Abstract

Sustainable agriculture focuses on reducing the excessive use of inorganic fertilizers while sustaining crop productivity and improving profitability. In Senegal, onion is an important cash crop and widely grown in the Senegal River Valley and the Niayes agroecological zones. However, its production depends on the intensive use of chemical fertilizers, which has negative effects on soil health and environment. This study assessed the effects of the single or combined application of OCASE® biostimulant, made from nettle (Urtica dioica) and dandelion (Taraxacum officinale), with decreased rates of NPK on onion growth, yield, shelf-life and economic profitability under field conditions. The experiment was laid out in a randomized complete block design with four replications and six fertilization treatments: control, recommended rate of NPK fertilizer (10-10-20 – 300 kg/ha), OCASE® biostimulant (10 L/ha) and its combination with 75%, 50% and 25% of the recommended of NPK rate. Results showed that OCASE® + 25% NPK significantly enhanced bulb weight (377.5 g), plant height (58.15 cm), and overall yield (67.89 t/ha), which were greater than the recommended rate of NPK. This treatment combination also improved postharvest storability with a decreased water loss and disease incidence compared with the NPK fertilizer alone. The highest economic gain (USD26301.28), profit (USD25891.03), and value: cost ratio (64.11) was also achieved with OCASE® biostimulant + 25% NPK, demonstrating its profitability. In crux, application of OCASE® biostimulant with 25% of the recommended dose of NPK could be a sustainable alternative to synthetic fertilizers for improving onion productivity, postharvest losses and environmental sustainability in Senegal.