Studies on the Physical Characteristics of Rice Seedlings : I.Relationship between the physical characteristics and the injury of seedling on mechanical transplanting

Abstract

1. On mechanical transplanting using Mat-type seedling at the 4th leaf stage, it was observed that 11.0∼42.3% of the transplanted seedling sustained different types of injury by machines. The two common types of the injury were scratches on basal leaf sheaths and buckling of upper leaf blades: both of less significance to the yield. Less than 10% of transplanted seedlings suffered buckling and cutting at the basal part of seedlings, which has important effects on the plant growth after transplanting. 2. Close relations were observed between the injury (scratch, buckling and cutting) to the basal part of seedlings and the physical characters (buckling stress, modulus of elasticity, angle of buckling, plant height, buckling index and natural deflection ratio). This means that the injury is hard to occur to the short seedlings with hard and elastic leef sheaths and with erect, short leaf blades. 3. Three main characters, plant height, buckling index and natural deflection ratio, were selected as practical criterions of seedlings suited for mechanical transplanting. It is recommended for mechanical transplanting to prepare seedling shorter than 20∼22cm in plant height, less than 0.35∼0.40 in buckling index and less than O.15∼0.20 in natural deflection ratio