3.1. Fertilizer × planting date interaction
The fertilizer rate × planting date interaction affected antioxidant
activities in fruit (Fig. 1). Antioxidant activities increased as
fertilizer rate increased to 135 kg ha−1 of NPK as observed from the
curve. A quadratic model produced fits for all planting dates. The
same responses were observed for the fertilizer rate × planting date
interaction on phenolic antioxidant concentrations (Figs. 2 and 3)