On the fertilization and cultivation of horticultural crops under covering conditions II. On the high-salt injury of vegetables

(2) Growth and mineral nutrition of fruit crops under heavy fertilizer application

Abstract

Experiments were conducted to elucidate the effects of a) the higher concentrations of he nutrient solutions and of nitrogen in the substrate, and b) the sources of nitrate nitrogen, both on the growth and chemical composition of several fruit vegetables such as cucumbers, eggplants, tomatoes and peppers.
1. Growth retardation was observed when the plants were grown in nutrient solutions held at higher levels. Cucumbers were the most sensitive to high nutrient solutions, followed by peppers and tomatoes, and eggplants were suppressed in growth in those media to a lesser extent. It seems therefore that eggplants have a relatively higher ability to tolerate the higher concentrations of the growth medium.
2. An increase in potassium contents in the leaves and a decrease in calcium contents in the upper leaves were observed as the concentration of nutrient solutions became higher.
3. Plants were grown in the media raised nitrate concentrations with NaNO₃, or Ca(NO₃)₂. Order of susceptibility among the species tested to higher nitrate nitrogen levels in the media was the same as that observed in the experiment with the nutrient solution. Growth of cucumbers was severely restricted by high nitrogen of media. Eggplants were resistant to it. Retardation of growth of peppers was more remarkable than that of other crops when the nitrogen concentrations were raised with NaNO₃.
4. A decrease in the contents of potassium, calcium and magnesium in the leaves was observed in all crops when grown in the higher NaNO₃ media. Especially the magnesium content of eggplant leaves was greatly decreased by the heavy applications of NaNO₃.
5. Magnesium contents also decreased both in the leaves and in the stems of eggplants and cucumbers under heavy applications of Ca(NO₃)₂, but decreased only in the stems as regards tomatoes and peppers.
6. The plants were grown in the standard nutrient solutions to which nitrate salt of ammonia, potasium and calcium was added separately at the rate of 30mM/l. An increase of growth was found in cucumbers and tomatoes grown in KNO₃-added media. Growth of tomatoes was greatly decreased in NH₄NO₃-added solutions. It was evident that applications of ammonium nitrate to the standard nutrient solutions decreased the content of calcium in the aerial portions of tomato plants.