GROUNDNUT GROWTH AND DEVELOPMENT IN CONTRASTING ENVIRONMENTS-1 - GROWTH AND PLANT-DENSITY RESPONSES

Data from studies of growth and development, and response to plant den sity in common groundnut (Arachis hypogaea) cultivars were examined fr om published studies. Data were available from the humid tropics of In donesia, the semi-arid tropics of north-west Australia and the humid c oastal and inland elevated areas of north-east Australia. Temperature and irradiance played a major role in determining crop duration, indiv idual plant size and partitioning of dry matter to pods across environ ments, and these plant characteristics provided the major determinants of pod yield and response to plant density. Crop duration was shortes t in humid tropical and subtropical environments, with both high and l ow temperatures apparently delaying crop maturity. A relatively small individual plant size in humid tropical environments was due to a comb ination of low incident irradiance and shore duration, with very high plant densities needed to maximize dry matter production. The progress ive decline in harvest indices in more tropical environments was due t o a decline in pod numbers per plant. Although increased plant density resulted in greater numbers of pod initials in the humid tropics, a h igh proportion of these pods did not contain developed seeds and pod y ield at high densities remained relatively low at less than or equal t o 2.5 t ha(-1).