Ionic Balance and Growth of Five Plant Species in Four Soils1

Abstract

AbstractThe concentration of organic anions or organic salts in plants was determined as the difference between the concentration of cations (Na+, K+, Ca2+, Mg2+) and the concentration of inorganic anions (Cl−, NO3−, H2PO4−, SO42−). The organic anion concentration in plants has been related with yield and the nutrient status of the plant in previous investigations. These reports suggested that a given plant species regulated the organic salt content within a narrow range of values at optimal growth rates. A normal organic salt content, the value observed at optimal growth, was postulated as one of the conditions for good growth. A low organic salt content was never accompanied by an optimal growth rate.In this study five plant species were grown in four soils at three levels of phosphorus in order to test these concepts for a wider range of conditions. The plants were grown in the greenhouse with presumably adequate levels of N, K, Fe, and Zn. A major interest was to compare the relation between yield and organic salt content of each species on the four soils at the highest nutrient level. With barley (Hordeum vulgare L.) the yield of dry matter increased as the organic anion concentration increased. With cotton (Gossypium hirsutum L.) and buckwheat (Fagopyrum esculentum) (with one exception) the yields and organic anion concentration were constant on the four soils. With sorghum (Sorghum bicolor) and pinto bean (Phaseolus vulgaris) the lowest yields were associated with the highest organic anion concentrations, which were above the normal values apparently because of some nutritional imbalance. With sorghum the nutrient imbalance appeared to be connected with low ratios of K/Ca and possibly with the lime content of the soils.