Rural mixed pond water irrigation affected microbial community and eco-enzymatic stoichiometry of soil profiles

Abstract

The application of rural mixed pond water (RMW) for irrigation has become a relatively normal agricultural practice in China. However, it is not clear whether soil microbial activity and soil stored nutrients are influenced by RMW. In this study, soil samples were collected from a depth of 0–60 cm for determining their basic physicochemical properties, microbial biomass and soil enzyme activities, moreover, the eco-enzymatic stoichiometry ratio was determined to evaluate microbial nutrient requirements. Our results showed that, with the increase in the soil depth, dissolved organic carbon, available phosphorus, microbial contents, and extracellular enzyme activities declined. We observed an increment in the microbial biomass nitrogen (MBN; 1.44 fold) and microbial biomass carbon (MBC; 1.23 fold) from 0 to 10 cm after RMW irrigation. The latter was more stable below 40 cm of the soil layer independent of irrigation water. The increase in carrier length and angular carrier indicated that the microorganisms were limited by carbon (C) and phosphorus (P). The RMW irrigation significantly decreased the β-1,4-Nacetylglucosaminidase (NAG), the leucine aminopeptidase (LAP), and the phosphatase (AP). In addition, RMW irrigation increased the α-diversity of surface soil microorganisms but suppressed them in deeper soil profiles. The RDA analysis suggested that random NAG of exoenzymes had the greatest relative contribution to microbial diversity, with bacteria and fungi accounting for 27.1 % and 25.1 %, respectively. This study showed that RMW irrigation led to changes the soil extracellular enzyme activities, resulting in alterations the enzyme stoichiometry ratios and microbial nutrient acquisition strategies.