A high clay-content argillic horizon occurring 10 to 100 cm below the surface restricts soil water movement and nutrient efficiency of claypan soils, which affect soil quality related to production and environmental buffering. The objective of this study was to determine the impacts of long-term (12 yr) of annual cropping systems (ACS) and conservation reserve program (CRP) practices on the soil quality for a claypan soil in north central Missouri. In 2002, soil cores were collected (0- to 7.5-, 7.5- to 15-, and 15- to 30-cm depths) from summit, backslope, and footslope landscape positions (LP). Management systems included: (i) annual cropping system 1 (ACS1), mulch tillage corn-soybean rotation system; (ii) annual cropping system 2 (ACS2), a no-till corn-soybean rotation system; (iii) annual cropping system 3 (ACS3), a no-till corn-soybean-wheat rotation system with red clover as a cover crop; and (iv) CRP, a continuous cool-season grass and legume system. No interactions were observed between cropping system and LP. At the 0- to 7.5-cm soil depth, CRP increased SOC storage by 33% and total nitrogen (TN) storage by 34%. Soil aggregation under CRP management was more than double that of the ACS. On the backslope, soil aggregation was significantly higher than on the footslope. SOC and TN were significantly higher on the footslope than on the backslope at the 7.5- to 15-cm soil depth. These results show that claypan soil quality was not significantly altered by ACS management but was greatly enhanced under CRP management.
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