Studies on the Pysical Characteristics of Rice Seedling : III. The Effect of Potash Application

Abstract

To obtain suitable seedlings for mechanical transplanting, the effect of potash application was studied on the physical characteristics of seedlings at the 4th leaf stage. Zero to four g/box of potash (K₂O) were applied as basal dressing to the seedlings grown in seedling boxes, which were filled with Kitamoto (K-deficient) and Konosu (standard) soils. 1. Physical characters of seedlings differed significantly by the difference in soils and by the amount of potash applied. Comparing with the seedlings grown in Konosu soil, those grown in Kitamoto soil were more rigid in the structure of basal part, thicker in basal section and more resistant to buckling and bending, which were due to the well developed basal part with erect and short foliage. A decrease in the rigidity in the basal part was observed as potash application was increased (Fig. 1). 2. Potash content in leaf sheath was closely related with the nature of soils and the amount of potash applied. High potash content was observed in the seedlings applied more amount of potash and this case was observed a also in the seedlings grown in Konosu soil. An increase in potash content resulted in the reduction of structural rigidity in basal part, with the increment in basal section diameter. This means that the resistance to buckling and bending decreases because of excessive foliage grown with poor developed basal part (Fig. 2). 3. So far as the information presented, no relations have been found between abundant potash application and the vigour of seedling. Therefore it is concluded that excessive potash application is not recommended because of the unfavorable physical characteristics for mechanical transplanting.