UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Influence of FGD gypsum on the properties of a highly erodible soil under conservation tillage
Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 11, 2011
Publication Date: N/A
Interpretive Summary: The success of conservation tillage management systems imposed on highly erodible soils is, in large part, dependent upon practices that stabilize the soil surface, improve infiltration and soil water storage capacity, ameliorate acidity problems, and provide an adequate supply of essential plant nutrients. The application of lime and fertilizer amendments to soil surface in no-till systems can be less than adequate due to the excess time required for slowly soluble agricultural lime to dissolve and stabilize soil physical properties to the extent that water and nutrients can more rapidly move into and down the soil profile. As an alternative to agricultural lime, we used fluidized gas desulfurization (FGD) gypsum, a byproduct of coal-fired power plants, due to its high calcium and sulfur contents, and its much greater solubility than lime. We applied FGD gypsum to no-till cotton on a highly erodible loess soil at rates of 0, 1, 2, and 3 tons/acre for three years, and monitored changes in soil properties as a function of amendment rate, depth, and time. The data showed that within one year of initial application, significant increases were recorded for calcium and sulfur contents at depth which lead to substantial increases in soil stability and decreases in aluminum toxicity. Cotton plant uptake of the essential nutrient also increased significantly during the study period. The results indicate that FGD gypsum can potentially increase yields of no-till cotton by improving soil water conditions and providing a readily available source of sulfur, a limiting nutrient in many cotton soils.
The performance of conservation tillage practices imposed on highly erodible soils may be improved by the use of amendments with a high solubility rate, and whose dissolution products are translocated at depth in the soil profile faster than normally used agricultural lime and fertilizer products. This study was conducted to determine the time required, and effectiveness of surface-applied FGD gypsum at increasing calcium and sulfur contents at a range of soil depths for improvements in aggregation and sulfur status. Fluidized gas desulfurization (FGD) gypsum was surface-applied at four rates (0, 2.24, 4.48, and 6.72 Mg ha-1) for three years to experimental field plots established on a farmer-operated field planted to no-till cotton (Gossypium hirsutum L.). Soil samples were collected one year after initial application at depths of 0 to 10, 10 to 20, and 20 to 30 cm, and after three years at depth increments of 0 to 10, 10 to 20, 20 to 30, 30 to 46, and 46 to 61 cm. The fine earth fraction (< 2mm) of these soils were characterized for particle size distribution, water dispersible clay (WDC), aggregation index (AI), exchangeable Ca and Al, total C, N, and S, electrical conductivity (EC), and pH. Leaf tissue samples were collected from the cotton plants at approximate mid-bloom stage and characterized for total C, N, and S. The soil data showed that significant (P < 0.05) increases occurred in the Ca and S contents at depth in one year which increased the AI and reduced the exchangeable Al activities in the subsoil. Plant uptake of S increased significantly as a function of amendment rate. These results indicate that FGD gypsum can increase crop yields through its ability to contribute to: increased infiltration and soil water storage capacity, reductions in runoff losses, amelioration of exchangeable Al problems, and increased soil S contents.