Cotton Conservation System and Irrigation Effects On Soil Carbon Pools of Tennessee Valley (Alabama) Paleudults.

Soil organic carbon (SOC) pools directly influence soil quality and are affected by agronomic management.  Labile carbon (C) fractions are frequently identified as active C, which is a potential soil quality indicator and related to C sequestration. Soils of the Tennessee Valley region in Alabama are intensively utilized for cotton (Gossypium hirsutum L.) production.  This inherently fragile soil resource has been historically degraded due to intensive monoculture cultivation, but research has shown productivity can be enhanced by using irrigation and conservation systems that improve dynamic soil quality.  The objective of this study is to determine active C dynamics in cotton produced in a conservation system [no-tillage with and without a winter rye (secale cereale) cover crop] using subsurface drip irrigation (SDI).  The experimental site is a field-scale test located in the Tennessee Valley Region at Belle Mina, AL, with Decatur (fine, kaolinitic, thermic Rhodic Paleudults) soils possessing silt loam textured surface horizons. Soil organic carbon and potassium permanganate oxidizable C (active C) data will be presented for soil samples (0-10 cm and 10-20 cm depths) collected from both SDI and non-irrigated plots, with and without cover.  From 2006-2008, SOC at both depths was affected more by cover than SDI, with a significant interaction between these effects.  Preliminary analyses for active C suggest significantly greater active C in the cover crop treatment compared with the no cover treatment.  Subsurface drip irrigation is a relatively new management tool available to growers of this region, so studies evaluating its interactive effects with cropping systems on soil properties indicative of soil quality are critical for its thorough evaluation.