Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/1999
Publication Date: N/A
Interpretive Summary: Some Conservation Reserve Program (CRP) contracts were not renewed after the original period. In some cases, producers chose to return the land to crop production, and information was needed regarding which practices were suitable for returning the CRP grassland to cropland. A study on Pullman soil near Bushland, Texas, involved no-, reduced, sweep, disk, moldboard plus disk, burn-sweep, and burn-disk tillage where grass was retained and the same, except burn-sweep and burn-disk, where grass was mowed and baled before applying treatments. Fertilizer (ammonium nitrate) was applied at 0, 30, and 60 lb N/ac. in 1995, and at 0, 60, and 120 lb N/ac. in 1996 and 1997. The soil was dry when treatments were applied and never was filled with water at planting time. Grain sorghum yield was less than or equal to 640 lb/ac. in 1995 and the 1995-1996 winter wheat crop failed due to low soil water contents and low rainfall. Sorghum was not planted in 1996 because of a drought. Sorghum yielded from 2020 to 4200 lb/ac. in 1997. Wheat yielded from 1260 to 1770 lb/ac. in 1996-1997. Retaining or removing grass had little effect on yields. Applying fertilizer affected sorghum yields only slightly, but increased wheat yields. Grass control was poor with no-tillage. Disk tillage to plow out the grass and loosen the soil appears best for initially converting the CRP grassland to cropland in this semiarid region. For later crops, reduced- or no-tillage could be adopted to control erosion. Because of low soil water contents when treatments were applied, a 90-day period was too short for storing enough soil water for good crop yields. Not planting a crop soon after plowing out the grass when precipitation is low would provide more time for storing soil water and provide a better chance for getting good crop yields.
Technical 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 no-, reduced, sweep, disk, moldboard plus disk, burn-sweep, and burn-disk tillage with grass retained and the same, except burn-sweep and burn-disk, with grass removed before imposing the treatments. Fertilizer (ammonium nitrate) 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 less than or equal to 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. Grass retention or removal affected yields slightly. Fertilization affected sorghum yields slightly and increased wheat yields. Grass 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-day period is inadequate for obtaining adequate soil water storage unless precipitation is much above normal. Foregoing planting a crop soon after grass termination when precipitation is low would provide more time for storing soil water and increase the potential for obtaining favorable yields.