The Effect of Potassium and Calcium Concentration in the Nutrient Solution on Copper Toxicities in Vegetable Crops

Abstract

Bean, spinach, lettuce, and radish were grown in solution culture to investigate the effect of K and Ca concentration in the nutrient solution on Cu toxicities. Copper was supplied at levels of 0.02, 0.3, and 1ppm. At each Cu level K or Ca was supplied at rates of 2, 6, and 18me/l, Ca in Cu-K series and K in Cu-Ca series being supplied at 6me/l. The pH of the nutrient solution was adjusted to 5.
1. At the normal Cu level (0.02ppm), most crops showed the best growth at K 2 me/l and Ca 6me/l. The order of relative tolerance of vegetable crops to Cu was as follows: bean>radish>spinach, lettuce. In any crops, increasing the supply of Ca (2-18me/l) was effective in alleviating the growth reduction due to Cu 1ppm treatment. Increasing the supply of K (2→18me/l), however, exerted the similar effect only in radish at Cu 1ppm treatment.
2. In any crops, roots were found to accumulate a larger concentration of Cu than leaves, the difference being more marked where excess Cu was supplied. The excessive accumulation of Cu in roots was evidently suppressed by increasing the supply of Ca, but not always suppressed by that of K. In general, the Cu accumulation in roots was closely related to the growth reduction.