Growth and Ca Uptake by Plants as Affected by Rate and Depth of Liming

Abstract The study involved the liming of two acid soils, one high in extractable Al and one of similar pH, but low in extractable Al. Portions of each soil were treated in the laboratory with Ca(OH) 2 (labeled with Ca 45 ) to bring the pH to three levels. One of the soils also had been maintained in the field at the same pH levels for many years. Three depths of topsoil were used with corresponding depths of subsoil. These soils were placed in 18‐inch cylinders and cropped to alfalfa. Results indicated that plant yields, root proliferation, and consequent uptake of Ca depend largely on adequate level of lime in both topsoil and subsoil. However, if sufficient lime was applied to the topsoil, near maximum yields were obtained regardless of the lime level of the subsoil. Subsoil liming had minor effects on yield and uptake of Ca except when the topsoil was shallow and more acid. The soil with the highest level of Al responded proportionally more to the lime added. Freshly added Ca appeared to be more available to alfalfa than Ca added earlier in the field. The percentage of Ca from the topsoil‐applied source increased from 8 to 100% as the rate of liming increased from ½ to 8 tons per acre in a 3‐inch layer of the most acid soil. With increased level of lime in the subsoil, smaller percentages came from the Ca applied to the topsoil. Root growth generally reflected what yields and Ca uptake had indicated. Root cation‐exchange capacities increased with increased rate of liming.