Effects Of Available N And Slow-Released N Fertilizer Combined With Organic Fertilizer On Physicochemical Properties Of Coastal Saline Soil And Yield Of Wheat And Maize

In order to improve the coastal saline soil,improve the productivity and economic benefits,the effects of different ratio of avaliable and slow-released nitrogen fertilizer and the amount of organic fertilizer on physicochemical properties of saline soil,yield of wheat and maize,nitrogen fertilizer use efficiency and economic benefits were studied to provide theoretical basis for the improvement of saline soil in coastal areas.In this paper,field experiments of planting two seasons of wheat and one season of maize were carried out to study the physicochemical properties,crop yield and nitrogen use efficiency of soil under the same nutrient application rate of 225 kg N hm^-2-150 kg P2O5 hm^-2-75 kg K2O hm^-2 on saline soil with different ratio of urea and control-released urea and amount of organic fertilizer without applying nitrogen fertilizer and organic fertilizer as blank.And based on the effects of crop yield,nitrogen use efficiency and net income,regression equation models were established.The main results are as follows:（1）Although,in coastal saline soil,the ratio of avaliable and slow-released nitrogen fertilizer 30%:70%and organic fertilizer 4.0 t C hm^-2 had no significant effect on soil p H,it significantly reduced the water-soluble salt content by 10.1%～12.2%and 4.8%～8.3%respectively in the wheat season and maize season compared with the CK,which effectively alleviated the salt stress of coastal saline soil.Compared with the urea combined with 1.6 t C hm^-2 organic fertilizer,the content of total nitrogen,available phosphorus,available potassium and organic matter in the topsoil was increased by 70%of controlled-release urea treatment with 4.0 t C hm^-2 organic fertilizer,which was increased by 16.5%,17.5%,1.5%and 13.7%in the wheat season,and 15.1%,11.2%,3.7%and 21.7%in the corn season,respectively.At the same time,the contents of nitrate and ammonium nitrogen in soil after wheat tillering stage and maize season were significantly increased,and the nitrate nitrogen contents in 0-20cm soil layer were increased by 59.76%and 85.00%,ammonium nitrogen contents were increased by 60.36%and 93.30%,respectively,which effectively reduced the leaching of nitrate and ammonium nitrogen in 40-100cm soil layer,nitrate nitrogen reduced by 55.4%and 62.2%on average,and47.7%,61.5%of ammonium nitrogen.（2）In this experiment,the yield components and yield of wheat and maize increased with the increase of the proportion of slow-released nitrogen fertilizer and the amount of organic fertilizer.The treatment effect of 30%:70%ratio of avaliable and slow-released nitrogen fertilizer with 4.0 t C hm^-2 organic fertilizer was the highest,which increased by 7.1%～46.8%and 9.4%～79.1%respectively compared with other treatments.The interaction between the the ratio of avaliable and slow-released nitrogen fertilizer and the amount of organic fertilizer significantly affected the grain weight and the number of panicle rows of wheat,the grain weight of maize.NAE,NPFP and NUE of wheat and maize were increased by 116.7%,34.4%,38.4%and 168.7%,60.4%,62.8%,respectively,compared with those of urea and low organic fertilizer.At the same time,the net income of wheat and maize increased with the increase of the proportion of slow-released nitrogen fertilizer,and decreased with the increase of the amount of organic fertilizer.The treatment with 70%slow-released nitrogen fertilizer and 4.0 t C hm^-2 organic fertilizer obtained the highest net income with the advantage of high yield,which increased by 0.17～1.16 times and 0.09～15.42 times respectively compared with other treatments.（3）The optimal proportion of slow effect nitrogen fertilizer with organic fertilizer application was 73.78%～75.9%with 3.75 t C hm-2～4.35 t C hm-2 in wheat season and70.56%～74.76%with 3.93 t C hm-2～4.29 t C hm-2 in corn season.Based on the relationship between yield,nitrogen use efficiency and net income of wheat and maize,the proportion of slow-released nitrogen fertilizer and the amount of organic fertilizer,a binary quadratic fitting equation was established by stepwise regression analysis.The fitting degree R² of different equations was in the range of 0.930～0.975.The optimal proportion of slow-released nitrogen fertilizer with organic fertilizer application was73.78%～75.9%with 3.75～4.35 t C hm^-2 in the wheat season and 70.56%～74.76%with3.93～4.29 t C hm^-2 in maize season.（4）In summary,the application of controlled-release urea blending ratio of 70.0%～76.0%and organic fertilizer dosage of 3.75～4.35t C hm^-2 is recommended as the most suitable amount for planting wheat and maize in coastal saline soil under the condition of nutrient application of 225 kg N hm^-2-150 kg P2O5 hm^-2-75 kg K2O hm^-2,so as to achieve improvement of yield and nitrogen fertilizer use efficiency and achieve the maximum economic benefits.