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

Abstract

Crop residue plays an important role in improving soil fertility. Crop residue affects soil biological and chemical properties by increasing soil organic matter, nutrient status and availability, and microbial activity. The degree of the effects of crop residue on soil fertility depends on the crop residue management practice. Samples were collected in 2014 in wheat (Triticum spp.) stubble and corn (Zea mays) stubble residue. A second soil sample collection under wheat stubble residue was taken in 2015 in the prescribed fire and no-till sections. A total of 342 soil samples (0-2.5cm) were collected across conventional tillage, no-till, and prescribed fire treatments of wheat stubble and corn stubble residue located on the Macon Ridge Research Station in Winnsboro, LA. Samples were collected pre-management (0 hr) and at 1, 24, 168, 720, and 4320 hr intervals post-management and analyzed for soil chemical (macronutrients and soil organic matter) and biological (microbial community structure and enzyme activities) properties. In 2015, additional samples were taken in wheat stubble residue 6 hrs and 168 hrs (1 week) post-management. Additional samples were collected in corn stubble residue 6 hrs post-management. Prescribed fire increased NO3--N relative to no-till and conventional tillage in wheat stubble. Prescribed fire increased β-glucosidase activity relative to conventional tillage but was similar to β-glucosidase activity observed in no-till. Short term changes in organic matter, nutrients, and enzyme activity were observed in prescribed fire, no-till, and conventional tillage. Shifts in microbial communities were observed in wheat stubble residue with Gram negative, total bacteria, and actinomycetes dominating the prescribed fire soil and abundance of arbuscular mycorrhizal fungi, saprophytic fungi, and fungi:bacteria dominated no-till and conventional tillage soil. The effects of management practices on microbial community structure was unable to be determined in corn stubble residue based on the fatty acid profiles tested in this study. While prescribed fire increased NO3--N and β-glucosidase activity, similarities between management were observed in NH4+-N, soil organic matter, and N-acetyl-β-D-glucosaminidase activity. Therefore, further research needs to be done in order to determine the most efficient crop residue management practice to optimize soil fertility.