Effect of Potassium and Calcium Levels and their Accompanying Anions in the Nutrient Solution on Ammonium Toxicity in Vegetable Crops
1982 Volume 51 Issue 3 Pages 309-317
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1982 Volume 51 Issue 3 Pages 309-317
Using water culture, a study was made on the effect of K and Ca levels in the nutrient solution on ammonium toxicity in vegetable crops. Materials used were sweet corn, cucumber, kidney bean, lettuce, cabbage, Chinese cabbage, and spinach. Nitrogen was supplied as NO3, NH4, or NO3+NH4(1:1) at N levels of 12me/l, which was combined with K or Ca levels of 2, 6 and 18me/l, respectively. The pH of the solution was adjusted to 6.0. Plants were grown in the different treatments for about 3 weeks. In another experiment, lettuce and spinach were grown in order to compare the effect of chlorides, carbonates, sulphates, and silicates of K and Ca in the solution on ammonium toxicity.
1. Regardless of the kind of vegetables, the growth of plants fertilized with NO3 +NH4 was almost equal to, or better than that of NO3 fertilized plants. When plants were cultured with NO3 or NO3+NH4, the level of K or Ca in the solution had a great influence on the concentrations of these elements in leaves but had almost no influence on the growth of plants.
As compared to NO3, NH4 nutrition decreased the growth of all vegetables except sweet corn, and lowered the concentrations of K and Ca in leaves of all vegetables. The concentrations of K and Ca in leaves increased with increasing K and Ca levels in the solution, respectively. Under NH4 nutrition, increasing K level in the solution alleviated the growth reduction only in tomato and kidney bean. Increasing Ca level in the solution also alleviated the growth reduction only sweet corn, cucumber, lettuce, and cabbage. In both cases, however, the alleviation was so small that the growth of NH4-treated plants was much inferior to that of NO3-treated ones except sweet corn.
2. Even under NH4 nutrition, the pH of the nutrient solution was kept rather high for a long period after the application of carbonates or silicates of K and Ca. This effect was especially remarkable for CaCO3. In all cases, however, NH3 toxicity in lettuce and spinach was hardly reduced.
