Penetration resistance as affected by shallow-cut land leveling and cropping

Land leveling is a form of soil disturbance that alters soil physical properties and is commonly conducted in fields cropped to rice (Oryza sativa L.) to facilitate more uniform distribution of irrigation water. Few studies have been conducted on the effects of shallow-cut land leveling on spatial variation of soil penetration resistance. The objective of this study was to characterize the effects of shallow-cut land leveling and cropping on penetration resistance in a soil cropped in a rice-soybean (Glycine max L.) rotation in the Mississippi River Delta region of eastern Arkansas, USA. The study area consisted of a 50 point grid occupying 0.36 ha of a larger field that was land leveled in April 2002. Penetration resistance (i.e., cone index, CI) was measured at 0.05 m intervals to 0.35 m with a penetrometer at each grid point before, immediately after, and roughly 1 year after land leveling. Land leveling increased (P<0.05) CI at all depths and the variability associated with CI below the 0.05 m depth and disrupted the spatial variability and distributions of CI throughout the study area. Land leveling resulted in a 0.1 m shallower hard pan, which effectively reduced the soil volume for subsequent crop root growth by 50%. The shallower pan is agronomically significant because, despite being necessary in a rice cropping system to hold irrigation water, proper management for optimum yield of alternative non-flood-irrigated crops grown in rotation with rice will be challenging due to the altered soil physical condition following land leveling. Deep-tillage may be required following shallow-cut land leveling to help alleviate the poor soil physical condition for upland crops grown in rotation with rice.