Enhancing Sustainable Crop Production: Biostimulatory Effects of Fish Hydrolysate and Nano-Sized Fish Hydrolysate on Kale and Lettuce Growth, Yield, and Phytochemical Composition

Abstract

As global food demand increases, and environmental issues become more pressing, sustainable agriculture practices are essential for improving crop output while reducing ecological effects. This study investigated the efficacy of fish hydrolysate (FH) and nano-sized fish hydrolysate (nFH) as biostimulants to enhance the growth and development of kale (Brassica oleracea var. sabellica) and lettuce (Lactuca sativa L.). Kale seeds and seedlings were subjected to FH concentrations of 0% (control), 0.25%, 0.5%, 1%, and 2% during germination and seedling growth experiments, while both crops received nFH treatment at sonication durations of 0, 15, 20, 25, and 30 mins, administered via soil drench and foliar application methods. The germination study indicated that 0.25% FH significantly increased kale germination by 15% compared to the control, resulting in an increase in root surface area. Greenhouse findings demonstrated that 2% FH boosted kale fresh weight by 43.35%, along with an increase in leaf count and photosynthetic efficiency compared to the control. In nFH, the 25-min soil drench application optimized biomass in both species, with lettuce exhibiting a 30% greater rosette diameter than the foliar treatment. Soil drench applications consistently outperformed foliar sprays, ensuring sustained nutrient delivery. Analytical techniques, such as scanning electron microscopy, validated that sonication diminished particle sizes, hence improving nutrient availability, while mineral analysis indicated elevated concentrations of key minerals, including potassium (1610 mg/L) and calcium (1410 mg/L) in FH. This study revealed that FH and nFH, especially at optimal concentrations and sonication durations, significantly enhanced plant growth and resistance, providing a sustainable method for utilizing fish waste in agriculture.