Growth Rate of Eggplant Under Nitrogen and Phosphate Fertilization and Irrigated With Wastewater

Wastewater use has become an alternative for agriculture in arid and semi-arid areas due to water scarcity besides providing nutrient for plants. This work aimed to evaluate the effects of the interaction of nitrogen and phosphorus doses associated with wastewater on the growth rate of eggplants in the stages of vegetative growth and beginning of fruiting in the semi-arid of Brazil. The wastewater was previously treated using sand filter with intermittent flow. The experiment consisted of a randomized block design in a 4 × 4 + 1 factorial scheme, with four replications. The factors consisted of four nitrogen doses (N1 = 0.22, N2 = 0.39, N3 = 0.56 and N4 = 0.72 g dm-3 of soil), four doses of phosphorus (P1 = 0, P2 = 1.68, P3 = 2.40 and P4 = 3.12 g dm-3 of soil), both using wastewater, and a control treatment (100% nitrogen and phosphorus using drinking water). The interaction of wastewater with nitrogen and phosphorus doses influenced all growth rates at the vegetative stage, except for the relative number of leaves. We found interaction for the relative rates of stem diameter and number and area of leaves at the beginning of the fruiting stage. Nitrogen and phosphorus doses associated with wastewater were excessive even below the recommendation for eggplant cultivation, however, in the absence of wastewater the plants reduce the growth rates of stem diameter and leaf area in the initial period of the fruiting.