Liu Xiao, Guo Kangli, Huang Lin, Ji Zhengyu, Jiang Huimin, Li Hu, Zhang Jianfeng
Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agriculture Sciences, Beijing, China.
Sewage Purification Co., Ltd., Zhengzhou, China.
PLoS One. 2017 May 17;12(5):e0177796. doi: 10.1371/journal.pone.0177796. eCollection 2017.
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.
堆肥污泥（CS）被认为是土壤养分的丰富来源，对土壤的物理、化学和生物学特性有显著影响，但其对土壤中特定酶活性的影响却被忽视。本实验研究了2012 - 2015年中国北方玉米 - 小麦轮作系统下，潮土型干润淋溶土中参与碳、氮和磷循环的酶的绝对活性和比活性、土壤微生物功能多样性以及土壤群落组成。施用CS导致微生物量碳（MBC）增加，且其与总有机碳（TOC）和微生物量氮（MBN）的比值也增加。除磷酸酶外，CS处理土壤中的绝对酶活性增加，而所有酶的比活性均下降，尤其是在CS最高剂量（45 t ha-1）时。CS处理土壤中土壤微生物群落的多样性也增加，而由于比酶活性降低，在较高剂量的CS下其功能多样性下降。这些变化表明，施用CS导致非代谢活跃和资源利用效率更高的微生物（即真菌）占主导地位。冗余分析表明，土壤酶活性的根本变化取决于土壤pH值。通过Pearson相关系数判断，土壤性质的变化，尤其是土壤微生物活性和土壤微生物区系组成（以以下比率衡量：MBC/TOC、MBC/MBN和TOC/LOC，即易分解有机碳）对比酶活性的影响大于对绝对酶活性的影响。因此，比酶活性是监测添加CS对土壤微生物群落活性和结构影响的比绝对酶活性更准确的参数。
