Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/19/2000
Publication Date: N/A
Interpretive Summary: Long-term experiments are needed to generate reliable information on how different management cropping systems may impact soil quality. However, only a few experiments have been conducted under the warm climatic conditions and sandy soils of the southeastern USA. This research was undertaken to determine the effect of four tillage systems on soil quality chemical indicators on two Coastal Plain soils in southwestern Alabama after 17 years. Four tillage systems (no-tillage, disk, chisel plow, and moldboard plow) were applied prior to planting the winter crop each year; varied summer crops were double cropped behind the winter crop using no-tillage during the period. We then determined soil pH, organic matter, and soil nutrients in the systems. Soil organic matter accumulation was inversely related to the level of soil disturbance (no- tillage> disk> chisel plow> moldboard plow). No tillage had twice the carbon compared to the moldboard plow treatment in the top 3 inches of soil. Surface applications of lime maintained an adequate soil pH even without tillage to incorporate the lime. Soil phosphorus did not accumulate in the surface soil, which suggests that phosphorus runoff and potential for contamination of surface waters may not be a problem in long-term conservation tillage systems on Coastal Plain soils. Soil organic matter proved to be a reliable indicator of other soil chemical properties. Adoption of conservation tillage with double cropping promotes sustainability for these soils in the Southeast.
Technical Abstract: The impact of tillage intensity on chemical soil quality indicators has not been evaluated in the long-term for soils of the Southeastern Coastal Plain. The long-term influence of four tillage systems [no- tillage (NT), disk, moldboard plow (MP), and chisel plow (CP)] on chemical soil quality indicators after 17 years was evaluated on a Benndale fine sandy loam and a Lucedale very fine sandy loam in the Coastal Plain region of Alabama. Soil pH, effective cation exchange capacity (CEC), soil organic carbon (SOC), and soil N, P, Zn, and Mn were determined on soil samples collected at depths of 0-1, 1-3, 3-6, 6- 9, and 9-12 inches. An accumulation of SOC occurred primarily in the top one inch with values of 2.76, 1.31, 1.27, and 1.04% C with NT, disk, CP, and MP, respectively, for the Benndale soil and 1.67, 1.00, 0.98, and 0.69% C, respectively, for the Lucedale soil. A slight decrease in pH (0.3 units) was observed at 6-12 inches with NT compared to other tillage treatments on the Lucedale soil. Extractable P was higher with NT than MP at the 9-inch depth on the Lucedale soil. On the Bendale soil, NT resulted in the greatest extractable P at the 6 to 9 inch depth. Regression showed that SOC and pH combined predicted 73% and 86% of the variation in CEC for the Benndale and Lucedale soils, respectively; SOC and pH were also tightly correlated to nutrient availability. Surface applications of lime maintained soil pH at an acceptable level within the plow layer of both soils and all tillage systems. As determined from chemical indicators of soil quality, adoption of conservation tillage with double cropping promotes sustainability for these soils.