IMPACTS OF FLUE GAS DESULFURIZATION GYPSUM APPLICATION ON AGRICULTURAL RUNOFF WATER QUALITY, AND CROP PRODUCTION. ASSESSING AGRICULTURAL RUNOFF WATER QUALITY, AND AGRONOMIC IMPACTS OF FGD GYPSUM APPLICATIONS IN SOUTHERN ILLINOIS

Author

Dipty Poudel, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2022

Degree Name

Master of Science

Department

Forestry

First Advisor

Williard, Karl

Abstract

Increasing world population and food shortages have put immense pressure on the agricultural industry for agricultural intensification and expansion. Inorganic nutrients, especially nitrogen (N) and phosphorus (P) are applied as fertilizers to produce higher yields. However, crops are generally unable to utilize all the applied nutrients and the excess nutrients can be exported into water bodies via leaching or surface runoff and contribute to eutrophication of waterbodies and hypoxia. Farmers and policy makers are seeking tools to reduce nutrient losses while maintaining high grain sustainable yields. The objective of this study was to evaluate the impacts of different application rates of Flue Gas Desulfurization (FGD) gypsum on phosphate export in surface runoff from agricultural fields and assess a time-series analysis of the impacts of different rates of FGD application on runoff volume and concentrations of dissolved reactive phosphorus (DRP), total phosphorus (TP), sulfate (S) and total suspended sediments (TSS). The study also aims to assess FGD gypsum’s impact on crop yield, soil physical properties, and soil chemical properties. Four different application rates of FGD gypsum were assessed for the surface runoff water quality study. Treatments were T1 (gypsum at 2.24 Mg ha-1), T2 (gypsum at 4.48 Mg ha-1), T6 (gypsum at 13.45 Mg ha-1), and Co (no gypsum applied or control). Twelve flumes with an area of 4.8 m (length) *1 m (width) were set up in an agricultural field under corn-soybean rotation in a completely randomized experimental design. There were 3 replicates of each treatment. Twelve plots were designed to collect surface runoff during rain events. Treatments were initially hand applied in December of 2018 (1st trt) which was followed by fertilizer application (NPK-based fertilizer) in 2019. Treatments were re-applied in December 2020 (2nd trt). No fertilization was applied after the second treatment application. This two-year study only incorporates results from February 2020 to December 2020 as post-trt one results that followed fertilizer application and from January 2021 to December 2021 as post-trt two results. Soil samples were collected both post-trt one and post-trt two to assess the soil physical and chemical properties.Post-trt one time period (February 2020- November 2020) includes twelve rain events and the results showed that runoff volume was reduced significantly (p < 0.1). Results showed no significant difference in DRP and TP concentration, but DRP and TP loads were significantly reduced (p < 0.1) in treatment plots compared to control. TSS concentration and loads were also significantly reduced in treatment plots in comparison to control (p < 0.1). SO4-S) concentration and loads significantly increased only in the T6 treatment plot in comparison to the control (p < 0.1). Post-trt two time period (January 2021- December 2021) includes twenty-one rain events and showed no significant difference in the runoff volume among treatments and control. There was no significant difference in the DRP concentration and loads. However, TP and TSS concentration and loads were both significantly reduced in treatment plots compared to control plots (p < 0.1). SO4-S concentrations and loads increased significantly in all gypsum treatment plots in comparison to control during post-trt two (p <0.1). Heavy metal analysis results showed that the gypsum did not add significant amounts of metals to the soil. Reduction in runoff volume, DRP loads, and TP loads was the greatest in T1 during the post-trt one. During post-trt two, the highest reduction in TP load was observed in T1. Time series analysis showed a significant trend of impacts of all three rates of FGD gypsum application on DRP and S concentration. While DRP concentration showed an increasing trend along with time in a 12 months window, S concentration showed a decreasing trend. Our results suggested that FGD gypsum’s effectiveness in reducing phosphorus loss can decline gradually within 12 months after application. The soil infiltration rate significantly increased with the increasing gypsum application rates during both post-trt one and post-trt two. Our observations suggested that the FGD gypsum can aid in reducing both runoff volume and phosphorus loss and can be an excellent clay flocculating agent. The yield quality study was conducted at three field-scale farms, which were under corn-soybean rotation. Four treatments were applied to the plots: Gypsum (gypsum at 2.24 Mg ha-1), Lime (lime as a source of Ca at 1.65 Mg ha-1), Sulfur (elemental sulfur as a source of sulfur at 0.5 Mg ha-1), and Control (no Ca or S treatment). The sulfur (S) and calcium (Ca) treatments were added at the same level of S and Ca as the gypsum treatment to understand the separate and combined impacts of S and Ca on agronomic quality. The experimental design was a completely randomized design and each treatment had three replications. Treatment was applied mechanically in 2018. Yield data were recorded annually from each treatment plot. Soil physical properties were assessed during the Fall of 2020 and 2021 for soil bulk density, water-stable aggregates, soil penetration resistance, and soil infiltration rate. Soil samples were collected for studying soil chemical properties and nutrient availability. From the compiled statistical analysis of 2020 and 2021, there was no significant difference in soybean yield, corn yield, soil bulk density, soil infiltration rate, and soil penetration resistance among treatments. Neither a positive nor a negative effect was observed on crop yield. Percent water-stable aggregates was found to be the highest in gypsum treatment followed by sulfur, lime, and control (p < 0.1). Treatments showed significant impacts on Mg, S, P, and Bray IP concentration. Mean soil Mg concentration was found to be the highest in lime treatment followed by gypsum, control, and sulfur. Mean soil S concentration was the highest in sulfur treatment followed by control, gypsum, and lime. Mean soil P concentration was found to be the highest in gypsum treatment followed by sulfur, control, and lime. Findings showed that the mean soil Ca, S, and P concentrations were increased, and mean soil Mg concentration was reduced in gypsum-treated plots. Study results suggested that the FGD gypsum has the potential to control surface runoff volume, phosphorus loading, and total suspended solids loading in agricultural surface runoff and amend soil physical and chemical properties. Results showed that the FGD gypsum didn’t have any statistically significant positive or negative impacts on the corn and soybean yield. Based on our findings, we conclude that the FGD gypsum can be an attractive agricultural practice to ameliorate water and soil quality in the context of southern Illinois. Long-term field-scale research can be done to evaluate the effects of FGD gypsum on crop quality more accurately.