Utilizing fermented kitchen waste to improve ragworm ponds

9 years of fermenting kitchen waste with probiotics

At this time of year, all the ragworm ponds are being drained and left to dry, exposing their brownish-gray muddy bottoms. Pham Thi Phuong, owner of a ragworm pond in Hamlet 3, Vinh Thuan commune, Hai Phong city, said that the ragworm pond is supplemented with probiotics, giving the soil a brownish-gray color with a golden hue while making it looser.

Over 10 years ago, this area was covered by rice fields. Then, as the price of this invertebrate species rose to VND 500,000-600,000/kg, some pioneering households began converting rice fields into ragworm ponds. In 2021, Phuong's family bought six sao (360 m²/sao) of a ragworm pond along the Luoc River from an elderly family.

In reality, ragworm farming is simply about creating the best environmental conditions, such as applying composted chicken manure and cornmeal to enrich and loosen the soil, thereby providing favorable conditions for the ragworms to reproduce and thrive, rather than supplying them with any specific type of feed.

Some farmers also take extra care to apply microbial fertilizer to their ragworm ponds to nourish the soil. Since these products all rely on microorganisms, Phuong decided to experiment by applying her family's kitchen-waste compost fermented with Emuniv probiotics.

Previously, when she was still a member of the Commune Women's Union, Phuong had pioneered in using microbial technology in 2017, when a program promoting the treatment of kitchen waste into fertilizer for crops was introduced in her hometown. Every year, she composted tons of kitchen waste to fertilize her family's garden, where the plants grew vigorously. In 2021, after acquiring the ragworm pond along the Luoc River, she began experimenting with applying the microbial compost to improve the pond bottom.

Specifically, in January, she tills the pond surface, then applies microbial compost, rice husks, and rice straw, and thoroughly compacts the mixture by foot. The microorganisms not only loosen the soil but also break down plant and animal residues, including dead ragworms, preventing the soil from becoming toxic. In April, she adds crushed corn kernels. In June, she applies additional composted chicken manure. Ragworm eggs are found both in the field soil and in the tidal water flowing into the pond. Under favorable conditions, they will develop into ragworms.

Like rice, ragworms also have two growing seasons: the winter-spring crop from February to April on the lunar calendar and the summer-autumn crop from September to December on the lunar calendar. As the living environment has improved, ragworm yields from Phuong's six-sao pond have steadily increased over time. In the first year, she harvested 80 kg, with a selling price of VND 380,000/kg. In the second year, the yield reached 450 kg, sold at VND 320,000/kg. The third year produced 600 kg, sold at VND 260,000/kg. In the fourth year, she harvested 900 kg, selling them at a price of VND 220,000/kg. By the fifth year, the yield had reached 1,200 kg, although the selling price had fallen to VND 150,000/kg.

Ragworm prices fall, but profits remain high

Ragworm prices have never been as low as they are this year, at just VND 150,000/kg. Nevertheless, Phuong still earns a profit equivalent to half of her total revenue. Ragworm output from her pond treated with microbial preparations is only on par with that of conventional ragworm ponds, but she saves around VND 2-3 million/year by not having to purchase microbial fertilizer. More importantly, the soil and water environments have improved in a more sustainable direction.

Based on these practical results, 5-7 households in Vinh Thuan commune have now followed Phuong's model and adopted microbial ragworm farming. However, most farmers still use traditional methods. Some even leave the areas along the pond banks unweeded and instead opt to spray herbicides because it is faster and more convenient. What concerns Phuong is that a large commune dumpsite that has existed for many years is located right at the entrance to the ragworm pond area.

MSc. Bui Thi Hong Ha from the Organic Agriculture Division under the Center for Agroecology Research and Vocational Training at Viet Nam National University of Agriculture commented, “Phuong is passionate about and persistent in recycling kitchen waste for use in ragworm fields. However, relying solely on her to encourage local farmers through word of mouth has not been very effective. Therefore, the State’s support policies are needed if the model is to be expanded.”

In reality, technology does not always outperform personal connections. Some companies offer probiotics at very low prices, but those products are intended only for treating septic tanks and can handle limited volumes. There are also homemade microbial technologies promoted as costing nothing because they are made by mixing ingredients such as yogurt and various digestive enzymes. However, a closer calculation shows that they can be quite costly. Moreover, homemade microbial preparations are not suitable for commercial-scale farming because they lack stability.

“Our Emuniv microbial preparations include two product lines: one for treating rice straw in paddy fields and the other for treating livestock waste and organic waste. When conducting training sessions on their applications, I usually take two buckets of mud from the same field. I add a spoonful of microbial products to one bucket and nothing to the other, then add water and knead the mud. After an hour, I have the trainees knead the mud in both buckets themselves, and they can see the difference. The mud in the bucket containing microorganisms is softer and finer because the particle size has changed and the soil aggregates have broken down, eliminating the clayey condition. With microorganisms, even when the soil is dry, it does not become hard and compacted,” MSc. Bui Thi Hong Ha said.

In addition to the microbial ragworm model in Hai Phong, several years ago, the Center for Agroecology Research and Vocational Training also coordinated with the former Thai Binh Agricultural Extension Center to apply the approach to rice-ragworm farming among several dozen households. The results showed that ragworm yields increased year after year, as nutrients gradually accumulated in the soil, creating increasingly favorable conditions for ragworm development.

$ 1 = VND 26,480 - Source: Vietcombank