Studies on the sodium chloride injury of vegetable crops in relation to the form of nitrogen supplied and the calcium nutrition in sand culture

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Spinach and Chinese cabbage were grown in sand culture under glass and were supplied with NO3 (10m.e./l) or NH4+NO3 (5+5m.e./l) and with various Ca levels, both in the absence and presence of excess NaCl (100 millimol). The Ca levels used were: (a) 5m.e./l, (b) 5m.e./l plus foliar sprays (0.04M CaCl2, twice a week), and (c) 15 m.e./l, with CaCl2 being used as the Ca source. All of the solutions were adjusted to pH 6.2_??_6.4.1. In spinach, when no NaCl was added, it was observed that the favourable Ca level in the nutrient solution was higher with NH4+NO3 than with NO3 alone, and Ca sprays had a slight effect to increase the yield when nitrogen was supplied as NH4+NO3. In the presence of excess NaCl, however, both increasing concentration of Ca in the nutrient solution and Ca sprays were not effective and rather caused slight reduction of yield irrespective of the form of nitrogen supplied, and NO3 gave higher yields than NH4+NO3.In Chinese cabbage, the application of NH4-N and excess NaCl caused increased prevalence and severity of marginal rot on younger leaves, a symptom of calcium deficiency, which had detrimental effects on heading, yield and quality. To prevent the occurrence of this disorder, Ca sprays into the heart were remarkably effective in any case, but the increasing concentration of Ca in the nutrient solution had scaresely any effect.2. Contents of Ca, K or Mg in leaves were in antagonistic relations with Na or NH4. In spinach, Ca sprays or increasing concentration of Ca in the nutrient solution resulted in increased Ca content of leaves. In Chinese cabbage, however, Ca content of leaf blades of inner leaves was remarkably lower and less influenced by the treatments than that of outer leaves, and Ca sprays significantly increased the Ca content of leaf blades, while the increasing concentration of Ca in the nutrient solution had effect to increase Ca content of leaf blades only of outer leaves and rather decreased that of head leaves. And it was recognized that the Ca content or the Ca/N equivalent ratio in leaf blades of Chinese cabbage was closely related to the occurrence of the marginal rot.