| Nitrogen fertilizer is often called "head fertilizer" by farmers.During the pragmatic fertilization process,unscientific fertilization,irrigation restrictions,ammonium volatilization losses,nitrate leaching and denitrification caused the low utilization rate of nitrogen fertilizer.irrigation amount,fertilizer amount and water-fertilizer supply mode are the key factors to determine the migration,transformation and leaching of urea nitrogen in soil.The amount of nitrogen leaching increased with the increase of irrigation amount,drip fertigation can evidently reduce the migration transformation and enrichment of nitrogen in apple orchard,so as to reduce the loss of nitrogen,improve the utilization rate of nitrogen fertilizer.Compared with the traditional drip fertigation,root zone fertigation evidently decreased the leaching loss of nitrogen.In the root zone fertigation techniques,fertilizer is transported to the roots of crops for crop uptake and utilization through drip irrigation system,overcome the shortages of the separation of traditional irrigation and fertilization,fertilization is uniformly applied to the root zone of crops,thereby increasing the absorption of crop fertilizer.In this study,a series of studies were conducted on the nitrogen use efficiency of the aerial part of hilly apple trees from three aspects: drip irrigation,nitrogen amount and irrigation amount.The main conclusions are as follows:(1)Compared with traditional irrigation,root zone drip irrigation can evidently improve the Ndff of branches and fruits,increase the absorption ability of nitrogen fertilizer in the same year by branches and fruits.Compared with the traditional drip irrigation,root zone drip irrigation can significantly improve the utilization ratio of nitrogen under the premise of water saving.However,traditional drip irrigation can increase the nitrogen content in branches and fruits compared with root zone drip irrigation,making their nitrogen content reach 1.228% and3.35%.(2)In the root zone drip irrigation treatment,when the nitrogen application rates were maintained,the nitrogen use efficiency of aerial part of hilly apple trees decreased with the increase of irrigation amount.At the same time,the different irrigation levels had a significant influence on the nitrogen content of organs.When the water amount was moderate,the suitable water could promote the absorption of nitrogen by organs,and the nitrogen content ofthe organs on the ground reached the best.In the aerial organs,the ability of storing nitrogen is the blade,followed by the branches,and finally the fruits.In fruit mature period,nitrogen nutrition mainly supply the growth and maturity of fruits,the fruit has become the most important nitrogen pool of15 N at that time.(3)In the root zone drip irrigation treatment,when the irrigation application rates were maintained,the nitrogen use efficiency of aerial part of hilly apple trees decreased with the increase of nitrogen fertilizer rate.At the same time,the nitrogen content of the branches,leaves and fruits increased with the increase of nitrogen fertilizer rate,which showed that it decreased first and then increased,indicating that only proper nitrogen conditions could promote the growth of various organs.Fruits have the best ability of absorbing and requisitioning of nitrogen fertilizer among all the organ on the ground.To sum up,In the study of drip fertigation in root zone,under suitable water condition,the rate of nitrogen fertilizer utilization under low fertilizer model was higher than that of high fertilizer model;In the suitable nitrogen environment,the utilization rate of nitrogen in low water mode was higher than that in high water model.When apple trees were treated with W2N1 under the root zone drip irrigation,the utilization level of nitrogen on the ground organs was the highest,reaching20.923%,that indicated that this treatment level was the optimum combination of water and nitrogen under the root zone drip irrigation treatments for the hilly apple of Northern Shaanxi. |
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