Responses of absolute and specific enzyme activity to consecutive application of composted sewage sludge in a Fluventic Ustochrept

PLoS One. 2017 May 17;12(5):e0177796. doi: 10.1371/journal.pone.0177796. eCollection 2017.

Abstract

Composted sewage sludge (CS) is considered a rich source of soil nutrients and significantly affects the physical, chemical, and biological characteristics of soil, but its effect on specific enzyme activity in soil is disregarded. The present experiment examined the absolute and specific enzyme activity of the enzymes involved in carbon, nitrogen, and phosphorus cycles, the diversity of soil microbial functions, and soil community composition in a Fluventic Ustochrept under a maize-wheat rotation system in North China during 2012-2015. Application of CS led to increase in MBC and in its ratio to both total organic carbon (TOC) and microbial biomass nitrogen (MBN). Absolute enzyme activity, except that of phosphatase, increased in CS-treated soils, whereas specific activity of all the enzymes declined, especially at the highest dose of CS (45 t ha-1). The diversity of soil microbial community also increased in CS-treated soils, whereas its functional diversity declined at higher doses of CS owing to the lowered specific enzyme activity. These changes indicate that CS application induced the domination of microorganisms that are not metabolically active and those that use resources more efficiently, namely fungi. Redundancy analysis showed that fundamental alterations in soil enzyme activity depend on soil pH. Soil specific enzyme activity is affected more than absolute enzyme activity by changes in soil properties, especially soil microbial activity and composition of soil microflora (as judged by the following ratios: MBC/TOC, MBC/MBN, and TOC/LOC, that is labile organic carbon) through the Pearson Correlation Coefficient. Specific enzyme activity is thus a more accurate parameter than absolute enzyme activity for monitoring the effect of adding CS on the activities and structure of soil microbial community.

MeSH terms

  • Bacteria / classification
  • Bacteria / enzymology
  • Bacteria / isolation & purification
  • Bacterial Proteins / metabolism*
  • Carbon / analysis
  • Fungal Proteins / metabolism*
  • Fungi / classification
  • Fungi / enzymology
  • Fungi / isolation & purification
  • Nitrogen / analysis
  • Phosphorus / analysis
  • Sewage / chemistry*
  • Sewage / microbiology
  • Soil / chemistry*
  • Soil Microbiology
  • Soil Pollutants / analysis

Substances

  • Bacterial Proteins
  • Fungal Proteins
  • Sewage
  • Soil
  • Soil Pollutants
  • Phosphorus
  • Carbon
  • Nitrogen

Grants and funding

The research was financially supported by joint laboratory with Chinese Academy of Agriculture Sciences and University of New Hampshire. This research was also funded by National Natural Science Foundation of China, 21577172, 41501322 (http://program.most.gov.cn/), the International Scientific and Technological Cooperation Projects of China 2015DFA20790 (http://www.istcp.org.cn/), the National Basic Research Program (973 program) of China, 2013CB127406 (http://program.most.gov.cn/), the project of central public welfare scientific research institute, 161032016043 (http://program.most.gov.cn/) and National Key Research and Development Program, 2016YFE0101100 (http://program.most.gov.cn/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The commercial affiliation (Sewage Purification Co., Ltd) provided support in the form of salaries for author (HL), but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.