EVALUATION OF THE GROUNDNUT MODEL PNUTGRO FOR CROP RESPONSE TO PLANT-POPULATION AND ROW SPACING

Field experiments were conducted during the 1987, 1991 and 1992 rainy seasons at Patancheru (latitude 17-degrees32'N; longitude 78-degrees16 'E; elevation 545 m), Andhra Pradesh, India, to collect data to test a nd validate the hedgerow version of the groundnut model PNUTGRO for pr edicting phenological development, light interception, canopy growth, dry matter production, pod and seed yields of groundnut (Arachis hypog aea L.) as influenced by row spacing and plant population. The model w as calibrated using the crop growth and phenology data of groundnut (c v. Robut 33-1) obtained from the 1987 and 1991 rainy season experiment s. In these experiments groundnut was grown at plant populations rangi ng from 5 to 45 plants/m2 with and without irrigation. Changes were ma de in the cultivar-specific coefficients related to the light penetrat ion into the crop canopy and dry matter production. The model was vali dated against independent data obtained from a 1992 rainy season exper iment. In 1992, groundnut was grown at plant populations ranging from 10 to 40 plants/m2 and at row spacings of 20, 30 and 60 cm. The model predicted the occurrence of vegetative and reproductive stages, canopy development, total dry matter production and its partitioning to pods and seed accurately. Maximum leaf area index observed during the seas on was significantly correlated with simulated values (r2 = 0.95). In spite of some incidence of diseases and pests, the correlation between simulated and observed pod yield was significant (r2 = 0.61). It is c oncluded from this study that the hedgerow version of the groundnut mo del PNUTGRO can be used to quantify groundnut growth and yields as inf luenced by plant population and row spacing.