Short-term effects of land leveling on soil chemical properties and their relationships with microbial biomass

Spatial variability and distributions of soil chemical properties and the relationships between soil chemical and biological properties are not well characterized in agroecosystems that have been land leveled to facilitate more uniform delivery of irrigation water. The objectives of this study were to characterize the short-term impacts of land leveling on the magnitudes, spatial variability, and spatial distributions of soil chemical properties and to evaluate the impact of land leveling on the relationships between soil chemical properties and microbial biomass in a Stuttgart silt loam (fine, smectitic, thermic Albaqultic Hapludalf) used for irrigated soybean [Glycine mar (L.) Merr.] and rice (Oryza sativa L.) production in the Mississippi Delta region of eastern Arkansas. A grid-sampling approach was used to characterize pre- and postleveling soil chemical properties and microbial biomass. Results of this study demonstrate that land leveling, a severe form of anthropogenic soil disturbance, causes significant alteration of the magnitudes, spatial variability, and spatial distributions of many soil chemical properties. Soil electrical conductivity (EC) and the contents of P, K, Mg, Na, S, Mn, and Cu in the top 10 cm significantly increased, while soil pH and organic matter (OM) and Fe contents significantly decreased, as a result of land leveling. Land leveling also significantly altered many linear relationships among soil chemical properties and microbial biomass. The benefit of improved water distribution must be weighed against the relatively severe and immediate alteration of soil properties and natural processes brought on by land leveling. Further research is required to ascertain long-term effects of altered soil biogeochemical properties on crop growth as a result of land leveling.