LEGUME, GRASS, AND CONSERVATION RESERVE PROGRAM EFFECTS ON SOIL ORGANIC MATTER RECOVERY

Active pools of soil organic matter (SOM) can recover to native levels on formerly cultivated fields that are abandoned for ≈50 yr, but the short-term (<10 yr) recovery dynamics of SOM and nutrient supply have not been widely investigated. In several fields on a farm in southeastern Wyoming that had been involved in the Conservation Reserve Program (CRP, a federal program that pays landowners to convert cultivated land into revegetated grasslands), we compared C and N in several SOM pools (coarse particulate organic matter [POM, between 500 μm and 2 mm], fine POM [53–500 μm], and total SOM), and we compared potential C and N mineralization in active pools responsible for nutrient supply. The two CRP treatments, planted 6 yr prior to this study, were an ≈80% legume:20% grass mixture (HL CRP) and a 20% legume:80% grass mixture (LL CRP). To quantify SOM accumulations directly due to increased plant inputs within CRP fields, we also compared SOM pools under legumes and grasses relative to plant interspaces, w...