Soil Properties and Fallow Season Vegetation Response to Prescribed Fire in Crop Residue.

Residue management programs vary based on the residue, with prescribed fire serving as a critical practice in Mid-South agriculture. A total of 128 soil samples (0-2.5cm) were collected across tilled, no-till, and burned treatments of wheat (Triticum spp.) stubble located on the Macon Ridge Research Station in Winnsboro, La. Samples were collected pre-burn and at intervals of 1, 24, 168, and 720-hrs post-burn and analyzed for soil chemical (macronutrients, and soil organic matter (SOM)) and biological (microbial community structure and enzyme activities) properties. Short-term (up to 168-hrs) changes in SOM were not measured; however, SOM decreased (2.62 to 2.41 g kg-1) at 720-hrs post-burn. No difference in SOM was measured between burned and no-till treatments; however, tillage decreased (8%) SOM. Nitrate-N increased 1-hr and again 168-hrs post-burn, decreasing to pre-burn levels at 24 and 720-hrs post-burn. A similar increase at 1-hr post-burn was observed in no-till samples; however, no difference in NO3--N was measured in tilled samples. Despite no treatment differences in NH4+-N concentrations, the highest concentrations were observed 24-hrs post-burn (25 mg kg-1) before decreasing to pre-burn concentrations 720-hrs post burn. This decrease in NH4+-N coupled with the observed increase in NO3--N in burned soils may be the result of increased nitrification rates. β-glucosidase activity was lowest 1-hr post-burn but had increased to its maximum 168-hrs post-burn. The decrease in β-glucosidase activity was also observed in no-till samples collected at the same intervals; however, recovery rate was slower than that observed in burned samples. In general, β-glucosidase activity was lowest in tilled samples. While prescribed fire influenced soil chemical and biological properties, observed differences in no-till samples suggests additional factors need to be identified. Overall, the prescribed fire effects on these soil properties can cause shifts in soil microbial communities that may have far reaching implications.