Variability of soil physical quality in uneroded, eroded, and depositional cropland sites

Erosion and deposition processes affect the physical quality of the soil. Thus, the objective of this study was to assess the effects of these processes on a long-term no-till corn agroecosystem in a humid-temperate region of the Midwest U.S. The study was conducted under on-farm conditions, in a field which experiences erosional and depositional processes. At the end of the dormant season, soil characteristics were tested for two depths (0-5 and 5-10cm) in uneroded (UN), eroded (ER), and depositional (DP) sites. The data showed that UN and ER were characterized by the highest and lowest soil shear strength (137.3 and 78.1KPa, respectively) and organic carbon concentration (35.6 and 30.3g kg-1, respectively). The highest and lowest aggregate stability (85.4% and 73.6%, respectively) and mean weight diameter (2.9 and 1.6mm, respectively) were observed in UN and DP. The highest and lowest penetration resistance (4.82 and 4.57MPa, respectively) and bulk density (1.49 and 1.33Mg m-3, respectively) were measured in ER and DP. An opposite trend was observed for the C:N ratio (8.2 and 9.6, respectively), and the value's color variable (4.6 and 4.9, respectively). No significant differences among the erosional phases were measured in the soil's total nitrogen concentration, hue and chroma color variables, texture, hydraulic conductivity, and intrinsic permeability. The erodibility factor was the lowest and highest in DP and ER (0.00326 and 0.00397Mg ha h ha-1 MJ-1 mm-1, respectively), and the effect of erosional phase on this factor was close to significant. In general, the effect of erosion and deposition on soil characteristics decreased with an increase in soil depth. This study suggests that the occurrence of positive feedbacks in ER and DP have led to accelerated erosional and depositional processes and the continuous degradation of the soil quality. A range of management practices should be considered in order to mitigate these processes and reduce negative impact on crop yields in such agroecosystems. © 2010 Elsevier B.V.