Adaptability of dry weight rank method for botanical analysis of natural pasture grown in coconut plantations

Abstract

The objective of this study was to find out the relationship between dry weight rank method (DWRM) values and hand separation (HS) values in order to determine the accuracy and validity of DWRM to study the botanical composition (BC) of tropical pastures grown under coconut. The species which came first, second and third place in terms of dry weight were recorded in 80 random quadrat (50x50cm2) samples. If no differences in rank could bg seen, first and second places, second and third places or first, second and third places were allocated equally to two or three species. The data were tabulated to give the proportion of quadrats in which each species received first, second and third place. According to the Mannetje and Haydock. (1963) these proportions were multiplied by 70.2, 21.1 and 8.7 respectively, and added to give the dry weight percentage of each species. DWRM was tested five times by comparing the results with those obtained by hand separation method. With each test, actual HS values gradually became more closely related to DWRM values indicating a positive and significant (p<0.05) correlation (0.65). Therefore it was found that accurate data obtained with HS could be predicted using the simple DWRM as an alternative to the HS method in determining botanical composition of tropical pastures.