Calcium nutrition of vegetable crops. II

Abstract

Because of the fact that there were recently found nutritional disorders of Chinese cabbage which seemed to be due to calcium deficiency, in some areas, several experiments were carried out by means of water culture to clarify symptoms of cal-cium deficiency in Chinese cabbage and also to elucidate the effect of composition of culture solution on its occurrence. 1. Symptoms of calcium deficiency in Chinese cabbage: When appear before heading, the tip mar-gins of green leaves show water-soaked and trans-parent appearance, then rapidly wilt and collapse into dehydrated white band. This symptom is the same as the so-called Fuchigusare (marginal rot) found in the field. Both troubles can be prevented by the spray of calcium salt solution. Consequent-ly, Fuchigusare has been proved to be due to calcium deficiency. When calcium is deficient after heading, the mar-gins of head leaves become water-soaked like and transparent, then turn light brown and soft-rot due to the secondary invasion of rot bacteria. As to the identification of Shingusare (heart rot), the occurrence of which is rather prevalent and more serious than Fuchigusare, the similarity of its symp-tom with that of calcium deficiency after heading, the low calcium content of rotted leaves as well as the observations on the conditions of its occurrence show the possibility that it is due to nothing but calcium deficiency in spite of the failure of cal-cium spary to prevent it. 2. Low calcium concentration, high salt concen-tration of medium and NH4 used as a part of ni-trogen source, all of these decrease calcium absorp-tion by the plant, and this decrease is responsible for the appearance of calcium deficiency. Calcium content of head leaves, however, is markedly low even in the normal plant irrespective of its high content in the lower, green leaves. Moreover it does not necessarily reflect closely the decrease ofcalcium absorption on the whole, especially when analysis is made including midribs. 3. NH4 used as a part of nitrogen source decreas-es the absorption of calcium, magnesium and potassium, and increases that'of nitrogen and phos-phorus by the plant. Under high salt concentration as a whole, the absorption of calcium as well as of magnesium de-creases consistently regardless of the simultaneous increment of them in the medium, while the ab-sorption of nitrogen and phosphorus does not show any definite trend andthat of potassium is much influenced by K/N ratio in the medium, that is, decreases following low K/N and increases follow-ing high K/N. 4. The echanism of decreased calcium absorp-tion in relation to the occurrence of calcium deficien-cy in the field and pot culture and also the pecu-liarity of calcium deficiency symptoms were discus-sed.