Effects of Seeding Density per Seedling Box and Planting Density on Production Cost of High-yielding Rice Varieties in Ishikawa Prefecture

Abstract

Production costs per unit area in rice cultivation can be lowered by reducing the number of seedling boxes either by increasing the seeding density per box or by decreasing transplanting density. The decrease in the number of seedling boxes, however, may lower grain yield and therefore may not reduce production costs per grain yield as much as expected. The objective of this study was to clarify the seeding density per seedling box and transplanting density that, when used together, minimize the production costs per grain yield in high-yielding cultivars “Ishikawa 65” and “Hokuriku 193”. In the 3 years from 2016 to 2018, we grew these cultivars at various seeding densities and transplanting densities, investigated their growth, yield and yield components, and calculated the production costs per grain yield based on the number of seedling boxes used. Grain yield was significantly smaller at the lower transplanting density but was not significantly affected by seeding density. The cost per grain yield was the lowest, when the density of seeding was 300 g per box and the density of transplanting was 21.2 hills per square meters, which required 9.2-9.8 seedling boxes per 10 a. The grain yield was highly correlated with the number of stems and growth index (the number of stems × plant height × SPAD Value) at the active-tillering stage in both cultivars.