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Soil Carbon, Nitrogen, and Aggregation in Response to Type and Frequency of Tillage

USDA-ARS, J. Phil Campbell Sr. Natural Resources Conservation Center, 1420 Experiment Station Rd., Watkinsville, GA 30677-2373

*Corresponding author (afranz{at}arches.uga.edu).

ABSTRACT

Little information exists on the biogeochemical effects of combining no-tillage planting with paraplowing (to improve deep water penetration) or with secondary tillage (to control weeds). We determined surface residue and soil C and N pools (total, particulate, microbial biomass, and mineralizable) and water-stable aggregation at depths of 0 to 25, 25 to 75, and 75 to 150 mm from a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludults) in Georgia. Soil tillage treatments were a factorial arrangement of tillage type [(i) minimal disturbance with in-row chisel at planting, (ii) no-tillage planting with autumn paraplow, and (iii) no-tillage planting with secondary tillage during the summer] and tillage frequency [(i) every year, (ii) every second year, and (iii) every fourth year]. No-tillage planting without further disturbance occurred in remaining years. At a depth of 0 to 25 mm, basal soil respiration averaged 9 mg kg^-1 d^-1 with conventional tillage, 27 mg kg^-1 d^-1 with no-tillage planting and soil disturbance every year, and 36 mg kg^-1 d^-1 with no-tillage planting and soil disturbance every fourth year. At a depth of 0 to 150 mm, mean-weight diameter averaged 1.03 mm with conventional tillage, 1.12 mm with paraplow, 1.17 mm with secondary tillage, and 1.23 mm with in-row chisel. No-tillage planting with alternative tillage types and frequencies not only improved surface soil properties compared with conventional tillage, but also improved seed cotton yield an average of 19%. Biophysical improvement of surface soil structure would presumably lead to greater water infiltration and improved water use efficiency in the long term.

Received for publication March 23, 1998.