Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/7/2004
Publication Date: 11/15/2004
Citation: Ritchey, K.D., Belesky, D.P., Halvorson, J.J. 2004. Soil properties and clover establishment 6 years after surface application of ca-rich by-products. Agronomy Journal 96:1531-1539. Interpretive Summary: Liming is important to establish and maintain low-acidity conditions in soils so that forage plants can grow well. Mechanical incorporation of limestone in hill lands can lead to soil loss. An alternative is to surface-apply calcium sources that are more soluble such as coal combustion by-product (CCB) gypsum. Gypsum is known to improve grass yield on acid soil for several years after application, but we do not know how long the benefits last, and soil sampling techniques for surface applied amendments are not well-worked out. We surface-applied limestone and several CCB materials to an acid Appalachian site and, after 4 years of grass production, overseeded with clover. Soil changes 6 years after application of 2 tons/acre limestone were concentrated in the surface inch. Soil improvements due to gypsum were less than those resulting from limestone addition. All the amendments reduced soil acidity, and clover-grass hay yields in the sixth year increased ad soil acidity decreased. The residual effects of application of CCB gypsum 6 years after application showed little benefit for grass-clover production apart from reduction in acidity due to a small (5%) calcium carbonate component in the by-product. Where gypsum had been applied by itself with no magnesium source, magnesium deficiency reduced yields, but use of calcium-magnesium limestone or magnesium oxide fertilizer overcame this problem. Yields were more closely correlated with properties of soil samples collected from the surface inch than from deeper samples.
Technical Abstract: Calcium-rich soil amendments can improve plant growth by supplying Ca and reducing detrimental effects of soil acidity, but solubility and neutralizing capacity of Ca sources vary. Calcium and Mg soil amendments were surface-applied to an abandoned pasture in 1993 and orchardgrass (Dactylis glomerata), bluegrass (Poa pratensis) and tall fescue (Lolium arundinaceum (Schreb.) Darbyshire) were sown in 1994. Six years after application, reduction in soil Al and Mn and increases in Ca and pH from dolomitic limestone, fluidized bed combustion residue, and MgO fertilizer were greatest in the surface 2.5 cm, while high rates of gypsum application left little residual effect except for decreases in Mg. Plots were split to accommodate interseeding in spring of 1998 with red clover (Trifolium pratense) or white clover (T. repens), as well as a non-seeded control. No N fertilizer was applied after interseeding. Percentage clover in the sward increased as soil acidity decreased as a function of increasing CaCO3 equivalent of amendments. Subsequent herbage yield increased as a function of legume increase. Where high gypsum application decreased soil Mg levels, yields fell. Yields were more closely correlated with properties of soil samples collected from the surface 2.5 cm than from deeper samples.