Fish waste extract as a sustainable alternative to inorganic fertilizers in salad cucumber, Cucumis sativus cultivation: growth and yield insights

Foliar fertilization is one of the most important methods for applying nutrients to crops. The main objective of this research was to determine the effect of the application of fish waste extract (FWE) on the growth and yield parameters of salad cucumber (Cucumis sativus L). Tilapia (Oreochromis niloticus) fish waste was mixed with brown sugar (1:1 w/w) and fermented for 21 days. Five mL filtrate was then diluted in 1 L of water. The tested treatments were: Fertilizer recommendation of the Department of Agriculture (DOA), Sri Lanka (T1), FWE of 20 % (T2), 30 % (T3), 40 % (T4), and 50 % (T5). The commercial hybrid cucumber variety ‘Multistar RZ F1’ seeds were germinated in germination trays filled with a topsoil and compost mixture (1:1 w/w). Two weeks old seedlings were transplanted in 30 cm x 30 cm polyethylene bags filled with topsoil media. The plants were treated with different concentrations of FWE at weekly intervals from the first week to the twelfth week as a foliar application. Post treatment assessments were taken after twelve weeks. FWE- treated plants reported significant increases in plant height (475.4 ± 2.99 cm) and number of leaves (50.5± 0.28) compared to the control, 239.3 ± 4.18 cm and 33.25 ± 0.25, respectively. Leaf dimensions were significantly larger, with leaf length and width reaching 26.87 ± 0.23 cm and 27 ± 0.2 cm in FWE-treated plants, compared to 13.87 ± 0.42 cm and 13.8 ± 0.42 cm in the control. Fresh fruit weight rose significantly to 640 ± 47.8 g in treated plants compared to 150 ± 21.2 g in the control, while fresh shoot weight increased (912.5 ± 23.6 g vs. 300 ± 20.4 g). FWE-treated plants produced a significantly higher number of fruits per plant (15 ± 0.7) compared to the control (2.75 ± 0.4). These results highlight the effectiveness of fish waste extract as a sustainable solution for enhancing cucumber growth and yield.