Response of greenhouse tomato crop to NPK fertilization and quality of irrigation water

This work studies the effect of different nitrogen-phosphorous-potassium (NPK) dosages applied by fertigation and two types of irrigation water on tomato production under greenhouse conditions. The experiment was conducted on a greenhouse 'Pitenza' tomato crop, on a sand-mulched sandy loam soil and trickle irrigation. Two factors were considered: fertigation dosage and quality of irrigation water. Three NPK dosages, equivalent to 50, 100 and 200% of the crop uptake under the local conditions, were established, being the total N, P, K concentration of treatment 100% 40.1, 7.6 and 54.1 g m(-2) respectively. Two sources of water of different E.C. were also adopted (C.E.: 0.6 and 2.2 dS m(-1)). The tomato crop showed a positive response to an increase of the nutrient solution NPK concentration, which raised the NPK extraction, yield and number of fruits per truss. An increase of the nutrient concentration from 100 to 200% produced a slight increase of yield (less than 10%), but lowered the nutrient uptake efficiency (27% for N, 44% for P and 34% for K). Irrigation water E.C. of 2.2 dS m(-1) (until 3.7 dS m(-1) of the nutrient solution) did not limit the marketable yield of tomato.