Effects of exogenous organic acids and biological substrates on the structural characteristics of soil bacterial communities in coastal mudflat soils of salt-tolerant forage growth field

Abstract

Abstract Aims The high salinity of soil, nutrient scarcity, and poor aggregate structure limit the exploitation and utilization of coastal mudflat resources and the sustainable development of saline soil agriculture. In this paper, the effects of applying exogenous organic acids combined with biological substrate on the composition and diversity of soil bacterial community were studied in moderately saline mudflats in Jiangsu Province. Methods A combination of three exogenous organic acids (humic acid, fulvic acid, and citric acid) and four biological substrates (cottonseed hull, cow manure, grass charcoal, and pine needle) was set up. A total of 120 kg ha− 1 of organic acids and 5000 kg ha− 1 of substrates were used, plus two treatments, CK without application of organic acids and substrates and CK0 in bare ground, for a total of 14 treatments. Results No significant difference was found in the alpha diversity of soil bacterial community among all treatments (P > 0.05), with the fulvic acid composite pine needle (FPN) treatment showing the largest increase in each index. The beta diversity differed significantly (P ≤ 0.05) among all treatments, and the difference between citric acid–grass charcoal (CGC) and CK treatments was greater than that of other treatments. All treatments were effective in increasing the number of bacterial ASVs and affecting the structural composition of the community. Citric acid–cow manure, FPN, and CGC treatments were found to be beneficial for the relative abundance of Proteobacteria, Chloroflexi, and Actinobacteria, respectively. By contrast, all treatments triggered a decrease in the relative abundance of Acidobacteria. The changes in soil bacterial communities were closely related to the changes in soil salt alkali and nutrient characteristics induced by the addition of exogenous organic acids and biological substrates. Conclusions Adding exogenous organic acids and biological substrates provides a relatively independent microenvironment and sufficient nutrients for the life activities of different energy-type bacteria. It regulates the species composition and functional characteristics of bacterial communities by changing the structural characteristics of these communities in mudflats.