Magnesium deficiency in vegetable crops. A survey in Fujimi-mura and Showa-mura, Yamanashi Prefecture

Abstract

In those several years, vegetable crops production in Fujimi-mura and Showa-mura near Kofu, Yamanashi Prefecture has been threatened by a nutritional disorder, which seemed to be magnesium deficiency. The authors surveyed the symptoms and distribution of the disorder in vegetable crops in the area and attempted to elucidate its cause by chemical analysis of plants and soils. The disorder was found in many sorts of vegetable, such as tomatoes, egg-plants, peppers, cucumbers, melons, snap beans, radishes, chinese ca-bbages and leafy brassicas. Fruit trees and field crops also suffered from similar disorder in this area. The general symptoms were chlorosis of in-terveinal portions of lower leaves, subsequent ne-crosis of the chlorotic area, and in some crops premature defoliation. Yields were markedly reduced in severe cases. Those symptoms were very similar to the symtoms of magnesium deficiency artificially induced in sand culture in our laboratory or reported by other investigators. Further-more, low magnesium content in the affected tomato and egg-plant leaves, and low exchangeablemagnesium content in the soils, proved that the disorder was due to magnesium deficiency. Mg content was 0.35% or less in the affected tomato leaves, and was 0.25% or less in the affect-ed egg-plant leaves. Soils in the area were sandy, or gravelly and were very low in clay and organic matter content. Soil pH was from 5.09 to 7.95. Exchangeable capacities were generally low: most of them were 5_??_7m.e., but some of them were below 5m. e. per 100g soil. Exchangeable magnesium contents of deficient soils were less than 0.5m.e. per 100g soil. No case of magnesium deficiency due to high level of potassium was found. From those results, it was clear that the magnesium deficiency of the vegetable crops in this area was due to low content of available magnesium in the soil. As control measures, soil and foliar applications of magnesium compounds were discussed. There were differences among vegetable crops in susceptibility to magnesium deficiency. Furthermore, varietal difference was found in resistance to the disorder in some crops.