Responses of microbial activity, abundance, and community in wheat soil after three years of heavy fertilization with manure-based compost and inorganic nitrogen

A three-year field experiment in a winter wheat-rice cropping system was performed to compare the influence on soil microbial parameters including microbial activity, abundance and community by heavy application of manure-based compost (CP) and inorganic nitrogen (CF, inorganic nitrogen applied as urea). The same amount of total nitrogen that was calculated from the local farming habits was applied in each season for the two treatments. Samples were analyzed after the third season of wheat harvested. In contrast to the untreated control (CK), CP and CF treatments both significantly increased the soil nutrient content (p < 0.05) with converse results obtained for improvements in soil water-holding capacity and acidification. Heavy application of organic compost markedly increased the soil microbial activity and gene copies of bacteria, archaea, and ammonia-oxidizing bacteria (AOB). However, pyrosequencing results demonstrated that heavy application of inorganic nitrogen had no influence on soil bacterial diversity. Diversity was significantly decreased by organic compost. Changes occurred in the bacterial community composition in compost treated soils, and most abundant taxa correlated with the moisture content, pH, organic C, total N, available P, and available P. The findings of this study indicated that compost application was not always beneficial to soil quality, and might decrease soil diversity. Therefore, studies to maintain the relationship between compost application rate and microbial diversity should be further conducted to protect soil ecosystems against disturbances