Effect of Three Ca Sources Applied on Peanuts II, Soil Ca, K, and Mg Levels1

Abstract Field experiments were conducted on Kenansville lfs (Arenic Hapludult) in 1977 and on Rumford lfs (Typic Hapludult) in 1978 to compare two bulk-spread supplemental Ca sources with bagged landplaster. Bagged LP, 420 Landplaster Bulk (420-Bulk) and Texasgulf Gypsum (Tg Gypsum) were appplied on Florigiant peanuts (Arachis hypogaea L.) at rates equivalent to 260 kg/ha Ca broadcast and at three different dates: planting, early June just prior to flowering, and late June in early flowering stage. The relative effects of these Ca sources on changes in the contents of H2O- and 1.0 N NH4OAC-extractable soil Ca, Mg, and K in the 0- to 10-cm and 10- to 20-cm soil layers wre measured by analysis of periodic soil samplings taken during the peanut fruiting period. All three Ca sources increased the contents of both H2O- extractable Ca (H2O-Ca) and NH4OAc-extractable Ca (Ac-Ca) in both soil layers throughout the sampling period. In 1977, contents of H2O-Ca in treated plots often were 100 to 125 μg/g of soil higher in the 0- to 10-cm layer and 50 μg/g higher in the 10- to 20-cm layer than in untreated plots. Increases in the contents of Ac-Ca in treated plots up to 150 μg/g of soil occurred in several cases in the 0- to 10-cm layer and up to 100 μg/g in the lower layer. The Ca applications in 1977 increased the initial extractable contents of H2O-Ca and Ac-Ca more and the Ca persisted longer after Ca application than in 1978. Bagged-LP or Tg Gypsum generally increased the contents of H2O-Ca and Ac-Ca in the 0- to 10-cm layer considerably more than 420-Bulk, particularly in 1977. Differences between Ca sources often diminished with time after application of the materials. This occurred to a greater extent in 1978. The contents of Ac-Ca, particularly, in plots amended with 420-Bulk usually increased considerably toward the end of the sampling period. The contents of H2O-Ca and Ac-Ca in comparable samplings of the peanut fruiting layer generally were similar much of the time for all three times of applications. Changes in NH2OAc-extractable Mg contents extracted from the 0- to 10-cm and 10- to 20-cm layers following application of the Ca sources ranged from 10 to −25 and 28 to −22 μg/g of soil, respectively, in 1977. The ranges in 1978 were from 0 to −20 and 12 to −14 μg/g of soil, respectively. Similarly, changes in NH4OAc-extractable K in the surface and lower layers ranged from 10 to −25 and 13 to −18 μg/g of soil, respectively, in 1977. The ranges in 1978 were from 11 to −20 and 14 to −24 μg/g of soil, respectively. These contents of Ac-Mg and Ac-K decreased more frequently than they increased after application of the Ca sources, particularly when applied at planting. Relatively more increases occurred after the later application.