Effect of Nitrogen:Potassium Fertilization Ratios and Biostimulant Application on Broccoli Plants

Broccoli ( Brassica oleracea ) is an annual herbaceous plant that is widely consumed due to its high nutraceutical potential. To improve crop development, it is necessary to determine an adequate supply of nutrients, both in terms of quantity and balance. Additionally, the use of phytohormone-based biostimulants is proving promising for increasing plant growth. Here, we aimed to determine the ideal ratio of nitrogen (N) to potassium (K) and the effect of biostimulants on broccoli plants. Broccoli plants were cultivated by fertilization with four N:K ratios (1:1, 1:2, 1:3, and 3:1) and five doses of a plant phytohormone-based biostimulant (0, 0.5, 1.0, 1.5, and 2 mL L −1 ). At 90 days of culture, plant height; stem diameter; leaf number; leaf area; fresh and dry mass of stems, leaves, and inflorescences; organ mass fraction; chlorophyll content; and gas exchange were assessed. The experiment was completely randomized in a factorial scheme of 4 × 5 (N:K × doses of biostimulant) with eight replications, each composed of a pot with one plant. Data were subjected to analysis of variance and means were compared using Tukey’s test ( P ≤ 0.05). Fertilization with 1:1, 1:2, and 3:1 N:K resulted in higher inflorescence fresh masses, indicating that these ratios are appropriate for broccoli production, regardless of the biostimulant dose. The 1:2 N:K ratio was optimal for broccoli inflorescence production and plant architecture, independently of the biostimulant. These findings support fertilization programs aimed at increasing broccoli production.