Short-term compost application increases rhizosphere soil carbon mineralization and stimulates root growth in long-term continuously cropped cucumber

Abstract

Continuous cropping, a common agricultural practice in the world, often results in soil degradation and eventually lead to crop yield decline over time. Composts application has several advantages such as improving soil quality and increasing crop yields. However, little information is available regarding the effect of compost application on crop growth in continuous cropping systems. In this study, we investigated three long-term (>15 years) continuously cropped cucumber soils to examine the effect of compost application on carbon mineralization of rhizosphere soils and plant growth. All three soils were treated with/without compost, Bacillus subtilis and their combination. In general, the amounts of cumulative carbon mineralization in soils treated with compost were larger than those in untreated soils. The initial carbon mineralization rate, m0, was significant higher in soils treated with compost than in untreated soils. Soil microbial biomass carbon (MBC) and root growth was significantly (P<0.05) increased by the compost addition, but was not statistically (P>0.05) affected by the bacterial inoculation in all soils. In compost-treated soils, there was a higher faction of thin roots (<0.5mm diameter) and a smaller fraction of thicker roots (>0.5mm diameter) compared with untreated soils. Cucumber fruit yield was significantly positively correlated with the CCM and MBC values. Our results suggested that short-term compost application increases rhizosphere soil carbon mineralization and stimulates root growth in long-term continuously cropped cucumber.