Short-term fallow practices drive soil bacterial community changes: A case study from China

Abstract

Fallowing is considered an effective self-recovery practice for farmland and is commonly applied in the management of cultivated land. Improved fallow practices may result in shorter fallow periods, but few studies have compared the benefits of different improved fallow practices as they relate to soil microbial ecology. We established 6 fallow treatments on a continuous sorghum cropping field. Three different kinds of vegetation were planted as the fallow vegetation, and 2 levels of fertilization were applied to each vegetation type. The fallow experiments were conducted over 3 years, and each plot was sampled 3 times. The bacterial community structure in the topsoil (0–20 cm) and subsoil (20–40 cm) was determined by DNA sequencing.The results showed that manure application could significantly change the bacterial community structure and assembly processes. Manure increased the abundance of plant growth-promoting rhizobacteria and bacterial communities associated with nutrient cycling. The unfertilized plots promoted bacterial communities associated with nitrogen fixation and plant residue decomposition. In terms of the effects of the different vegetation types, plant growth-promoting rhizobacteria benefited from spontaneous vegetation with manure during the fallow process, and they also benefited from maize-alfalfa vegetation with manure in the first and third years of this study. The unfertilized alfalfa-dahurian plots had positive effects on plant growth-promoting rhizobacteria starting in the second year, while fertilized fields did not exhibit increased rhizobacteria until the third year. If the fallow vegetation is maize-alfalfa and spontaneous vegetation, manure application is necessary. Therefore, farmland fallowing could be combined with animal husbandry. However, the interactions between vegetation and manure must be considered seriously.