Amelioration of an Acid Soil Profile through Deep Liming and Surface Application of Gypsum

Abstract

Highly weathered soils in the southeastern USA often have very acid, hard, infertile subsoils not readily penetrated by crop roots. An experiment on a Typic Hapludult involving deep liming, subsoil disturbance and mixing, and surface application of gypsum was conducted to investigate the possibilities of ameliorating such subsoils. Results with alfalfa (Medicago sativa L.) over 4 yr show that liming to 1 m can increase yields by 50% while merely mixing the subsoil without lime incorporation resulted in a substantial yield decline. Surface application of gypsum with sufficient time for it to penetrate the subsoil resulted in 25% yield increases. Deep liming resulted in the complete precipitation of soluble Al and increased the level of soluble Ca allowing roots to freely penetrate the subsoil. Gypsum resulted in a progressive reduction in soluble Al and an increase in soluble Ca creating a similar but lesser effect than liming. Water extraction patterns corroborated the fact that roots were penetrating chemically ameliorated subsoil. Saturation extract studies indicated that gypsum reduced the activity of Al3+ and increased that of Ca2+ substantially. These results suggest that by‐product gypsum from phosphate acid manufacture would be a feasible amendment for acid subsoils.

Land application of spent gypsum from ditch filters: phosphorus source or sink?

“…mineralogy dominated by 2:1 minerals). This occurs mainly from a ligand exchange reaction of sulfate with terminal hydroxyl groups on variable charged minerals which releases a hydroxide to solution [21,22].…”

Impact of a New Deep Vertical Lime Placement Practice on Corn and Soybean Production in Conservation Tillage Systems

“…Effects of subsoil acidity on agronomic production is of great concern in multiple regions around the world [1][2][3][4][5][6], with roughly 70% of the world's arable land having some level of soil acidity [7]. Acidic conditions in the subsoil horizons have been shown to affect nutrient availability and root growth of many agronomic crops [2,8,9].…”

“…Amendments of agriculture limestone have the ability to alleviate soil acidity [1][2][3][4][5][6]12,13]. Liming additions have been shown to increase grain yields of many crops through increased rooting systems, nutrient availability and uptake, drought resistance, and reduction of aluminum and manganese toxicities [1,4,5,14].…”

“…Liming additions have been shown to increase grain yields of many crops through increased rooting systems, nutrient availability and uptake, drought resistance, and reduction of aluminum and manganese toxicities [1,4,5,14]. In the United States alone, it is estimated that roughly 73 million Mg of agricultural lime is required each year to neutralize acidity generated from crop removal [15].…”

“…Treatments of lime increased rooting depth, plant height, and grain yield for corn [20]. Sumner et al [1] found a 50% increase in alfalfa (Medicago sativa L.) yields when lime was incorporated with a moldboard plow to a 1 m depth over a 4-year period. However, effects from soil mixing alone significantly decreased yields.…”