Effects of Peanut Meal Enzymatic Optimization Process and its Products Replacing some Nitrogen Fertilizers on Potato Growth and Soil Environment

Abstract

Background: *Peanut meal is rich in proteins and minerals, and is commonly used in traditional agriculture for direct return to the field or compost fermentation and then applied. However, compost fermentation not only takes a long time and the products are unstable, but also tends to attract pathogens. Soil application of organic fertilizer is an effective method to maintain high crop yield and sustainable soil fertility. In this study, a 4-factor, 3-level Box-Behnken Design test was designed to optimize the process of alkaline protease hydrolysis of peanut meal, and used to prepare the enzymatic solution, and compared with the fermentation solution fermented by the traditional process, to evaluate the effects of both on potato growth and soil environment by replacing 5%, 10%, 15%, and 20% nitrogenous fertilizer under field conditions. Results: The Box-Behnken Design test showed that the optimum reaction conditions for alkaline protease hydrolysis of peanut meal were: reaction time of 4 h, initial reaction pH 9.0, reaction temperature of 55 ℃, and enzyme addition of 800 U·kg^− 1. The total nitrogen content of peanut meal after enzymatic hydrolysis was 5.10 g·kg^− 1, which was much higher than that of the peanut meal fermentation broth obtained from traditional fermentation (N 1.80 g·kg^− 1). The field experiment showed that the enzyme solution replacing 10% nitrogen fertilizer had the greatest increase in potato yield, which was 26.63% and 12.22% higher than that of the control group and the fermentation solution treatment group, respectively; in addition, the enzyme solution replacing nitrogen fertilizer could increase the nitrogen, phosphorus, potassium and dry matter content of potato tuber, and at the same time, it could effectively improve the physical and chemical properties of the soil, increase the diversity of the soil bacterial species in the rhizosphere, and change the structure of the bacterial community. Conclusions: The above results show that alkaline protease hydrolysis of peanut meal can greatly shorten the hydrolysis time of peanut meal and increase the nutrient content of the hydrolysate, which promotes the efficient use of peanut meal resources. The use of enzymatic hydrolysis solution to replace part of nitrogen fertilizer can not only reduce the use of chemical fertilizer, but also improve potato yield and quality, and improve the soil environment.