Soil Properties' Response to Wheat Stubble and Corn Stubble Residue Management in Louisiana.

Crop residue plays an important role in improving soil fertility. Crop residue affects soil biological and chemical properties by increasing soil organic matter (SOM), nutrient cycling and availability, and microbial activity. Residue management significantly impacts the degree of the influences of crop residue on soil fertility. A total of 342 soil samples (0-2.5cm) were collected across tillage, no-till, and prescribed fire treatments of wheat stubble and corn stubble residue located on the Macon Ridge Research Station in Winnsboro, LA. Soil samples were collected in 2014 in wheat (Triticum spp.) stubble and corn (Zea mays) stubble residue under all three managements. A second soil sample collection under wheat stubble residue was taken in 2015 under prescribed fire and no-till. Samples were collected pre-management and at 1, 24, 168, 720, and 4320 hr intervals post-management and analyzed for soil chemical and biological properties. Additional samples were collected in corn stubble residue 6 hrs post-management, and in 2015, samples were also taken in wheat stubble residue 6 hrs and 168 hrs post-management. In wheat stubble, prescribed fire increased SOM and inorganic N relative to no-till and tilled. Prescribed fire increased β-glucosidase activity relative to tillage but was similar to β-glucosidase activity observed in no-till in wheat stubble. Prescribed fire did not increase N-acetyl-β-D-glucosaminidase activity in wheat stubble. Shifts in microbial communities were observed in wheat stubble residue with total bacteria, specifically Gram negative, and actinomycetes dominating the prescribed fire soil while relative abundance of arbuscular mycorrhizal fungi, saprophytic fungi, and fungi:bacteria dominated no-till and tillage soil. In corn stubble, prescribed fire increased SOM over time but did not increase inorganic N, β-glucosidase activity, or N-acetyl-β-D-glucosaminidase activity relative to no-till and tilled. In corn stubble, there was no distinct microbial community composition in response to residue management.