Citrus Tree Growth and Fruit Production Response to Flue-Gas Desulfurization Gypsum Amendment in Sandy Soils

Abstract

Widespread acceptance of industrial by-products as agricultural soil amendments depends on research data to support their benefits in terms of crop growth, production or quality, and demonstration of no adverse effects on the quality of crops, soils, and/or groundwater. The sulfur dioxide scrubbing process during coal burning to minimize atmospheric emission from coal-fired electric power generation plant produces high duality calcium sulfate (gypsum), called flue-gas desulfurization gypsum (FGDG). Since FGDG contains no toxic elements and is a good source of calcium (Ca) and sulfur (S), it maybe beneficial as an amendment to agricultural soils. Alternate beneficial use of this produce minimizes the demand for landfill space, which is quite expensive and may raise environmental concerns. Effects of FGDG amendment to sandy soils on citrus tree growth, fruit production, and fruit quality in four field experiments were evaluated. FGDG contained low levels of Ra-226 (<0.3 pCi g(-1)), so application of FGDG at 4.48 Mg ha(-1) did trot increase Rn-222 emission compared to the background levels from unamended soil. In a two years study, application of 4.48 Mg ha(-1) FGDG significantly increased fruit yield as well as soluble solids in the fruits. Application of FGDG significantly increased the concentration of Ca in Leaves in one location that had low Mehlich 1 or Mehlich 3 extractable soil Ca. At the rates of FGDG used ill this study, there were no apparent antagonistic effects of increased Ca application on the availability and uptake of K or Mg. Accordingly supplemental application of potassium magnesium sulfate had no additional effects on tree growth, leaf mineral concentration, or fruit yield and juice quality. This study demonstrated benefits of FGDG at rates up to 4.48 Mg ha(-1) for increasing the citrus fruit yield and fruit quality in sandy soils that contain low levels of extractable Ca. These results are encouraging for use of FGDG in citrus groves located in low-Ca sandy soils.