Doctor of Philosophy (PhD)
Plant, Environmental Management and Soil Sciences
Surface water quality impairment is often associated with agricultural activities. In this study, the effects of three sugarcane residue management techniques, namely burning (BR), shredding (SR), and retention (RR) of residues on: surface water quality, carbon export, and chemical composition of organic matter in the runoff sediments were characterized. Separate studies were conducted to evaluate predictive relationships for biochemical oxygen demand (BOD) in agricultural effluents, and the effectiveness of bauxite residues (red and brown muds) in reducing soluble nutrient/pollutant release from manure-impacted soils. All the selected water quality parameters were determined using EPA-approved analytical methods. The RR technique exported lower total suspended solids (TSS), total phosphorus (TP), BOD5, and inorganic anion loads compared to the BR and SR techniques during the study period. Rainfall amount correlated with TSS, BOD5, total Kjeldahl nitrogen (TKN), TP, nitrate-N, and nitrite-N exports in each treatment, and runoff turbidity significantly correlated with TSS (R2 = 0.95, P < 0.001).The BR treatment exhibited higher total carbon (TC), total organic carbon (TOC), and particulate organic carbon (POC) export, and these parameters were also positively correlated to runoff turbidity and TSS (R2 = 0.42-0.87, P < 0.001). The pyrolysis-GC/MS analysis of the runoff sediments indicated higher intensity of lignin-derived compounds in the BR treatment than in the RR and SR treatments. Polysaccharide-derived compounds, dominated by levoglucosan, tended to decrease over the growing season in all the treatments, and were lower in the BR treatment. Examination of a wide range of simulated agricultural effluents showed that short-term BOD measurements (BOD2 and BOD5) significantly correlated with TOC, POC, and dissolved organic carbon (DOC) (R2 = 0.62-0.77, P < 0.001), as well as to nitrite-N and total N (R2 = 0.45-0.66, P < 0.001), and improved relationships were obtained with multivariate regression analyses. However, these relationships weaken progressively with increasing incubation times. Application of bauxite residues, especially 2% of the neutralized red muds, significantly (P < 0.05) reduced the soluble P, organic C, heavy metals, and also the BOD of runoff water from manure-impacted soils. Overall, appropriate management practices and amendment techniques could improve water quality in selected agricultural systems.
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Udeigwe, Theophilus Kene, "Evaluation of management practices and remediation techniques for improving water quality in agricultural systems" (2008). LSU Doctoral Dissertations. 1313.