable water and nitrogen coupling model not only affect the stability of farmland ecosystem,but also hinder the development of"environmentally friendly" and "resource-saving" agriculture in hetao irrigated areas.Based on the results of previous studies on the coupling of water and fertilizer in salinized soil in hetao irrigated area,this paper studies a reasonable coupling scheme of water and nitrogen under the premise of stable crop growth,which is of great significance to the rational development and utilization of water and soil resources,sustainable development of regional agriculture and ecological protection in hetao irrigated area.In this paper,the main grain crop maize in hetao irrigation area is taken as the research object,and the key factors affecting the stability of salinized farmland crops are discussed by field experiment and statistical analysis,and the corresponding response model is established,and the threshold value of the key factors is obtained.The main research contents and conclusions are as follows:(1)multiple interconnected by principal component analysis(pca)will affect maize growth factors into a few unrelated comprehensive index,determined by the size of the cumulative contribution rate of the number of principal components,and then determine the key elements which influence the stability of maintaining maize growth for irrigation water and fertilizer(contributed more than 80%).At the same time,the method of redundancy analysis is used to verify it.(2)through the establishment of a model of water and nitrogen yield,regression analysis was carried out with dimensionless independent variables of irrigation amount and fertilizer application amount and the yield of dependent variable,and the degree of influence of irrigation amount and fertilizer application amount on the yield of dependent variable was judged by the regression coefficient.Principal component analysis was used to determine the importance of the two factors,and then single-factor analysis was used to determine the size of the optimal threshold of each factor.(3)the combination of historical literature test results and the measured data,analysis of maize physiological character,soil moisture content,nitrate nitrogen,ammonium nitrogen,the change of the yield and its components,are preliminary salinization area suitable for maize growth,namely protect corn production under the premise of maize growth basic reaches stable irrigation water and fertilizer,the dosage of irrigation water in 150?175 m3/mu,fertilizer rate in 25?29 kg/mu.