Maize growth and mineral acquisition on acid soil amended with flue gas desulfurization by-products and magnesium

The large amounts of coal combustion by-products (CCBs) generated by coal burning power plants must be utilized or discarded, and beneficial use of these materials are desired. One beneficial use of CCBs could be application to agricultural land. Information about the use of one kind of CCB (flue gas desulfurization by-product, FGD-BP) on soil is limited. Maize (Zea mays L.) was grown (greenhouse) on an acid soil [Umbric Dystrochrept, pH(Ca) (1:1, soil:10 mM CaCl2) 4.2] amended with two high CaSO4 FGD-BPs (5 and 15 g . kg(-1) soil) and CaCO3 (2.5 and 5.0 g . kg(-1) soil) at varied calcium/magnesium (Ca/Mg) equivalency ratios (0/0, 1/0, 1/0.01, 1/0.05, 1/0.1, and 1/0.5) to determine treatment effects on growth traits [shoot and root dry matter (DM) and total and specific root length (RL)], mineral concentrations in leaves, and soil pH and electrical conductivity [(EC) 1:1, soil:water]. Magnesium deficiency symptoms were induced on leaves of plants grown with and without low Mg, and the Mg to Ca ratio in each amendment needed to be about 1 to 20 to alleviate Mg deficiency. Shoot and root DM and total RL of plants grown with FGD-BPs became higher as Mg increased. Specific RL (total RL/root DM, root fineness) was not affected by FGD-BP and only slightly by Ca/Mg ratio. Shoot concentrations of Mg increased; Ca, phosphorus (P), and manganese (Mn) decreased; and potassium (K), sulfur (S), iron (Fe), zinc (Zn), and copper (Cu) remained relatively constant as amendment and Mg increased. On unamended soil, aluminum (Al) and Mn concentrations in shoots were above normal. Enhancement of growth was closely related to increased soil pH compared to added Mg for CaCO3 amended soil and to increased Mg compared to increased soil pH for FGD-BP amended soil. Except at the highest level of Mg where soil pH increased, added FGD-BPs and Mg had only limited effect on increasing soil pH. Soil EC increased from added FGD-BPs but not fi om added Mg, and EC was not sufficiently high to be detrimental to plants. Maize grown on this acid soil amended with FGD-BPs received benefits when caution was used to alleviate mineral deficiencies/toxicities inherent in the soil.