Conversion of Conservation Reserve Program (CRP) Grassland for Dryland Crops in a Semiarid Region

Abstract

Information was needed regarding practices suitable for returning grassland to cropland when Conservation Reserve Program (CRP) contracts expired. A study on Pullman soil (Torrertic Paleustoll) involved seven tillage treatments (no‐tillage and reduced, sweep, disk, moldboard plus disk, burn–sweep, and burn–disk tillage) with vegetation retained and the five non‐burn tillage treatments with vegetation removed before treatment. Fertilizer (NH4NO3) was applied at 0, 34, and 67 kg N ha−1 in 1995 and at 0, 67, and 134 kg N ha−1 in 1996 and 1997. Initial soil water contents were low, and soil never was filled with water at planting time. Sorghum [Sorghum bicolor (L.) Moench] yielded ≤720 kg ha−1 in 1995, and the 1995–1996 wheat (Triticum aestivum L.) crop failed. Sorghum was not planted in 1996 because of a drought. Sorghum yielded 2260 to 4700 kg ha−1 in 1997. Wheat yielded 1410 to 1980 kg ha−1 in 1996–1997. Vegetation retention or removal affected yields slightly. Fertilization affected sorghum yields slightly and increased wheat yields. Vegetation control was difficult with no‐tillage. Disk tillage to dislodge grass, followed by reduced‐ or no‐tillage, appears best for converting CRP grassland to cropland in this semiarid region. Because of low initial soil water contents, a 90‐d period is inadequate for obtaining adequate soil water storage unless precipitation is much above normal. Forgoing planting a crop soon after killing the vegetation when precipitation is low would provide more time for storing soil water and increase the potential for obtaining favorable yields.