EFFECTS OF NITROGEN, PHOSPHORUS AND POTASSIUM FERTILIZATION ON THE GROWTH AND YIELD OF RADISH ON A VERTISOL

In this agronomic study, the effects of varying levels of NPK fertilizers on the growth and yield of radish [Raphanus sativus (/.)] on Tarouba clay (fine montmorillonite, Aquentic Chromudert), were investigated. Tarouba clays are typical sugar cane Vertisols in South Trinidad allocated for '2-acre' small holder farms as part of the Caroni 1975 diversification programme. Nitrogen fertilization at the rates of 60, 120 and 180 kg/ha in the presence of varying rates of phosphorus (30, 60 and 90 kg/ha) and potassium (180 and 220 kg/ha) fertilizers were applied at planting under field conditions. The application of 120 kg N, 60 kg Ρ and 180 kg K/ha had a significant effect (P = 0.05) on all agronomic characteristics including leaf number, leaf length, root length, root girth, root weight and yield per hectare. Increased levels of nitrogen to 180 kg/ha had a significant impact on plant characteristics, with lower root length, root girth and yield per hectare, although the vegetative characteristics were also significantly lower. The response to levels of phosphorus and potassium were less pronounced, with significant effect at 60 kg P/ha and no effect of potassium fertilizer. The yield response indicates that radish can be introduced as a niche crop on Southern Vertisols