Stubies on the nutrition of the rice plant in relation to the occurrence of the so-called "Akagere" bisease : I. Occurrence of the disease as influenced by the temperature of the irrigation water anb by the supply of potassium or starch to the soil

Abstract

Rice plants were grown on the soil of a pabby field where habitual occurrence of the "Akagare" disease was seen. Different conditions were given to the plants as regard to the temperature of the irrigation water and supply of potassium or starch to the soil. The results of the experiment are as follows:- (1) Depletion of potassium, supplying starch to the soil, and exposing the plant to warm irrigation water (36-39°C) without potassium supply, all caused retarded growth both in the top and in the root, resulting in increased affection by the disease. (2) Supplying starch to the soil increased the per cent content of FeO, and decreased the content of K₂O, MnO and especially, soluble MnO in the plants. The soluble-N/protein-N ratio of the leaf blade was increased by the same treatment. (3) The Eh value of the expressed shoot sap was lowered both by depletion of potassium and by application of starch. (4) The occurrence of the disease seemed to be highly correlative to the decrease of K₂O/N ratio in the leaf blade.