Abstract

Sustainable agriculture is essential to addressing global food security and environmental challenges. One promising approach involves using natural, renewable resources, such as seaweeds, to improve soil fertility and crop growth. A genus of brown seaweed called Sargassum has drawn interest as a biofertilizer because of its high concentrations of organic chemicals, minerals, and hormones that promote plant growth. The impact of Sargassum seaweeds as biofertilizers on crop yields, nutrient availability, and soil health is examined in this study. This study shows how Sargassum-based biofertilizers can improve soil structure, boost nutrient uptake, and lessen reliance on traditional fertilizers by investigating the biochemical characteristics of Sargassum and its effects on plant growth. Despite its potential, sargassum adoption as a biofertilizer comes with difficulties, such as logistics of collecting and processing, public opinion, and legal restrictions. However, certain initiatives and case studies have demonstrated effective implementations, with farmers providing firsthand accounts of enhanced soil health and higher yields. These results establish sargassum as a sustainable and feasible agricultural input that benefits coastal communities affected by sargassum blooms economically and environmentally. To promote broader adoption and establish sargassum as a scalable solution for sustainable agriculture, the study emphasizes the significance of ongoing research and innovation to optimize sargassum collection, processing, and application methods. Adopting sargassum supports resilient food systems, environmental stewardship, and sustainable development goals. It also aligns with sustainable agricultural aims. This study suggests more investigation into the wider uses of sargassum to support sustainable food systems around the world.

Keywords: Sargassum Seaweed; Biofertilizer; Sustainable Agriculture; Food Security; Environmental

Introduction

Sustainable agriculture is becoming increasingly important as global populations rise and environmental degradation accelerates. Current farming techniques frequently rely significantly on chemical fertilizers, which contribute to soil deterioration, pollution, and biodiversity loss. In response, there's growing interest in sustainable agricultural practices. Alternatives like organic farming, integrated nutrient management, and biofertilizers aim to maintain soil health, protect water resources, and preserve biodiversity. These approaches offer a more sustainable future for agriculture, addressing the challenges posed by conventional fertilizer use while meeting productivity needs. Among these, biofertilizers have gained attention for their ability to maintain soil fertility while promoting environmental sustainability.

Sargassum seaweed, a widely available marine resource, is a potential biofertilizer due to its rich nutrient profile and ability to improve soil health. Its utilization offers a sustainable alternative to conventional fertilizers, with benefits extending beyond agriculture to environmental and economic spheres. This brown macroalgae, which has been inundating Caribbean beaches in massive quantities since 2011, presents both a problem and an opportunity for coastal communities.

As concerns over the environmental impact of synthetic fertilizers grow, researchers and entrepreneurs are exploring innovative ways to utilize Sargassum as an eco-friendly alternative. This seaweed is rich in essential nutrients and minerals, including iron, magnesium, potassium, and calcium, which can significantly improve soil quality and plant growth. Moreover, Sargassum contains plant growth hormones and beneficial microorganisms that can stimulate plant development and enhance nutrient uptake efficiency [1].

The potential benefits of Sargassum as a biofertilizer extend beyond its nutritional content. Studies have shown that it can reduce the need for nitrogen-based fertilizers by up to 30%, aligning with sustainable agriculture practices and potentially decreasing the environmental impact of farming. Additionally, the use of Sargassum in agriculture could provide a solution to the economic and ecological challenges posed by its excessive coastal accumulation.

However, the utilization of Sargassum as a biofertilizer is not without challenges. Concerns about heavy metal contamination, particularly arsenic, necessitate proper processing and treatment before application [2]. Furthermore, the seasonal and unpredictable nature of Sargassum blooms presents logistical hurdles for establishing a consistent supply chain [3].

Despite these challenges, the growing interest in Sargassum-based agricultural products demonstrates the potential for innovative, sustainable solutions in farming practices. As research continues and processing techniques improve, Sargassum biofertilizers could play a significant role in promoting more environmentally friendly agriculture while addressing the issues associated with its coastal accumulation. This review explores the potential of Sargassum seaweed as a biofertilizer for sustainable farming.

Sargassum Seaweed: Composition and Nutritional Properties

Sargassum is a widely abundant brown macroalgae found along coastlines worldwide, known for its rich nutrient profile essential for plant growth [4]. It serves as an excellent source of organic nitrogen, with protein content ranging from 11.20% to 13.46% of its dry weight. Additionally, Sargassum is rich in phosphorus (P) and potassium (K), making up 17.56% to 35.18% of its ash content, along with calcium (Ca) and magnesium (Mg) [5].

Sargassum contains a diverse array of macro and micronutrients essential for plant growth. Its protein content typically ranges from 11-13% of dry weight, providing a rich source of organic nitrogen1. The ash content is particularly high in phosphorus and potassium, ranging from 17- 35%, along with significant amounts of calcium and magnesium [4]. The nitrogen content in Sargassum varies depending on environmental conditions and species. Studies have shown that tissue nitrogen levels in Sargassum can range from 0.5% to over 3% of dry weight [1]. Potassium is one of the most abundant minerals in Sargassum, with levels reaching up to 4,170 mg per 100g of dry weight of Sargassum naozhouense [5]. In Sargassum polycystum, potassium levels of 1,711 mg per 100g of dry weight have been observed [6].

Apart from its nutrient content, Sargassum contains organic compounds like alginates, polysaccharides, and plant growth regulators such as auxins, cytokinins, and gibberellins. These bioactive compounds promote root elongation, enhance nutrient absorption, and improve plants' resilience to environmental stresses [7]. These organic compounds improve soil structure by enhancing moisture retention and promoting the formation of stable soil aggregates [8]. This, in turn, leads to better aeration and nutrient availability, creating an optimal environment for root growth [1].

Nutritionally, Sargassum is notable for its high carbohydrate content (around 47-48% of its dry weight), moderate protein levels (11-12%), and low-fat content (1-2%). Its ash content can be as high as 35%, providing minerals and micronutrients like calcium, magnesium, iron, zinc, and copper [5]. Sargassum is also rich in dietary fiber, mainly from water-soluble polysaccharides such as alginates and fucoidans [9]. Additionally, it provides essential amino acids like leucine and valine, which constitute 36-47% of its protein content, with leucine at 6.52 g/100 g protein and valine at 4.64 g/100 g protein. The seaweed also offers vitamins such as vitamin C, vitamin A, and several B vitamins, along with important fatty acids like C14:0, C16:0, C18:1, and C20:4 [5].

Beyond its nutritional components, Sargassum contains a variety of bioactive compounds, including polyphenols, terpenoids, sterols, and sulfated polysaccharides like fucoidans [9,10]. These compounds help mitigate damage caused by reactive oxygen species (ROS), enhancing the plant's resilience to abiotic stress. They are also known for their antioxidant, anti-inflammatory, and antibacterial properties, which further contribute to plant health [2].

However, it is essential to consider that the nutritional profile of Sargassum can vary significantly between different species and environmental conditions. Additionally, by providing essential nutrients, improving soil fertility, and promoting stronger roots and resilience to stress, Sargassum contributes to improved plant health, accelerated growth, and greater overall productivity.

Role of Sargassum as a Biofertilizer

Sargassum indeed provides a range of essential nutrients that support plant growth and development. As it decomposes, it releases these nutrients gradually, offering several benefits to plants and soil health. Sargassum provides a slow release of essential nutrients, including organic nitrogen, phosphorus, potassium, calcium, and magnesium. As it decomposes, these nutrients are gradually made available to plants, ensuring a steady supply over time, which prevents nutrient leaching and supports sustained growth [11]. The high organic nitrogen content promotes protein synthesis and overall plant growth, while phosphorus and potassium enhance root development, flowering, and stress tolerance. The organic compounds in Sargassum, such as polysaccharides and alginates, serve as food for beneficial soil microorganisms. This stimulates microbial growth and diversity, which in turn boosts nutrient cycling, organic matter breakdown, and soil fertility. Increased microbial activity also helps suppress soil-borne pathogens, protecting plants from diseases [12]. Polysaccharides and alginates in Sargassum improve soil moisture retention and contribute to the formation of stable soil aggregates, enhancing soil structure. This leads to better aeration, water infiltration, and root penetration, allowing plants to access nutrients and water more efficiently. The enhanced soil structure helps prevent erosion and increases the cation exchange capacity, improving the soil’s ability to hold and exchange essential nutrients [13].

Environmental and Socio-Economic Benefits of Using Sargassum as a Biofertilizer

Sargassum seaweed, often regarded as an environmental nuisance due to its excessive accumulation along coastlines, holds immense potential as a sustainable biofertilizer. This review explores the environmental and socio-economic benefits of repurposing sargassum, highlighting its role in reducing synthetic fertilizer dependency, improving soil health, mitigating environmental degradation, and fostering economic opportunities for coastal communities. Challenges such as heavy metal contamination and salinity are also discussed, along with strategies for mitigation. The findings underscore the transformative potential of sargassum as an environmentally friendly and economically viable agricultural input. Sargassum inundations present significant threats to marine ecosystems and coastal aesthetics. Utilizing sargassum as a biofertilizer offers an environmentally sustainable approach for managing this biomass, mitigating the accumulation of decomposing seaweed that contributes to eutrophication and biodiversity loss [14]. Sargassum exhibits high concentrations of essential nutrients, including nitrogen (N), phosphorus (P), and potassium (K), rendering it a viable organic alternative to synthetic fertilizers. Its utilization mitigates the environmental impacts associated with chemical fertilizers, such as soil degradation and waterway contamination through nutrient runoff [1]. Sargassum's organic matter contributes to the enhancement of soil structure, water retention capacity, and microbial proliferation. Moreover, the bioactive constituents present in sargassum exhibit the potential to promote root development and augment crop resistance to abiotic stress factors, including drought and saline conditions [13]. Through the enhancement of plant growth and contribution to soil organic carbon, sargassum biofertilizer indirectly facilitates carbon sequestration, thereby aiding in the mitigation of climate change impacts [15]. Secondary metabolites in Sargassum, including polyphenols and flavonoids, exhibit antimicrobial and insecticidal properties. These compounds have the potential to reduce dependence on synthetic pesticides, thereby contributing to biodiversity conservation [9].

There are several socio-economic benefits of Sargassum reported in various research. The utilization of Sargassum for alternative purposes creates new avenues for economic growth. Economically challenged coastal regions can benefit from engaging in the harvesting, processing, and dissemination of Sargassum, thus generating employment opportunities and stimulating local financial development [17]. Agricultural producers, particularly in resource- constrained regions, derive benefit from cost-effective biofertilizers produced from sargassum. These alternative fertilizers are frequently more economically viable than synthetic counterparts, thereby enhancing accessibility to agricultural inputs and mitigating cultivation expenses [18]. Research indicates that sargassum biofertilizers enhance soil fertility and plant productivity. Increased yields contribute to improved food security and elevated income for smallholder farmers, particularly in developing regions [19]. Sargassum proliferation adversely affects tourism-dependent economies through the degradation of coastal aesthetics. The removal and utilization of sargassum contribute to the restoration of coastal environments, thereby indirectly benefiting the tourism sector [20].

Case Studies and Practical Applications

A  60-day  pot  trial  conducted  in  Long  Island,  Bahamas,  evaluated  the  efficacy of Sargassum species as a biofertilizer for cherry tomato cultivation. Various concentrations (1%, 5%, and 10%) of Sargassum were applied to the soil, yielding several significant outcomes. The application notably increased nutrient content, particularly nitrate nitrogen and phosphorus, while also enhancing soil organic matter and salinity levels. However, despite these improvements in soil quality, the study observed negative effects on plant growth parameters compared to the control group. The researchers concluded that caution is necessary when using Sargassum as a biofertilizer in The Bahamas, primarily due to the region's alkaline soil pH, which may limit nutrient bioavailability and hinder plant development.

In the Caribbean, Red Diamond has developed a soil additive product called Supreme Sea using Sargassum seaweed. The Sargassum is carefully collected by hand and processed to create a nutrient-rich additive containing growth-stimulating plant hormones and beneficial microorganisms extracted from the seaweed. Any leftover material is composted into a humus- rich byproduct, ensuring it remains safe and beneficial for crop use. Field trials conducted in Spain demonstrated significant yield increases in crops such as tomatoes and cucumbers. Currently, testing is underway in Cameroon and other African countries. The product aims to enhance global food security and soil health while addressing the pressing issue of Sargassum inundation in the Caribbean.

Sarga Agriscience has developed SargaExtra, a biostimulant derived from Sargassum seaweed, designed to enhance nutrient uptake efficiency in plants. Field trials have shown yield increases of up to 10%, particularly in crops such as barley, corn, and soy. Additionally, SargaExtra can reduce the reliance on synthetic fertilizers, contributing to more sustainable agricultural practices. The product not only helps address the environmental challenges of Sargassum accumulation but also mitigates nutrient pollution. These case studies underscore the promising potential of Sargassum as a biofertilizer, while emphasizing the importance of proper processing and consideration of local soil conditions to achieve optimal results.

Challenges and Limitations

The utilization of sargassum as a biofertilizer presents several challenges and limitations that necessitate addressing for its sustainable adoption. A significant concern is the accumulation of heavy metals such as arsenic and cadmium, which may pose risks to soil health, crops, and human safety if not adequately treated. Furthermore, the high salinity of sargassum can potentially degrade soil quality and adversely affect crops, particularly in regions already impacted by saline conditions. The variability in nutrient composition across different sargassum species and locations further complicates its application, potentially leading to inconsistent results. Moreover, ecological concerns arise from overharvesting, which may disrupt marine ecosystems and nutrient cycles. Processing and logistical challenges, such as the high-water content of raw sargassum and the requirement for extensive infrastructure, also contribute to the complexity. Additionally, limited farmer awareness and the absence of clear policies and regulations for sargassum collection and use impede its large-scale adoption. Addressing these issues necessitates innovative pre- treatment technologies, sustainable harvesting practices, and policy support to ensure that sargassum can be effectively and safely utilized as a biofertilizer.

Future Perspectives and Research Gaps

Future perspectives on utilizing Sargassum as a biofertilizer necessitate addressing critical research gaps and optimizing strategies for sustainable implementation. A primary objective is the development of cost-effective pre-treatment and processing technologies to mitigate contaminants such as heavy metals and salts, thereby ensuring the biofertilizer's safety for agricultural application. Furthermore, standardizing Sargassum's nutritional profiles through blending and fortification will enhance its consistency and efficacy across diverse crops and soil conditions. While short-term benefits have been demonstrated, the long-term environmental impacts on soil health, microbial diversity, and nutrient cycling require comprehensive investigations. Scaling up production will involve establishing sustainable collection and processing infrastructure, supported by economic feasibility assessments and efficient distribution networks. Moreover, to prevent ecological imbalances, sustainable harvesting practices must be informed by ecological impact studies and regulatory frameworks. Policy interventions, including subsidies and incentives, can also play a crucial role in promoting adoption and fostering research into innovative applications of Sargassum in agriculture. These efforts will ensure that Sargassum biofertilizers are not only environmentally viable but also economically and socially beneficial.

Conclusion

In conclusion, the utilization of sargassum as a biofertilizer presents a promising solution to environmental, agricultural, and socioeconomic challenges, particularly in coastal regions significantly affected by its proliferation. Its nutrient-rich composition, coupled with the potential to reduce dependence on synthetic fertilizers, positions sargassum as a valuable resource for sustainable agriculture. However, challenges such as heavy metal contamination, high salinity, logistical impediments, and ecological trade-offs must be addressed to fully harness its potential. Through innovative pre-treatment technologies, standardized processing methods, sustainable harvesting practices, and supportive policies, these limitations can be mitigated. Future research and collaboration among stakeholders are essential to scale its adoption and ensure that sargassum contributes to a circular economy, environmental restoration, and enhanced agricultural productivity. By addressing these gaps, sargassum can transition from an environmental burden to a cornerstone of sustainable agricultural practices.

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