A Method of Estimating Paddy Rice Culm and Internode Lengths from a Single Hill with Similar Average Number of Panicles

Abstract

In survey of paddy rice culm length, the longest culm is usually measured from the ground surface to the panicle neck node in a given number of rice plant hills sampled from sequential rows or from randomly selected test locations. A new method for estimating paddy rice culm and internode lengths from a single plant hill was devised in the course of yield assessment using Matsushima's method, which involves hills sampled five lines parallel to a diagonal one in a paddy field. A rice plant hill group with average number of panicles per hill was selected for yield assessment. Then a single plant hill to measure culm and internode lengths was selected from the either hill group having the average number of panicles per hill ± 1 panicle. The longest culm length of the population in the experimental plot was estimated with constant precision using the longest culm length or the average culm length of the measured hill. Therefore, this method provides a valid index comparable to conventionally measured longest culm length. The average culm length is particularly convenient for comparison among experiment plots regardless of different growth types N or N-1, i.e., difference in the pattern of internode elongation. In this assessment method, internodes of 2mm or longer were measured in 1 mm unit in all culms in a measured plant hill to calculate average internode lengths. Regardless of differences in years, cultivars and irrespective of classification by growth types, the population distribution of the average culm length exhibited normality. The respective internode lengths also showed a normal population distribution.