Response of rice varieties to the application of ammonium sulphate and to the spacing of plants.

Abstract

1. According to the yield records of two years (1947-48), varieties of different plant-types responsed to the dressing and spacing in the following ways. V.1 (Yashima-senbon), V.3 (Ginbozu-midashi), V.4 (Norin-22) and V.7 (Kanto-9) belonged the 1-group (suitable for heavy fertilizing), V.2 (Tamanishiki), V.5 (Sady Wright) and V.6 (Boshito-chinese rice) to the 2-group (suitable for less fertility), and V.3, V.4, V.5 also suited to sparse spacing (the 3-group) while V.1, V.2, V.6 and V.7 suited to dense spacing (the 4-group). 2. (a) As to the response of the varieties to the application of ammonium sulphate, the yield increase was not always in proportion to the increase of the total nitrogen absorbed by the plant, but it was rather connected with the efficiencies of a unit amount of nitrogen absorbed by the plant to produce the paddy grains. (b) While, the yield increase of varieties in the case of narrow spacing of plants was highly correlated with the increase of nitrogen content in plants. 3. (a) In the heavy dressed field the amount of nitrogen in plants of the 2-group increased more notably in the early stages atter transplanting, and at the same time, the soluble nitrogen content per total nitrogen increased more remarkably. As the result of it, the capacity of absorbing new nitrogen in the later stages became lower as compared with none dressed field. But this inversion time differed with variety. (b) Varieties in the 2-group had smaller nitrogen content per total dry matter in plants in the vegetative growth stage than the 1-group, and they lost rapidly to assimilative ability of their leaves after heading. They also showed more lodging. 4. Varieties in the 3-group have an ability to absorb anew much amount of nitrogen during the following period, in proportion to the amount of nitrogen that have been already absorbed into the plant. They showed less content of nitrogen per unit area of living leaves, and showed higher content of ammonium nitrogen per fresh matter in plants, as compared with the 4-group. 5. Some theoretical considerations were given to the results above mentioned.