Study On Soil Environmental Effects Of Apple Orchard Root Zone Under Different Water And Nitrogen Coupling Conditions

According to the analysis of the current situation of agricultural development in China,the irrational fertilization and irrigation habits of farmers are the key reasons for the formation of the phenomenon of low agricultural water and fertilizer utilization.With a large number of research advances involving the rational planning of irrigation and fertilizer application schemes under water deficit constraints so as to improve resource utilization efficiency coming into view,the importance of the coupling effect of water and nitrogen on crop cultivation is receiving wide attention from more and more scholars.In this paper,based on high-frequency moisture measurement and water and nitrogen reduction on soil environment and water and nitrogen utilization efficiency in orchards,we studied the effects of different water and nitrogen coupling patterns on soil temperature,nitrogen content,microorganisms,enzyme activity,as well as tree fruit yield and water and nitrogen utilization efficiency,using 5-yearold Fuji apple park fruit trees as test materials and designing field plot trials,based on the customary production and management patterns of fruit farmers around the test area as controls.The results showed that:1.Under the same water condition,high nitrogen treatment effectively increased soil temperature.Under the same nitrogen application level,high water gradient reduced soil temperature in summer,but increased soil temperature in winter.Different water and nitrogen treatments played a certain buffer effect on soil temperature.2.Under the premise of consistent soil moisture gradient,the total nitrogen content of soil will increase with the increase of nitrogen application level.Under the premise of the same nitrogen application level,the total nitrogen content of the soil will increase with the decrease of water content.It is worth noting that compared with different water treatments,soil total nitrogen content was more significantly affected by different nitrogen application rates.After comparing different nitrogen application levels,it can be found that the distribution of soil ammonium nitrogen and nitrate nitrogen content from shallow to deep soil showed a trend of increasing first and then decreasing.With the increase of nitrogen application level,the content of ammonium nitrogen in soil increased significantly,which was mainly reflected in the 20-80 cm soil layer.In contrast,the content of soil nitrate nitrogen showed an increase with the increase of nitrogen application level,and then decreased with the increase of nitrogen application level.It is worth noting that too high levels of nitrogen application can not increase the content of nitrate nitrogen in the soil.Through the overall analysis of soil nitrogen content,it was found that W2N2 and W3N1 performed better.3.Under a certain water gradient,with the increase of nitrogen application rate,the contents of organic matter,available phosphorus and available potassium in most water and nitrogen coupling treatments increased.Under a certain amount of nitrogen fertilizer,the content of organic matter,available phosphorus and available potassium in soil decreased with the increase of soil moisture gradient.It was found that the soil nutrient content of W3N1 water and fertilizer coupling treatment was higher.4.At the fungal level,the Shannon index of W3N1 treatment was 5.660,which was higher than that of other 9 treatments,and the Simpson index was 0.948,which was also higher than that of other treatments.At the bacterial level,the Shannon index of W3N2 treatment was9.705,which was higher than the other nine treatments,and the Simpson index was 0.997,which was the same as W3N3 and also higher than other treatments,with higher bacterial community diversity.5.Under the condition of infiltration irrigation,different water and nitrogen coupling treatments could improve the enzyme activity of rhizosphere soil,and the effect of W3N3 treatment was the most obvious.The activities of urease,catalase,invertase and phosphatase were significantly higher than those of the control.Followed by W1N2,W3N2 is relatively low,indicating that the effect of different water and nitrogen coupling treatments on soil enzyme activity may be mainly achieved by affecting the number of soil microorganisms.6.In terms of yield,under the same nitrogen application rate,the apple yield of W1 treatment was significantly higher than that of W3 treatment,but not significantly different from that of W2.Under the soil moisture gradient of W1,the yield of N2 was higher than that of N1 treatment.Under the condition of water and nitrogen coupling,the maximum yield of apple was W1N2 treatment,and the minimum yield was W3N3.Under the same nitrogen application rate,the NPFP of W1 treatment was higher than that of W3 treatment.Under the condition of a certain soil moisture content gradient,the NPFP of N3 treatment was higher than that of N1 and N2 treatments,indicating that a moderate reduction of nitrogen application rate was beneficial to increase the NPFP of fruit trees.Under the condition of water and nitrogen coupling,the NPFP of W1N3 treatment was the largest,and the NPFP of W1N1 treatment was the smallest.Under the condition of certain nitrogen application rate,IWUE of W3 treatment was higher than that of W1 and W2 treatments.The IWUE of W3N1 treatment was the largest,and the IWUE of W1N3 treatment was the smallest,indicating that too high soil moisture content was not conducive to improving the irrigation water use efficiency of fruit trees.