With the global population expected to hit 10 billion by the year 2050, farmers are required to increase food production by 70% compared to levels from ten years ago. Considering the restricted amount of arable land, the key to addressing this issue is enhancing productivity on current farmland—a task that underscores the critical role of fertilizer.
Most Filipino farmers use chemical fertilizers – also referred to as synthetic or inorganic fertilizers – as they are readily available anytime. These are artificially produced substances that deliver vital nutrients to plants, especially nitrogen, phosphorus, and potassium.
While chemical fertilizers can enhance agricultural output, they come with certain drawbacks. In addition to their high cost, chemical fertilizers may contribute to soil degradation, water pollution, and air pollution as a result of runoff and the emission of greenhouse gases.
Research has indicated that prolonged usage can disturb the natural microbial ecosystem, resulting in a decrease in soil fertility and biodiversity. Excessive application of chemical fertilizers can also lead to nitrate contamination in drinking water, which poses health hazards to both humans and livestock.
In time, environmental advocates and health-conscious individuals are pushing for the use of organic fertilizers or those naturally sourced substances that enhance soil fertility, supply essential nutrients to plants, and support sustainable agricultural practices.
Filipino farmers who grow rice can now grow organic fertilizers along with their crops. This can be made possible by introducing azolla in the field while rice is growing and flooded with water.
In the 11th century, farmers in the Kingdom of Dai Viet cultivated the small water fern within their rice paddies. Although they were unaware of nitrogen – the essential element for plant growth – they recognized that the fern enhanced the growth of their rice.
For centuries, the descendants of those ancient Vietnamese and Chinese farmers utilized the water fern – now referred to as azolla – to enrich their crops and nourish their livestock. Today, the cultivation of azolla is expanding to other rice-growing Asian countries, including the Philippines.
“Any rice plant, modern or traditional, requires one kilogram of nitrogen to produce 15 to 20 kilograms of grain,” said the Laguna-based International Rice Research Institute (IRRI). “Most tropical soils imbibe sufficient nitrogen naturally to grow about one ton or 1.5 tons of rice per year. To augment yields above that, nitrogen must be provided.”
In the 1960s, petroleum-based fertilizers were the most economical practices to add nitrogen to the soil. “But fertilizers are expensive and we are increasingly aware of environmental pollution caused by improper fertilizer use,” says Jethro P. Adang, the director of the Mindanao Baptist Rural Life Center (MBRLC), a non-government organization based in Bansalan, Davao del Sur.
The air around rice is 80 percent nitrogen. Anabaena azollae, a blue-green alga that thrives in the cavities of azolla leaves can fix or draw nitrogen from the air. Azolla floats on the water between rice plants. When it dies and is incorporated into the soil, decomposition releases the nitrogen.
“Farmers who grow azolla are actually growing their own fertilizers,” Adang says, adding that azolla can be used as green manure or biofertilizer.
According to the Azolla Foundation, azolla’s capacity for nitrogen fixation can yield as much as 1100 kg of nitrogen per hectare annually, which is nearly three times the amount produced by conventional legumes.
In addition, azolla is rich in vital macronutrients and micronutrients, including phosphorus, potassium, calcium, magnesium, sulfur, iron, and zinc, all of which contribute to enhanced soil fertility and promote plant growth.
For only three hours, Adang claims, a farmer can grow adequate azolla to increase yields equivalent to that produced by 30-60 kilograms of nitrogen fertilizer per hectare. Residual soil nitrogen is increased.
“Azolla growth does not interfere with normal rice cultivation,” IRRI assures. “In fact, it helps control weeds and improves soil texture.”
A study conducted by the Philippine Rice Institute (PhilRice) demonstrated that rice grown with azolla interspersed between its rows can produce yields of 4-5.3 tons per hectare at a production cost of merely P3.84 per kilogram following continuous incorporation.
Cielo Luz Mondejar-Bello, a member of the research team based at the Negros station, stated that they evaluated azolla as a nutrient source for the rice crop over three seasons, without the application of any other fertilizers.
The initial effects were noted in the second season, when the plants exhibited robust maturation; however, the most significant yield increase was recorded after the third cropping.
“In our demo, we only introduced 0.1kg/ha of azolla fresh biomass during the first two seasons. The fern grew and fully covered the farm during the third season. Based on soil analysis, rice-azolla intercropping areas have increased organic matter and the total nitrogen available in the rice field. Our computation shows that farmers can save P17,500 for two cropping seasons if they use azolla as a biofertilizer for rice,” Mondejar-Bello said.
The application of azolla as a fertilizer was initially advocated in the Philippines during the early 1980s. Research indicates that rice yields in fields utilizing azolla surpassed those in fields without it by over a ton within the same cropping cycle.
One of the key proponents of azolla technology in the nation during that period was Mamerto Fantilanan, who established the “Inilusan” (a local term meaning “the place where people share”) farm in Capiz province.
The initiative was not merely a lucrative enterprise in a rural area where small farms were often equated with poverty. As reported in a publication by the UN Food and Agriculture Organization (FAO), Fantilanan generated an annual income from his 7,000-square-meter farm that was more than double that of neighboring farmers who possessed four times the land area.
Rather than relying on commercial fertilizers, he opted for azolla. “Organic farming involves returning to nature what you extract from it,” Fantilanan was quoted as saying. “It is safe, cost-effective, profitable, and sensible.”
Fantilanan employed azolla to fertilize rice, vegetables, fruit trees, seedlings, and various cash crops. Additionally, he utilized azolla as feed for his ducks, chickens, and pigs. His family also consumed azolla, as his wife prepared delicious azolla burgers and omelettes. “Azolla enhances soil fertility while improving its texture and acidity,” Fantilanan remarked.
His consistent use of azolla reduced the labor required for land preparation. He refrained from plowing the field; instead, he simply pushed the rice stubbles and azolla into the soil with his feet. Subsequently, he leveled the land using a harrow or rake.
Fantilanan utilized a double-row scheme for planting rice seedlings. The spacing between the hills was set at 20 centimeters, with a meter separating each pair of rows. “With this ample distance, I cultivate sufficient azolla for both my rice production and other initiatives,” he noted.
In contrast to other farmers, he refrained from applying chemicals to his rice crops. As a proponent of Integrated Pest Management (IPM) – a strategy that enhances farm profitability while emphasizing insect and disease management with minimal pesticide application – he remarked that “beneficial insects” managed the pests on his farm.
“When my neighbors apply chemicals, the pests from their fields migrate to mine,” Fantilanan stated. “However, they do not linger – how could they, when they encounter all the spiders and beetles ready to consume them?”
Given the rising interest in organic farming, the Department of Agriculture, along with other governmental bodies, policymakers, and farmers themselves, should closely examine the benefits of azolla. “It is time to rediscover the numerous advantages of azolla,” Adang urged.
“Its high productivity associated with its ability to fix atmospheric nitrogen makes azolla an excellent green manure,” FAO said in a statement. “Its chemical composition makes it an important source of food for various livestock and special cultural practices made it possible to benefit simultaneously from its nutritive and fertilizing qualities, not to mention many other interesting properties of azolla.”
If composted alone, decomposition of azolla takes about two weeks. The Philippine Recommends for Organic Fertilizer Production and Utilization shares this procedure on how to do it: “Dig a pit and pile the azolla to the rim, or pile on the soil surface with bamboo fencing. Cover with banana leaves or plastic to prevent drying. Harvest in about two weeks. The recovery is 7-15 percent of the fresh weight.”
Aside from being a good source of nitrogenous fertilizer, azolla can also be utilized as feed for livestock.
Azolla is very rich in proteins, essential amino acids, vitamins (vitamin A, vitamin B12 and Beta- Carotene), growth promoter intermediaries and minerals like calcium, phosphorus, potassium, ferrous, copper, and magnesium, among others.
On a dry weight basis, azolla contains 25-35 percent protein, 10-15 percent minerals, and 7-10 percent amino acids, bio-active substances and bio-polymers. The carbohydrate and fat content of azolla is very low.
But azolla has limitations, too. Azolla culture essentially needs manual labor. Chinese scientists say it requires a lot of work, 24 to 33 man-days per hectare to produce 40 kilograms of nitrogen. It also requires a rather detailed management unfamiliar to most rice growers.
Furthermore, azolla must be propagated vegetatively in water year-round. “Azolla is particularly sensitive to a water shortage,” says Dr. Charles Van Hoe, one of the world’s leading experts on azolla. “Without water, the plant dies within a few hours.”
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