Effects Of Slow-Release Fertilizer On Growth Physiology,Yield,Fruit Quality And Rhizosphere Soil Microorganisms Of Walnut

The yield and area of walnut in Xinjiang are increasing,and the use of fertilizer is also increasing.Fertilizer is one of the important measures to improve the quality and efficiency of walnut,and plays an important role in the growth of fruit trees.However,in the actual production process,the production cost of chemical fertilizer is increased,the utilization rate of fertilizer is low,resulting in a large amount of fertilizer waste and serious agricultural non-point source pollution.At present,China is in the critical period of comprehensive green transformation of agriculture.It is an inevitable requirement for green and sustainable development of agriculture to promote new fertilizers such as slow-release fertilizers,increase fertilizer reduction,focus on new products and improve fertilizer utilization.In view of this,under the condition of comparison with conventional chemical fertilizer application,the special slow-release fertilizer for walnut was customized.By studying the effects of different slow-release fertilizer application rates and conventional chemical fertilizer management on walnut growth,soil nutrients,rhizosphere soil microorganisms,leaf nutrient absorption,photosynthetic physiology,morphological structure,tree yield and quality,the effects of slow-release fertilizer on walnut tree growth and biological characteristics were analyzed compared with conventional chemical fertilizer management,which provided theoretical basis and technical support for the realization of the national goal of"reducing fertilizer and increasing efficiency."The main conclusions are as follows:（1）Compared with conventional fertilizer application,slow-release fertilizer can maintain soil nutrients at a certain level and reduce fertilizer loss.Compared with CK,the contents of alkali-hydrolyzable nitrogen and available phosphorus in 20～40 cm soil layer of slow-release fertilizer 1000 g·plant^-1 treatment were significantly higher than those of CK,while the content of alkali-hydrolyzable nitrogen in 40～60 cm soil layer was significantly lower than that of CK.The contents of alkali-hydrolyzable nitrogen and available potassium in 40～60 cm soil layer of CK were higher than those of slow-release fertilizer treatment group.The alkali-hydrolyzable nitrogen in 40～60 cm soil layer of CK in oil conversion period was 93.48 mg·kg^-1,which was 88.80%,80.67%,81.44%and 85.83%higher than that of slow-release fertilizer treatment,respectively.The nutrient infiltration rate was significantly higher than that of other treatments.（2）After 150 days of fertilization,the Chao1 index and Shannon index of bacterial community and fungal community in non-rhizosphere soil treated with slow-release fertilizer 600 g·plant^-1 were significantly higher than those of CK.The application of slow-release fertilizer increased the relative abundance of Acidobacteria,Verrucomicrobia and Latescibacteria in rhizosphere soil.The relative index and species of Zoopagomycota,Chytridiomycota and Rozellomycota in soil were increased.It shows that slow-release fertilizer management can improve the diversity of bacteria and fungi in walnut non-rhizosphere soil and increase the species of soil fungi.（3）There was no significant difference in chlorophyll content of walnut leaves between 600 g·plant^-1treatment,1000 g·plant^-1 treatment and CK from expansion period to maturity period.Compared with conventional chemical fertilizer application,the leaf area and perimeter of 1000 g·plant^-1 slow-release fertilizer treatment were significantly higher than that of CK from expansion period to oil conversion period.The application of slow-release fertilizer could improve the net photosynthetic rate of walnut leaves.The net photosynthetic rate of leaves treated with slow-release fertilizer 1000 g·plant^-1 in the expansion period was significantly increased by 22.61%compared with CK,and the net photosynthetic rate of leaves treated with slow-release fertilizer 800 g·plant^-1 in the oil conversion period and mature period was significantly increased by 16.62%and 18.67%compared with CK.The slow-release fertilizer treatment can maintain the nutrients of walnut leaves at a certain level.The contents of nitrogen,calcium,magnesium,iron and zinc in the leaves of the slow-release fertilizer 1000 g·plant^-1 treatment were significantly higher than those of CK,which were1.04,1.19,1.18,1.55 and 1.14 times of CK,respectively.There was no significant difference in phosphorus and potassium content between each treatment and CK at mature stage.（4）Compared with CK,the amount of slow-release fertilizer decreased by 76.74%,65.12%,53.49%and41.86%respectively,but the yield per plant and fruit quality of walnut did not decrease.Compared with CK,the single fruit weight and kernel weight of walnut fruit were significantly reduced by 14.87%and 11.80%respectively,but the single fruit weight was significantly increased by 3.75%,the reducing sugar content was significantly increased by 31.71%,and the yield per mu was significantly increased by 33.93%.Under the application of 400 g·plant^-1 slow-release fertilizer,the yield per plant of walnut was significantly reduced by 4.22%compared with CK,while the single fruit weight and kernel weight were significantly reduced by5.93%and 8.34%,respectively.Under the application of 800 g·plant^-1 slow-release fertilizer,the kernel rate of walnut fruit was significantly reduced by 5.19%compared with CK,but the cellulose was significantly increased by 46.67%,and the yield per plant was increased by 2.04%,the difference was not significant.