Managing soil acidity vs. soil Ca:Mg ratio: What is more important for crop productivity?

摘要

Soil balancing (SB), or base cation saturation ratio (BCSR), is a soil management approach that strives to maintain specific soil calcium (Ca) and magnesium (Mg) levels to improve soil health, decrease pest problems, have better crops, and increase crop yield. To achieve ideal levels of Ca to Mg, BCSR practitioners apply gypsum (calcium sulfate) and high-calcium lime (Hi-Cal lime) amendments, with the former increasing Ca base saturation and the later increasing both Ca base saturation and soil pH. We hypothesized that positive benefits ascribed by BCSR practitioners are due to increasing soil pH, rather than increasing Ca levels, both of which occur after lime application. Thus, we conducted successive applications of gypsum or epsom (magnesium sulfate) with and without Hi-Cal or dolomitic lime, to either increase or lower soil Ca:Mg ratio and pH in an Ohio-based experiment over 6 yr and evaluated soil and yield responses in a corn (Zea mays L.)-soybean (Glycine max L.)-small grain rotation. Repeated applications of gypsum with and without Hi-Cal lime significantly increased soil Ca:Mg ratio and repeated applications of epsom with and without dolomitic lime significantly decreased the soil Ca:Mg ratio. Crop yield was not affected by soil Ca:Mg ratio for any crop in any year. However, over the 6 yr of the study, corn yields were positively related to increases in soil pH. We conclude that balancing soil Ca and Mg levels did not impact corn or soybean yields but managing soil acidity remains a fundamental tool to improve crop yields.