Effects of reclaimed water irrigation and nitrogen fertilization on the chemical properties and microbial community of soil

The ecological effect of reclaimed water irrigation and fertilizer application on the soil environment is receiving more attention.Soil microbial activity and nitrogen（N）levels are important indicators of the effect of reclaimed water irrigation on environment.This study evaluated soil physicochemical properties and microbial community structure in soils irrigated with reclaimed water and receiving varied amounts of N fertilizer.The results indicated that the reclaimed water irrigation increased soil electrical conductivity（EC）and soil water content（SWC）.The N treatment has highly significant effect on the ACE,Chao,Shannon（H）and Coverage indices.Based on a 16S ribosomal RNA（16S rRNA）sequence analysis,the Proteobacteria,Gemmatimonadetes and Bacteroidetes were more abundant in soil irrigated with reclaimed water than in soil irrigated with clean water.Stronger clustering of microbial communities using either clean or reclaimed water for irrigation indicated that the type of irrigation water may have a greater influence on the structure of soil microbial community than N fertilizer treatment.Based on a canonical correspondence analysis（CCA）between the species of soil microbes and the chemical properties of the soil,which indicated that nitrate N（NO3-–-N）and total phosphorus（TP）had significant impact on abundance of Verrucomicrobia and Gemmatimonadetes,meanwhile the p H and organic matter（OM）had impact on abundance of Firmicutes and Actinobacteria significantly.It was beneficial to the improvement of soil bacterial activity and fertility under 120 mg kg^-1 N with reclaimed water irrigation.

Soil Microbiological Activity and Carbon Dynamics in the Current Climate Change Scenarios:A Review

Microbial activities are affected by a myriad of factors with end points involved in nutrient cycling and carbon sequestration issues.Because of their prominent role in the global carbon balance and their possible role in carbon sequestration, soil microbes are very important organisms in relation to global climate changes. This review focuses mainly on the responses of soil microbes to climate changes and subsequent effects on soil carbon dynamics. An overview table regarding extracellular enzyme activities(EAA) with all relevant literature data summarizes the effects of different ecosystems under various experimental treatments on EAA. Increasing temperature, altered soil moisture regimes, and elevated carbon dioxide significantly affect directly or indirectly soil microbial activities.High temperature regimes can increase the microbial activities which can provide positive feedback to climate change, whereas lower moisture condition in pedosystem can negate the increase, although the interactive effects still remain unanswered. Shifts in soil microbial community in response to climate change have been determined by gene probing, phospholipid fatty acid analysis(PLFA),terminal restriction length polymorphism(TRFLP), and denaturing gradient gel electrophoresis(DGGE), but in a recent investigations,omic technological interventions have enabled determination of the shift in soil microbe community at a taxa level, which can provide very important inputs for modeling C sequestration process. The intricacy and diversity of the soil microbial population and how it responds to climate change are big challenges, but new molecular and stable isotope probing tools are being developed for linking fluctuations in microbial diversity to ecosystem function.