Evaluating the Effects of Three Seaweed Extracts on the Growth and Yield of Three Crops

Since arable-land availability is limited worldwide, research on other sustainable practices to improve crop productivity is needed. Seaweed extracts are known for their crop growth- and yield-promoting properties and as a sustainable solution. The application of three seaweed extract brands (Acadian, Afrikelp, and Kelpak) was tested on three crops under field (common bean) and screen-house (bell pepper and tomato) conditions for two consecutive seasons/crops. The study was conducted as an RCBD with five blocks using a drip irrigation system. The three seaweed extracts + water-only (control) treatments were randomly distributed in each block. The extracts were applied to the foliage five times in each growing season at a 1:75 extract/water dilution rate and all crops received N-P-K fertilizer based on the recommended rates for each crop. Analysis of variance and Tukey’s mean separation were conducted on the collected data. All three extracts significantly outperformed the control across all crops and seasons. For bush bean, seaweed treatments significantly increased SPAD, yield, and protein content, with the treatment order Afrikelp > Acadian ≥ Kelpak > Control. For tomato, significant improvements were observed in SPAD, yield, and fruit weight, with yield increases driven primarily by fruit count and average; the treatment order was Afrikelp > Kelpak ≥ Acadian > Control. For bell pepper, SPAD, yield, and BRIX were significantly increased, with the treatment order Afrikelp > Kelpak > Acadian > Control. Overall, Afrikelp consistently produced the highest responses across all crops, achieving up to 48.8, 60.3, and 58.6% yield increases for bush bean, tomato, and bell pepper, respectively. The results showed that seaweed extract can serve as a sustainable amendment for crop improvement.