[Effects of microbial fertilizer on soil improvement and fruit quality of kiwifruit in old orchard.]

The continuous cropping obstacles caused by the increase of kiwifruit planting period resulted in imbalance of soil microbial community structure, and decrease of soil enzyme activity and physicochemical indicators, which substantially reduced both the quality and yield of kiwifruit. Under the field conditions, the traditional fertilization of fruit farmers was used as a control (CK) to study the effects of two different microbial fertilizers, JF and KF, which had been verified the growth promotion of kiwifruit aseptic seedlings test, on soil microbial community structure, soil enzyme activities, soil physicochemical characters during different growth periods of kiwifruit (germination period, florescence period, fruit enlargement period, fruit ripening period and next year germination period), as well as fruit quality. The results showed that both fertilizers significantly increased the ratio of bacteria with fungi and the ratio of actinomycetes with fungi in the kiwifruit orchard soil, indicating that they could improve and balance the soil microbial community structure. The enzymes activity in kiwifruit orchard soil with the addition of both fertilizers were significantly higher than that in CK, and among which sucrose, urease, phosphatase and polyphenol oxidase were increased by 17.9%-83.5%, 7.9%-83.0%, 7.3%-45.4% and 8.1%-140.3%, respectively. JF and KF increased soil fertility (the concentrations of available nitrogen, phosphorus, potassium, total nitrogen, total phosphorus, total potassium, and organic matter content significantly increased) and decreased soil pH (a decrease of 0.29 to 0.34). After application of microbial ferti-lizer, the content of vitamin C, soluble sugar, soluble protein and other contents of kiwifruit increased, and the titratable acid content decreased. Therefore, the application of both fertilizers could balance soil microbial community structure, enhance soil fertility, and improve the fruit quality of kiwifruit. Our results provide robust theoretical basis for the application of microbial fertilizers in the old-aged kiwifruit orchards.