Effects of Compound Fertilizer Decrement and Water-Soluble Humic Acid Fertilizer Application on Soil Properties, Bacterial Community Structure, and Shoot Yield in Lei Bamboo (Phyllostachys praecox) Plantations in Subtropical China

Lei bamboo (Phyllostachys praecox) is an economically viable bamboo species with rich nutrition, a good taste, and a high yield. However, heavy fertilization and covering cultivation are used to produce off-season bamboo shoots, resulting in soil degradation and a decline in site productivity. This study investigated how compound fertilizer decrement and water-soluble humic acid fertilizer application affects soil properties and shoot yield in Lei bamboo plantations of subtropical China. The soil nutrients, enzyme activities, and shoot yield were examined, the bacterial community structure was determined using the high-throughput sequencing method, and their relationships were evaluated under different fertilization treatments: single compound fertilizer and compound fertilizer decrement with water-soluble humic acid fertilizer applications. Compared with those after single compound fertilizer treatments (CF1, CF2), water-soluble humic acid fertilizer addition (CF2HA1, CF2HA2) increased soil organic carbon (SOC), available phosphorus (AP), microbial biomass nitrogen (MBN) contents, the ratio of SOC to total nitrogen (C/N), and sucrase and acid phosphatase (Acp) activities, and decreased alkali hydrolyzed nitrogen (AN) and microbial biomass carbon (MBC) contents. The bacterial community phyla comprised 83.62%–86.16% Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, and Chloroflexi. Water-soluble humic acid fertilizer application also significantly increased yields by over 30%. AP and MBN were important drivers affecting soil bacterial communities, whereas SOC, MBN, and Chloroflexi affected Lei bamboo shoots. Overall, compound fertilizer decrement and water-soluble humic acid fertilizer application shifted the available soil nutrients, sucrase and Acp activity, bacterial community diversity, and shoot yield. An improved understanding of humic acid and the application of humic acid water-soluble fertilizer are of great significance for soil improvement, ecological restoration, and the sustainable management of bamboo forests in the future.