THE AVAILABILITY TO PLANTS OF DIVALENT CATIONS IN THE SOIL

Methods for characterizing the equilibrium soil solution are described and are applied to experiments in which soils used in pot culture experiments were labelled with Ca/sup 45/ and Sr/sup 89/. Six soils showing a wide range of characteristics were used. In all soils the ratio of Sr/sup 89/ to Ca/sup 44/ or to stable calcium in the equilibrium solution was less than the ratio of exchangeable Sr/sup 89/ to Ca/sup 44/ or to stable calcium. The extent to which the ratios differed varied between soils. Three of the soils contained calcium carbonate which somewhat complicates the interpretation. Moreover, when calcium hydroxide was added to these soils varying amounts of calcium carbonate were precipitated. When this occurred after Ca/sup 45/ had been added, some of it was precipitated with Ca/sup 40/. The ratio of strontium to calcium absorbed from soil by barley and cabbage showed reasonable agreement with that observed when the plants were grown in nutrient solutions similar in composition to the equilibrium soil solution. (auth)