Date of Award
Master of Science
Intensified farming has led to concerns regarding the fate of applied nutrients especially nitrogen (N) and phosphorus (P). Phosphorus loss from agriculture fields has been linked to eutrophication of streams, rivers, and lakes, formation of hypoxic zones, and deterioration of economic services. In order to reduce these losses and promote sustainable uses of fertilizers, the agricultural community needs to explore more options to minimize nutrient losses while sustaining high crop yields. The purpose of this research was to evaluate different application rates of flue gas desulfurization (FGD) gypsum for reducing P losses in surface runoff and to determine the effectiveness of FGD gypsum for improving soil physical conditions and their impact on plant growth. Reductions in P losses have been documented from the use of FGD gypsum as a soil amendment in other mid-western states and regions like Ohio and Indiana, but more research is needed to identify it’s effectiveness in southern Illinois soils. This project was divided into two studies: a surface runoff study and yield plot study. The four treatments for the surface runoff study were as follows: gypsum at 2.24 Mg ha-1, gypsum at 4.48 Mg ha-1, gypsum at 13.45 Mg ha-1 and control (no-treatment). For the yield plot study, treatments were as follows: gypsum at 2.24 Mg ha-1, lime as a source of Ca at 1.65 Mg ha-1, elemental sulfur as a source of S at 0.5 Mg ha-1 and control (no-treatment). Both studies were under corn-soybean rotation. Surface runoff flumes were installed in summer 2018 at SIU Farms and yield plots were laid out in fall 2018 at SIU Farms and at field’s of two regional producers. Treatments were hand-applied at the runoff study site and a mechanical spreader was used at the yield plot site. Pre-treatment and post-treatment soil samples were collected in fall following crop harvesting at depth of 0-15 cm from yield plots and at 0-5 cm and 5-15 cm from surface runoff study. Surface runoff samples were collected after each significant rainfall event (≥12.5 mm) and runoff volume was measured. Soil bulk density, infiltration rates, penetration resistance, standard fertility analysis and crop yield were also compared among treatments. For the duration of this study (December 2018- January 2020), the mean annual precipitation and temperature were higher than the 10-year mean for the area. The event mean load and concentration values of dissolved reactive phosphorus (DRP) and total phosphorus (TP) reduced significantly in all gypsum treatments compared to control (p<0.1) during initial post-gypsum application period. This load reduction was attributed to binding of Ca in gypsum with soil P. Whereas, following fertilizer application DRP and TP values were not significantly different in treatments compared to control. However, there was no significant treatment effect on the mean concentration and load values of total suspended solids (TSS). No significances were found when analyzing corn yield among the treatments. There were no significant differences in soil bulk density and soil infiltration rate. Statistical comparison of pre-treatment and post-treatment soil fertility data in surface runoff study at 0-5 cm depth showed significant reduction in Mg in in all of the treatments and increase in S at 0-5 and 5-15 cm depth in treatments 4.48 Mg ha-1 & 13.45 Mg ha-1 compared to control. No significant difference was observed in Ca and Bray I P concentrations at two depths 0-5 cm and 5-15 cm. There was a significant change in Ca, S, Mg and Bray I P in the soil samples collected from yield plot study except S value in sulfur treatment only, which was significantly different from other treatments and control values. After one year of treatment application, mainly water quality was improved with reduction in TP losses from field and no other benefits such as improved soil physical properties, increased crop yield were observed. In the coming years, differences may occur as soil properties changes as gypsum continue to dissociate into the soil. Thus, this work presents evidence that soils with high STP levels could be amended with FGD gypsum to reduce P in runoff without any significant environmental consequences, such as heavy metal contamination. Therefore, use of FGD gypsum as a conservation practice needs to be thoroughly investigated at a larger scale and for a longer period.
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