Studies on the absorption of nutrient elements in muskmelon. VI.

Growth injury on muskmelon as related to application of saline water and calcium

Abstract

1. In the previous paper the author reported that the growth injury on muskmelon which was observed at Iwata, Shizuoka Pref., is being caused by increasing of salt in the soil followed the irrigation of well-water containing much salts. However, it has not been cleared yet how much salts in irrigation water would be permissible for muskmelon culture. Some investigators have reported that salinity injury might be alleviated by calcium application to the soil. Therefore, a factorial experiment was settled combining five levels of NaCl concentration (0, 100, 250, 500 and 1, 000ppm) and two levels of calcium application(0 and 40g per plant).
2. As the NaCl concentration in the irrigation water was raised from 0 to 1, 000ppm, dry weight of the leaves, stem and roots, fresh weight of the fruit, soluble solids and external appearance of that, days from pollination date to fruit maturity, and N, P₂O₅, K₂O, CaO and MgO accumulations in the whole plant were markedly depressed. It is notable that the plants irrigated with 100ppm NaCl and without calcium application to the soil showed the growth injury symptoms such as the slight curling and marginal scorch of leaves, and the light browning of roots. The plants irrigated with 500 to 1, 000ppm NaCl, with or without calcium application to the soil, produced unsalable fruits which are light in weight and bad looking with undeveloped nets and yellowish coloration.
3. Exchangeable Na in the soil and electrical conductivity of that, Na₂O accumulation in the whole plant, and Na₂O and Cl concentrations in the leaves increased according as NaCl concentration of the irrigation water increased. While antagonistic relation was found between NaCl concentration in the irrigation water and SiO₂ concentration in the leaves which may be associated with transpiration. Na₂O, Cl and SiO₂ concentrations in the leaves in each plot, however, did not show any symptoms of excess or deficiency on the leaves. From these results, salinity injury on muskmelon seems to be caused by irrigation water containing much NaCl, which may result in retardation of absorption of nutrient and water.
4. When plants were irrigated with 0 to 250 ppm NaCl, calcium application to the soil (40g per plant) increased the dry weight of top and roots, and the fresh weight of fruit. Whereas, when they were irrigated with more than 500ppm NaCl, no effects were observed on them. It may be concluded, therefore, if the irrigation water contains more than 500ppm NaCl, the application of calcium as high as 40g per plant could not alleviate salinity injury on muskmelon.