Effects Of Long-term Fertilization On Walnut Quality And Rhizosphere Soil Microbial And Enzyme Activities

In view of the problems of soil compaction and walnut yield and quality reduction caused by unreasonable fertilization in walnut production,this study took nine-year-old’Xiangling’walnut as the research object and set up five fertilization treatments:（1）No fertilizer（CK）,（2）chemical fertilizer alone（NPK）,（3）chemical fertilizer+organic fertilizer（NPKM）,（4）chemical fertilizer+biological fungal fertilizer（NPKBO）,（5）chemical fertilizer+organic fertilizer+biological fungal fertilizer（NPKMBO）,To study the effects of long-term fertilization on walnut quality,rhizosphere soil nutrients,p H,microbial biomass carbon and nitrogen,microbial number,microbial functional diversity and enzyme activities,etc.,to clarify the optimal fertilization program,and provide theoretical basis for rational fertilization of walnut in Shanyang county and similar areas.The main results are as follows:（1）Long-term different fertilization treatments significantly increased the nutrient contents of walnut rhizosphere and bulk soil,and the nutrient contents of walnut rhizosphere soil were generally higher than that of bulk soil.The contents of SOM and TN in rhizosphere soil under NPKMBO treatment were 12.06 g·kg^-1and 2.09 g·kg^-1,respectively.Under NPK treatment,the contents of AP,NO₃^--N and NH₄⁺-N in rhizosphere soil were 105.19 mg·kg^-1,12.63 mg·kg^-1and 6.57 mg·kg^-1,respectively.（2）Long-term fertilization significantly increased the contents of SMBC and SMBN in walnut rhizosphere and bulk soil,and the contents of SMBC and SMBN in walnut rhizosphere soil were higher than those in bulk soil,and the values of SMBC and SMBN in walnut rhizosphere soil were 184.77 mg·kg^-1and 95.37 mg·kg^-1,respectively,under NPKMBO treatment.The number and enzyme activity of microorganisms in rhizosphere soil were higher than those in bulk soil.NPK,NPKM,NPKBO and NPKMBO treatments significantly increased the activities ofβG,CBH and NAG,and reached the maximum values of 300.26 nmol·g^-1·h^-1under NPKMBO treatment,respectively.84.67 nmol·g^-1·h^-1and 74.58 nmol·g^-1·h^-1;The mean color change rate（AWCD）of rhizosphere and bulk soil increased with the increase of organic matter input.（3）The yield of walnut under different fertilization treatments increased year by year with the extension of years,and the fertilization treatments significantly affectedthe mean value of three diameters,fruit weight,kernel weight and kernel percentage of walnut,and the NPKMBO treatment was the largest.（4）The oil content,unsaturated fatty acid content,total protein content and amino acid content of walnut were significantly increased by all fertilization treatments,and the effect of NPKMBO treatment was the best.In conclusion,the combined application of the three fertilizers（chemical fertilizer+organic fertilizer+biological fungus fertilizer）significantly improved soil fertility,walnut yield and kernel quality,and was the most suitable fertilizer scheme in this study.The results can provide important theoretical support for rational fertilization in walnut production.