Agriculture Business Week

A low-cost and effective organic fertilizer from seaweeds has been developed by researchers of the Southern Philippines Agribusiness and Marine School of Technology .

Fertilizers are major inputs in agriculture and aquaculture. The rising prices of petroleum-based chemical fertilizers have increased production costs of farms in the country and reduced farmers’ incomes. The use of organic fertilizers in combination with inorganic fertilizers is now being promoted by the government to improve farm profitability and protect the environment.

A low-cost and effective organic fertilizer from seaweeds has been developed by researchers of the Southern Philippines Agribusiness and Marine School of Technology (SPAMAST) in Davao del Sur led Gracilla Caballero. The technology was based on the observation that ornamental plant growers use the exudate or drippings of seaweeds for fertilizing orchids. To determine whether there was any scientific basis for such practice, the SPAMAST scientists conducted studies.

It is common practice for seaweed farmers to dry the freshly harvested marine algae in elevated platforms or nets on the ground under the sun before being sold to processors. The plants contain more than 80% water and have to be dried to a moisture content of about 40% to fetch a good price.

The researchers found that the drippings from the cultured red seaweeds (Kappaphcus and Eucheuma) that usually go to waste constitute about 75% of their fresh weight after 3 days of drying. This means that for every loo kilos of fresh seaweeds dried, 75 liters of drippings can be collected by hanging the plants on lines like laundry and then placing a plastic sheet under them for the drippings to funnel into a container below.

An analysis of the seaweed exudate showed that it contained 0.14% nitrogen,1.14% phosphorus, 3.25% potassium, 0.041% magnesium, 0.018% calcium, and had a pH of 5.2. Seawater, on the other hand, only has 15.5 parts per million (ppm) of nitrogen, 0.088 ppm of phosphorus, 392 ppm of potassium, 411 ppm of calcium and 1,290 ppm of magnesium with a pH of 8. The analysis showed that the exudate is a good source of phosphorus and potassium for growing plants.

Initial tests on the use of the seaweed liquid fertilizer for growing vegetables and rice gave very promising results. In mixing 15 milliliters of the concentrate for every liter of water and applying three liters of the mixture per hectare at 15 days after planting (DAP), 30 DAP and 45 DAP, the yield of rice was comparable if not better than that of the plant fertilized with inorganic fertilizers. An added bonus was that there was no need for the application of insecticides for growing the seaweed exudate-fertilized plant.

The simple but innovative technology merits further study and wider application. It could provide another income-generating opportunity for the more than 100,000 coastal families dependent on seaweed farming particularly in Mindanao. It can also make land farming more efficient and environmentally-friendly.

The Philippines is one of the world’s largest producers of fainted seaweeds. There are an estimated 150,000 hectares of coastal waters in the country that are used for the industry. In 2008, we produced almost 2 million metric tons of fresh seaweeds.

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