The Evaluation of Soil Carbon Levels on Post-contract Conservation Reserve Program Lands in Southwestern North Dakota using Multiple Agricultural Use Practices

Abstract

The Conservation Reserve Program (CRP) removes highly erodible lands from production for a contract period of 10 to 15 years. During the contract period permanent vegetation cover is established, allowing biological, chemical, and physical soil properties to stabilize and potentially improve. As CRP contracts expire, these idle lands may return to agricultural use. Understanding the influence of various agricultural practices on post-contract CRP lands will enable landowners to make the best management choices. This four-year study focused on the potential impacts of livestock grazing, cropping systems, and vegetative cover on soil carbon levels and species composition on post-contract CRP lands in a semi-arid climate. A randomized complete block design (n = 2) was developed using four treatments, including season-long grazing (SL), a one-cut haying system (HAY), barley: com rotational cropping system (CROP), and non-use simulating idle CRP (CTRL). Moderate grazing targeting 50% herbage disappearance occurred on the SL treatment from mid-June through early January. Barley was harvested as hay in mid-July. Com was left as standing stockpiled forage. Cattle grazed the barley stubble and standing com from early January through mid-April. Four 100-meter transects were established in each treatment and were used to collect vegetation and soil data. Soil samples were analyzed for inorganic, organic, and total carbon. Results indicate that grazing, haying, and cropping systems do not adversely affect soil carbon levels after 4 years of agricultural use when compared to idle CRP. Species composition on grasslands also did not change during the study due to grazing, haying, or non-use. The findings of this study support the use of no-till cropping, one-cut haying, and moderate grazing for maintaining soil carbon levels and species composition on post-contract CRP lands.