Objective To optimize the enzymatic hydrolysis process of peanut meal using Box-Behnken Design, and investigate the effects of the resulting hydrolysate as a partial substitute for inorganic nitrogen fertilizer on potato growth and soil quality, aiming to promote the resource utilization of peanut meal waste and the sustainable development of potato production.

Method A 4-factor, 3-level Box-Behnken Design experimental design was used to optimize reaction time, initial pH, reaction temperature, and enzyme addition amount for preparing an enzymatic hydrolysate (M) with high protein hydrolysis efficiency. Under field conditions, the effects of M and traditionally fermented peanut meal broth (F) on potato crops and soil quality were compared at inorganic N fertilizer substitution rates of 5% (M5, F5), 10% (M10, F10), 15% (M15, F15), and 20% (M20, F20).

Result The optimal conditions for peanut meal protein hydrolysis were: Reaction time of 4.5 h, initial pH of 8.6, reaction temperature of 54.9 ℃, and enzyme addition amount of 900.8 U·g⁻¹, with an average hydrolysis degree of 25.02%. After optimization, the nutrient contents of M were: Total N 5.10 g·L⁻¹, total P 5.30 g·L⁻¹, total K 9.70 g·L⁻¹, and organic matter 50.40 g·L⁻¹. The M10 treatment exhibited the optimal effect on increasing the total potato yield and large potato production, with the total yield and large potato rate increasing by 26.63% and 30.90%, respectively; Tuber N, P, K, and dry matter content increased by 19.04%, 22.47%, 29.32%, and 31.86% higher than those of the control, respectively. For the M20 treatment, soil pH increased by 5.70%, compared with the control, while organic matter content and electrical conductivity increased by 13.48% and 40.06%, respectively. The alkaline-hydrolyzable N content reached a peak of 106.26 mg·kg⁻¹ in the M15 treatment, which was 5.7% higher than that of the control. The α diversity indices of the bacterial community in the M10 treatment were significantly higher than those in the other treatments, and the relative abundances of the plant-beneficial bacteria Terrabacter and Sphingomonas were significantly increased.

Conclusion After process optimization, both the degree of hydrolysis and nutrient content of peanut meal are improved. Replacement of 10% N fertilizer with the enzymatic hydrolysate obtained under optimal process conditions can significantly increase potato yield and quality, as well as the α diversity of bacterial communities and the relative abundance of plant-beneficial bacteria, whereas substituting 15% or 20% N fertilizer with the hydrolysate can effectively alleviate soil acidification and enhance soil fertility.