THE INFLUENCE OF SOLID URBAN WASTE COMPOST AND NITROGEN-MINERAL FERTILIZER ON GROWTH AND PRODUCTIVITY IN POTATOES

The influence of solid urban waste (SUW) compost and nitrogen (N)-mine ral fertilizer on the growth and productivity in semi-early harvest po tatoes (Solanum tuberosum L., var. 'Edzina') was studied over a period of three years. Nine treatments derived from a factorial combination of 3 levels of SUW compost (0, 18, 36 T.ha(-1)) and 3 levels of N-mine ral fertilizer (0, 125, 250 Kg N ha(-1)) were carried out on a sandy, moderately fertile plot. The applications of SUW compost and N-mineral fertilizer showed a stimulation in plant development with respect to the non-treated controls. The mineral fertilizer treatment gave marked ly higher results. Plant response to the combined mineral fertilizer-c ompost treatments demonstrated a tendency towards saturation within ea ch level of application. Potato productivity results indicated that th is crop reacts strongly and positively to an application of N-mineral fertilizer, but only slightly to the treatment levels of compost consi dered in the study. As a consequence of the application of SUW compost , the application-response graphs reveal a reduction in the optimal le vels of N-mineral fertilizer application and an increase in the effica cy of the mineral fertilizer.