Efficacy of Nitrogen-fixing Bacteria Combined with Different Nitrogen Fertilizers in Improving Enzymatic Activity and Nitrogen in Reclaimed Soil

Abstract

【Objective】 Reclaimed soils are usually poor in nutrients and the aim of this paper is to investigate the efficacy of nitrogen-fixing bacteria combined with different nitrogen fertilizations in improving fertility of reclaimed soils. 【Method】 The experiments were conducted in pots filled with soil collected from a subsidized coal mining. The soil was incubated with nitrogen-fixing bacteria combined with different nitrogen fertilizers. In each treatment, we measured carbon and nitrogen in microbial biomass, enzymatic activity, total nitrogen, and ammonium and nitrate nitrogen in the soil. 【Result】 Combining nitrogen-fixing bacteria with ammonium or nitrate nitrogen fertilizer increases carbon and nitrogen in microbial biomass, total dissolved nitrogen, ammonium nitrogen in the soil. Compared with treatment with nitrate and ammonium nitrogen fertilization only, their combination with nitrogen-fixing bacteria increases the activity of catalase, sucrase, protease and urease by 4.96%, 17.85%, 12.53% and 6.12% respectively. Correlation analysis shows a close relationship between soil nutrients, enzymatic activity and carbon and nitrogen in microbial biomass; the activity of sucrase, protease and urease is positively correlated with total nitrogen, total dissolved nitrogen and ammonium nitrogen in the soil (P<0.01); the enzymatic activity is positively correlated with nitrate nitrogen (P<0.05); a positive correlation exists between carbon and nitrogen in microbial biomass and total dissolved nitrogen in the soil (P<0.05). Principal component analysis shows that ammonium nitrogen fertilization combined with nitrogen-fixing bacteria gives the best soil quality. 【Conclusion】 Combining nitrate and ammonium nitrogen fertilization with nitrogen-fixing bacteria can significantly increase soil microbial biomass and nitrogen content, and it can be used as an improved agricultural practice to improve quality of reclaimed soil from coal mining.

Keywords

• nitrogen fertilizer forms
• nitrogen-fixing bacteria
• dissolved total nitrogen
• reclaimed soil
• soil enzyme activity