This research was carried out at Lavras, Minas Gerais State (Brazil) in 1997. The objective was to study nutrient absorption by tomato plants pruned and grown under high planting density over different gypsum, P2O5 rates and different N and P sources. The yield was also analyzed, considering conventional planting systems. The experimental design was of complete randomized blocks with four replications in a factorial scheme 3 x 4 with three rates of P2O5 triple superphosphate (0.2, 0.4, and 0.6 t/ha) and four rates of gypsum (0.3, 0.6, 0.9 and 1.2 t/ha). Four additional treatments were included about planting system and soil fertilization. A linear increase was observed on the commercial tomato yield with the increasing of P2O5 rates whereas linear decreasing was observed with the increasing of gypsum rates. The production up to 149.2 t/ha was obtained with plants pruned and grown under high planting density. The lower production, 91 t/ha (pruned plants) and 63.2 t/ha (not pruned plants), was obtained using ammonium sulfate (N source) and single superphosphate (P source). Leaf P contents, with values around 3.0 a 1.7 g/kg, decreased with the increase of gypsum rates. The lower leaf P content was observed in the additional treatment with ammonium sulfate and single superphosphate. The mean value of magnesium contents was 4.7 g/kg without statistically significant differences considering gypsum and P2O5 treatments. Otherwise values of magnesium contents around 3.0 g/kg were found under additional treatments, statistically different when compared to the treatments above mentioned. The observed Cu values of 79.4 mg/kg in another additional treatment using urea as N source, and triple superphosphate as P source was statistically different with values of 120.6 g/kg, observed in the first additional treatment. Leaf Cu contents also increased with the increase of gypsum rates. Its was concluded that high levels of fertilizers with sulfur can inhibit P uptake mainly in high planting density. Reduction of number of fruits per plant by pruning associated with high planting density can increase the yield.
Lycopersicon esculentum Mill; phosphorus and gypsum fertilizers; production system
