Addressing the challenge of variability in seaweed extracts
Seaweed biostimulants are gaining significant attention in agriculture due to their ability to enhance crop quality, yield, and stress tolerance by activating physiological and biochemical processes in plants.1 However, achieving consistent and reproducible performance with seaweed biostimulants in crop production can prove challenging.2 This challenge arises from differences between seaweed species, variations in the seaweeds themselves, as well as the extraction methods used to extract their active ingredients and manufacture into the final product.3
At Afrikelp, the brown seaweed, Ecklonia maxima is sustainably harvested off the west coast of South Africa and processed via the Cold Micronisation Process (CMP). This gentle extraction technique is crucial for preserving and enhancing vital bioactive compounds, ensuring their effectiveness in on field performance of the biostimulant.
Furthermore, to address the challenge of variability in seaweed extracts, we have implemented standardisation as a crucial step in product formulation. This process establishes uniformity and quality control measures of bioactive materials, such as phytohormones, simple and complex carbohydrates, and essential organic matter found in seaweed biostimulants. Standardisation efforts aim to ensure the reliability and effectiveness of Afrikelp products across different processing and harvesting contexts and conditions, thereby supporting their widespread adoption, and enhancing their impact on agricultural productivity and sustainability.
Globally, citrus production is a major agricultural sector, with the Food and Agriculture Organisation (FAO) reporting over 146 million metric tons produced in 2021. South Africa is a major player in this industry, contributing around 3.4 million metric tons annually, with exports reaching approximately 2.2 million metric tons (65% of total production), making it one of the top citrus exporters globally.4 Seaweed-based biostimulants have been used in citrus farming due to their ability to enhance growth, yield, and resilience against stress.5,6 These biostimulants contribute to higher production efficiency and better-quality fruit.7 Recent studies highlight their role in sustainable agriculture, underscoring their growing importance in the citrus industry.3
In independent trials conducted over two seasons by researchers at UC Chile University in Linderos, Chile on Oranges (var. Fukumoto) (Figure 1) and UC Riverside in California, USA on Mandarin (var.Tango) (Figure 2), consistent increases in marketable yield were demonstrated with Afrikelp LG1® applications compared to the untreated control.
The results from the trials conducted on Oranges (var. Fukumoto) in Chile indicated an average increase of 25% in marketable yield over two seasons. Considering the average exchange rates and fruit prices in Chile at the time, this increase translates to an estimated average of R31 209 of additional marketable yield or R76 760 of potentially exportable yield per hectare over the two seasons.
Similar results were observed in the trial conducted on Mandarin (var. Tango) in California, USA. The average increase of 29% in marketable yield over the two seasons, based on exchange rates and US fruit pricing, translates to an estimated average of R125 470 of additional marketable product or R278 919 of potentially exportable product per hectare over the two seasons. In both cases substantially more than the input cost of the Afrikelp LG1®.
Biostimulants are also recognised for their significant impact on improving the quality of citrus fruits by enhancing nutrient uptake and bolstering the plants natural defence mechanisms.8 These substances improve various aspects of fruit quality including size, colour, flavour, and nutritional content.9
To determine the effect of seaweed biostimulants on citrus quality, independent trials conducted by external researchers Agrivance in Stellenbosch, South Africa, on Lemon varieties Eureka and Lisbon demonstrated the effectiveness of Afrikelp LG1® in increasing fruit firmness. A 7% increase across both varieties was observed (Figure 3). Firmer citrus fruits are less susceptible to physical damage and have thicker peels, which help maintain fruit weight and prolong shelf life, all contributing to higher export quality.10
These results highlight the effectiveness of Afrikelp’s CMP extraction process coupled with rigorous standardisation and quality control measures, to produce a seaweed biostimulant that delivers consistent and significant improvements in yield and quality of citrus across different seasons, locations, and varieties. This enables farmers to make better decisions, increase productivity, and maintain sustainable farming practices, all of which contribute to their success and profitability.
Alec Edwards, Bongo Majeke, Dunesha Naicker and Samkelisiwe Zulu
Afrikelp (Pty) Ltd, 22A Falcon Crescent, Matroosfontein, Cape Town, 7490
References
[1] De Clercq et al. (2023). Effect of Seaweed-Based Biostimulants on Growth and Development of Hydrangea paniculata under Continuous or Periodic Drought Stress. Horticulturae. 9(4):509.
[2] Li et al. (2023). A Meta-Analysis of Biostimulant Yield Effectiveness in Field Trials. Frontiers of Plant Science. 13:836702.
[3] Ali et al. (2021). Biostimulant properties of seaweed extracts in plants: Implications towards sustainable crop production. Plants, 10(3), 531.
[4] Food and Agriculture Organization of the United Nations (FAO). (2022). Major Tropical Fruits – Statistical Compendium 2021. Available at: https://www.fao.org/markets-and-trade/publications/detail/en/c/1438250/ (Accessed: 01 June 2024).
[5] Fornes et al. (2002). Effect of a seaweed extract on the productivity of “De nules” clementine mandarin and Navelina Orange. Botanica Marina, 45(5).
[6] Kenawy et al. (2022). Effect of potassium, microelements and seaweed extract spraying on yield and fruit quality of Balady Mandarin (citrus reticulate blanco). Assiut Journal of Agricultural Sciences.
[7] Khan et al. (2022). Supplemental foliar applied mixture of amino acids and seaweed extract improved vegetative growth, yield and quality of citrus fruit. Scientia Horticulturae, 296, 110903.
[8] Basile et al. (2020). Appraisal of emerging crop management opportunities in fruit trees, grapevines and berry crops facilitated by the application of biostimulants. Scientia Horticulturae, 267, 109330.
[9]Rana et al. (2022). Sustainable production through biostimulants under Fruit Orchards. CABI Agriculture and Bioscience, 3(1).
[10] Fernández et al. (2021). Effects of different comercial coatings on postharvest citrus fruit quality for export. Agrociencia Uruguay, 25(1).
