NONDESTRUCTIVE MEASUREMENTS OF BIOMASS IN MILLET, COWPEA, GROUNDNUT, WEEDS AND GRASS SWARDS USING REFLECTANCE, AND THEIR APPLICATION FOR GROWTH ANALYSIS

A simple hand-held reflectometer was used to estimate the shoot dry ma tter of pearl millet (Pennisetum glaucum), groundnut (Arachis hypogaea ), cowpea (Vigna unguiculata), weeds and grass swards non-destructivel y. While the instrument was able to predict shoot dry matter well for single, standing millet and cowpea plants and proved useful for a grow th analysis of millet, its reliability was unsatisfactory for groundnu t. For millet, the slope of two separate regressions between the diffe rence of reflectance ratios and shoot dry matter, taken 10 days apart, was almost identical. This suggests a possible simplification in futu re crop growth models. The usefulness of the instrument for estimating dry matter in natural species mixtures such as weeds and grasses depe nded on the homogeneity of the mixture and the uniformity of their phy siological state.