Conservation System Impacts on Soil Properties and Water-Use Efficiency in the Southeastern U.S. Coastal Plain
Type of Degreethesis
Agronomy and Soils
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Conservation practices, such as cover cropping, crop rotation, and conservation tillage, have become an integral part in improving and sustaining cropping systems in the Coastal Plain region of the southeastern U.S., where soil quality is degrading and crop productivity is declining due to intensive tillage and row crop production on highly erodible soils. Planting winter cover crops instead of leaving row crop fields fallow can decrease erosion, increase water infiltration, and improve soil quality by adding organic matter. This study was conducted in the southeastern U.S. Coastal Plain region on a Dothan fine sandy loam to analyze soil properties and crop water-use efficiency as affected by conservation systems. The first objective of this study was to evaluate the effects of long-term (>20 years) cover cropping with oat (Avena sativa L.), rye (Secale cereale L.), wheat (Triticum aestivum L.), and fallow treatments and short-term (<1 year) cover cropping with oat, crimson clover (Trifolium incarnatum L.), oat/rye mixture, and fallow treatments on soil macroporosity, bulk density, saturated hydraulic conductivity (Ksat), and carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) distributions. Soil under oat and rye had significantly higher Ksat values than soil under fallow. When data from the two trials were compared, Ksat in soils under oat was significantly higher in the short-term trial than in the long-term trial. Differences in Ksat between trials were likely due to differences in soil management of the two areas. The presence of oat, rye, and wheat cover crops increased total soil C and N in the top 0- to 5-cm depth over the fallow treatment in the long-term trial, which indicates that cover crops can improve C and N storage in Coastal Plain soils at the surface layer over time. Soil P and S were not affected by cover crop species or duration of cover cropping. Other farming practices in the Coastal Plain region have also impacted soil and crop properties. Farmers in the region have frequently used the traditional rotation (TR), which includes peanut (Arachis hypogaea L.) rotated with cotton (Gossypium hirsutum L.) and intensive tillage with a moldboard plow (MP). Since this system facilitates the degradation of soil quality through increased erosion and loss of organic matter, a sod-based rotation (SBR) with the use of conservation strip tillage (ST) was investigated. The SBR implemented two years of bahiagrass (Paspalum notatum Flueggé) into the peanut-cotton rotation, which decreased disease, improved soil quality, and increased peanut yields. The second objective of this study was to analyze the effects of crop rotation (SBR and TR) and tillage (ST and MP) on yield and water-use efficiency (WUE) of peanut and cotton in the Coastal Plain region. Cotton yield did not differ by rotation or tillage, while peanut yield was highest in the sod-based rotation under strip tillage and lowest in the traditional rotation under strip tillage and moldboard plow tillage. Rotation and tillage did not affect WUE in peanut or cotton, suggesting that WUE did not influence the increase in peanut yield in the sod-based rotation. However, it can be concluded that the sod-based rotation, especially managed with strip tillage, can significantly improve peanut yield compared to the traditional rotation.