Effects of Furrow Dikes on Water Conservation and Dryland Crop Yields

Eliminating or reducing storm runoff in the Southern Great Plains can increase soil-water storage, decrease erosion, and increase crop yields. The primary objectives of this study were (i) to examine the potential of furrow dikes as a conservation practice to retain runoff and increase crop yields, and (ii) to examine the effects of furrow diking on sorghum [Sorghum bicolor (L.) Moench] and sunflower (Helianthus annuus L.) production. Analyses of 28 yr of runoff records show furrow diking has the potential to retain 25 to 30 mm of runoff annually. The maximum annual runoff retention by diking observed during the 14 crop years of research (three separate experiments conducted between 1980 and 1985) was 111 mm. The maximum increase in sorghum yield measured as a result of diking was 2.46 Mg/ha. Conditions responsible for maximum yield responses of sorghum to diking were: (i) annual cropping, (ii) large rainfall/runoff events occurring prior to or early in the growing season, and (iii) limited growing season precipitation. Diking increased annual cropped sorghum yields on graded and contour furrow treatments by 49 and 14%, respectively, whereas water use efficiencies were increased by 25 and 16%. Yields and water use efficiencies from diked treatments on graded and contour furrows were as great as yields and water use efficiencies from a leveled minibench treatment, indicating that from a crop production standpoint, furrow diking was as effective as land leveling in retaining runoff and increasing crop yields. Sunflower yields were increased significantly by diking during 1 yr out of 3 when sunflower was grown after 76 weeks of fallow, whereas sorghum yields were not affected by diking after fallow. Decreasing row spacing from 1.0 to 0.75 m resulted in a significant increase in the 3-yr avg yield of sorghum and sunflower of 1.0 and 0.14 Mg/ha, respectively, when grown after fallow, indicating that considerable opportunity for improving summer crop production may exist simply by changing to a narrow row spacing. A regression equation relating runoff from graded furrows to runoff from contour flat-tilled graded terraces showed increased runoff from graded furrows, particularly from small storms.