The stem growth, nutrition, and fruit yield of eggplant grown with different doses of cattle manure (CM) and magnesium thermophosphate (MT) were studied, according to the Central Composite Matrix of Box (8.3-518; 8.3-3,018; 48.3-518; 48.3-3,018; 0.0-1,768; 56.6-1,768; 28.3-0.0; 28.3-3,536; 28.3-1,768). Potassium sulfate (KS) was also used (24 g plant-1), as well as a cow urine (COU) solution (10 L 100 L-1 H2O, 500 mL plant-1), applied five times in topdressing. Two additional treatments were used: MT without COU and triple superphosphate + urea (TS plus Ur), both with nutrient levels (CM, P2O5, and KS) corresponding to the combination 28.3-1,768. The experimental design was blocks at random, with three replications. CM doses improved plant height (PH) (29.1 t ha-1 of CM; 69.84 cm) and stem diameter (37.8 t ha-1; 19.8 mm), fitting into a quadratic model. However, due to the positive interaction between CM and MT, PH increased up to 86.87 cm when the same CM dose was combined with 3,536 kg ha-1 of MT. CM doses had also a quadratic effect over number of fruits, fruit production per plant, average fruit weight (AFW), and yield, with respective maximum values corresponding to 53.4 t ha-1 (13 fruit), 55.8 t ha-1 (2,822 g plant-1), 47.8 t ha-1 (210 g fruit-1), and 48.8 t ha-1 (34.3 t ha-1), without significant effects of MT. N and P foliar contents did not change with treatments. CM doses increased K, Ca, and S, and decreased Mg foliar contents. But, concerning Ca, was observed negative interaction of MT. COU showed no effect over the characteristics analyzed. The effect of TS + Ur was larger than that of MT + COU on PH and production indexes, except for AFW, but did not differ from them as to macronutrient foliar contents.
Solanum melongena; organic fertilization; alternative fertilization management; unconventional fertilization
