Identifying the best tillage system to maintain soil properties and crop yields after Conservation Reserve Program grassland conversion

The Conservation Reserve Program (CRP) is a United.States of Americae government program that provides financial incentives to transition marginal croplands to permanent grass cover to conserve soil and water. Few studies have evaluated the best tillage system that maintains soil properties when converting CRP back to cropland. Our objective was to determine how converting CRP to cropland under different tillage practices after three years affects soil C (carbon) stocks, physical and chemical properties, and winter wheat (Triticum aestivium L.) and corn (Zea mays L.) grain yields after 4 yr. We also reviewed literature on the topic to compare previous results against our findings. This experiment was conducted in Sidney, NE, USA on CRP that was converted to production farmland through four tillage practices no-till (NT), disk-sweep (DS), plow-sweep (PS) and deep plow-sweep (DPS) in 2017 and planted to a wheat-corn-fallow rotation. Organic C stock was reduced by 6% in PS and 15% in DPS compared to CRP in the 0–10 cm depth but not in the 0–60 cm. Tillage practice did not affect grain yields in our study but had inconsistent effects according to previous literature. In the upper 10 cm, wet aggregate stability was reduced by 41% in DS, 51% in PS, and 58% in DPS, dry aggregate stability was reduced by 66% in NT, 71% in DS, 74% in PS and 77% in DPS, and plant available water was reduced by 45% in NT, 50% in DS, 39% in PS and 43% in DPS treatment relative to CRP. However, treatments had no effect on cumulative infiltration rate and bulk density. The use of DS or NT when converting CRP to cropland caused the least negative impacts on soil properties when CRP was converted to cropland in our study and in previous studies reported in the literature. Minimizing soil disturbance by reduced or no tillage maintained relevant soil properties 3 yr after CRP conversion to cropland.