Liming for peanuts in relation to exchangeable soil calcium and effect on yield, quality, and uptake of calcium and potassium

In a series of lime experiments on sands and sandy loams, which ranged in exchangeable Ca content calculated as CaCO3 equivalent from 160 to 1,241 pounds per acre, the critical level of exchangeable Ca in unlimed soils for Spanish and runner peanuts was found to be in the range of 600 to 800 pounds per acre. With one exception, soils containing more than the equivalent of 700 pounds of CaCO3 per acre showed only slight increases in yields for lime: whereas soils containing less than 600 pounds per acre gave highly significant increases. It is highly probable that over 50% of the soils in southern Alabama now used for peanut production contain less than the critical amount of exchangeable Ca. Data are presented showing that the relationship between the amount of exchangeable Ca in the soil and lime response is close enough to justify the use of lime on the basis of amount of exchangeable Ca present. Ten sources of lime were compared on Norfolk sand at 1,500- and 3,000-pound per acre rates. All of the high Ca sources were about equal in value except two Ca silicate slags which gave profitable increases over no lime but were inferior to the other liming materials, on a pound-for-pound basis. Dolomitic limestone was superior to high Ca lime on intensively cropped Norfolk sand but was not significantly better in larger scale field tests on sandy loam soils of the same series. Although 4 years after application of 1,500 pounds of limestone there was no residual effect on soil pH, this application produced from 900 to 1,500 pounds of peanuts more than unlimed plots in an intensive cropping experiment. Thus, the major beneficial effect of lime on peanuts appears to be the supplying of Ca and Mg as plant nutrients. This was substantiated by a marked lime-fertilizer interaction in which response to lime was less when commercial fertilizers carrying appreciable amounts of Ca were used. Lime improved the quality as shown by increased shelling percentage of runner peanuts when grown successively for several years on the same soil. A high rate of K fertilization (120 pounds of K2O per acre) decreased the shelling percentage of sound and mature kernels as much as 8% on one field. The addition of lime to peanuts decreased markedly the percentage of K in the vines the decrease ranging from 30 to 46%. This reduction in K content of peanuts by liming a Ca-depleted soil was attributable, in part, to increased growth and increased the efficiency of utilization of applied K from 27 to 73% by Spanish peanuts. Similarly, lime increased the utilization of K by runner peanuts from 42 to 85%. It was shown that the peanut is a crop which can tolerate a high Ca:K ratio and possesses an ability for luxury absorption of K far in excess of that required for normal growth.