HYDROPONIC CULTURE OF TOMATO WITH COCONUT COIR DUST AS SUBSTRATE, AND ITS RESPONSE TO AMMONIUM AND POTASSIUM

Abstract

Plants of tomato (Lycopersicon esculentum Mill.) cv. Celebrity were grown in a hydroponic system type sub-irrigation, under greenhouse conditions, using an organic material derived from milled coconut (Cocos nucifera L.) coir (washed and decanted) as substrate. Three ratios of ammonium: 8.3, 16.6 and 25.0 % of total nitrogen; three ratios of potassium: 10, 20 and 30 % with respect to total cations; and three levels of dust calcium carbonate mixed with the substrate (0, 3 and 6 g kg-1), were evaluated. The nutritive solutions were preparated according to the Steiner solution principles, having an average osmotic potential of 0.070 MPa during the vegetative stage and of 0.083 MPa during the fructification stage. The highest fruit and dry matter yields were obtained when the nutritive solution contained 16.6 % of ammonium, 30 or 20 % of potassium, and 3 or 6 g kg-1 of dust calcium carbonate incorporated to the substrate. The coconut coir dust, deprived of fine particles and washed with water, showed a good potential as substrate, since it surpassed the untreated coconut coir dust, and proved a similar or better behavior than the Canadian peat moss.