Researches on the Technical Improvement of Rice Culture on Ill-Drained Fields.

[摘要] (1) 31 samples of "Akagare" paddy fields and 17 of ordinary paddy fields were examined comparatively. Nitrogen and humns contents, effects of the drying treatment of soil, soil reduction, obsorptive coefficients of K2O or NH3-N of each soils ete. were measured. As the results, we found that the factors inducing the Akagare disease would be a poor natural supply of potassium, abundant humus contents in the ill-drained fields, want of ferric substances in the surface soil, excess of ammonium nitrogen, deficiency in oxygen, promoted reduction of Eh value, harmful substances such as organic acid (butyric acid), ferrous compounds, or hydrogen sulphide in the soil. 13 different types of Akagare paddy field were classified according to the factors ascribable. (2) For the purpose of studying the influences of reductive soil conditions on the plant growth, pot experiments were carried out. In the non-aerated plots, the surface of the soil in the pots were covered with olive oil at various stages of plant growth. In the plot II, the soil being covered with oil during the tillering stage, symptoms of "Akagare" disease were found on the upper parts of leaf-blade, and contents of total-N, Fe++ and SO3 in the plant were very much in comparison with, those in the cortrol plot plants, while K2O/N ratio was lower. In the plots IV or V, covered duriug from the ear-forming to the heading stage, the plants grew normally. (3) Influences of harmful substances such as H2S, butyric acid, or ferrous compounds on the vitality of roots and the nutrient absorption, were investigated by a solution culture experiment. Actual injuries of those harmful aubstances added to the solution were observed to be as follows: (a) Prohibition in elongation of roots and in tillering. (b) Decline in water absorption and in consumption of O2 of the roots. (c) Hindrance of absorption of nutrients such as K2O and NH3-N. Consumption in the roots occurred remarkably at the tilleriug and the ear-forming stages, respectively. Symptoms of "Akagare" disease were observed clearly at the tilleriug stage by applying H2S (60 p.p.m) and butyric acid (1/50 N) to the solution. Nutrieut absorption and vitality of the roots recovered 2 to 3 weeks after the removal of those harmful substances from the solution.

[学科分类] 农业科学（综合）