Tillage intensity effects on chemical indicators of soil quality in two coastal plain soils

Few experiments in the coastal plain region of the southeastern United States have reported the effect of long-term tillage and tillage intensity on chemical soil quality indicators. The purpose of this study was to determine the 17-year influence of four tillage systems on chemical soil quality indicators in a Benndale fine sandy loam (coarse-loamy, siliceous, semiactive, thermic, Typic Paleudults) and a Lucedale very fine sandy loam (fine-loamy, siliceous, subactive, thermic, Rhodic Paleudults) in the coastal plain region of Alabama. Tillage systems were no-tillage, disk, moldboard plow, and chisel plow under varied double-cropping in a randomized complete block design with four replications. Soil pH, sum of extractable bases, soil organic carbon (SOC), and soil nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K), zinc (Zn), manganese (Mn), copper (Cu), and iron (Fe) were determined on soil samples collected at depths of 0-2.5, 2.5-7.5, 7.5-15.0, 15.0-22.5, and 22.5-30 cm. Soil carbon (C) accumulation occurred primarily in the top 2.5 cm, varied by soil type, and was inversely proportional to tillage intensity. The coarse textured Benndale soil averaged 27.6, 13.1, 12.7, and 10.4 g C kg(-1) soil with no-tillage, disk, chisel, and moldboard plow management, respectively, in the top 2.5 cm. The finer textured Lucedale soil averaged 16.7, 10.0, 9.8, and 6.9 g C kg(-1) soil, for the same treatments and depth, respectively. Surface applications of lime maintained soil pH at an acceptable level within the plow layer on both soil types and all tillage systems. Extractable P was higher with no-tillage than moldboard plowing to the 22.5 cm depth on the Lucedale soil. On the Benndale soil, P tended to accumulate at the 15 to 22.5 cm depth with tillage systems other than moldboard plowing, and no-tillage had the most extractable P at these depths. Soil C and pH combined proved effective as continuous pedotransfer functions, predicting 73% and 86% of the variation in sum of extractable bases for the Benndale and Lucedale soils, respectively. As determined from chemical indicators of soil quality, adoption of conservation tillage with doublecropping is a sustainable practice for these soils.