Turning agricultural by-products into 'biological shields'

Healthy soil, strong crops

At the La Huong vegetable area (Cam Le Ward, Da Nang City), piles of discarded vegetable stems and leaves after each harvest are no longer gathered, dried, and burned as before. Instead, farmers collect them as raw materials to produce organic fertilizer for the next vegetable crop.

Mr. Mai Van Phu, a producer in the La Huong safe vegetable area, said that about two years ago, farmers in the region attended training classes organized by officers from the Da Nang Biotechnology Center (Da Nang Department of Science and Technology). They received direct guidance on processing agricultural by-products into organic fertilizer, along with support for microbiological preparations to implement the model. After the program ended, local farmers mastered the technique and have maintained production until now.

"Previously, the officers guided us very meticulously, from processing raw materials and mixing microbiological preparations to monitoring the composting process. Now we can do it all ourselves, no longer relying on external support. Thanks to this, we save a significant amount of money buying chemical fertilizers every crop. If I used to buy 150 bags of fertilizer per year, now I only need to buy 30 bags," Mr. Phu shared.

According to Mr. Phu, the composting process is not overly complicated. After each harvest, fresh vegetable stems and leaves are collected, cleaned, chopped, and treated with lime before being mixed with microbiological preparations, molasses, and several essential nutrients. Depending on conditions, farmers can supplement with chicken manure or oil cakes to increase nutrient content.

After about 45 days, all by-products decompose into organic fertilizer, ready to return and nourish vegetable beds in the new crop. Each year, his family produces about 10 tons of organic fertilizer, nearly enough to fertilize over 4,000 m² of vegetables and crops. "In the past, looking at piles of by-products, I only saw garbage. Now, it is a precious source of fertilizer for the entire next crop," Mr. Phu smiled.

What keeps farmers attached to this method is not only reduced production costs, but also noticeable changes in the fields. Cultivated soil is increasingly porous, retains moisture better, plant root systems develop strongly, and crops grow more stably.

"The soil is looser, plants take root quickly, and grow strongly. Most noticeable is broccoli: previously, fertilizing with chicken manure combined with NPK and urea, plants often suffered from soft rot disease. Since switching to organic fertilizer, plants are stronger, and disease has decreased markedly. Beneficial microorganisms thrive, helping restrict harmful bacteria, so plants suffer less disease," Mr. Phu stated.

Not only in the La Huong vegetable area, but many farmers across Da Nang are also step-by-step shifting to utilizing agricultural by-products to produce organic fertilizer. Mr. Mai Thanh Quang, who produces at the Tuy Loan Safe Vegetable Cooperative (Hoa Vang Commune), began applying this model in 2025.

According to Mr. Quang, microbiological organic fertilizer not only helps maintain long-term soil fertility and ensures strong, stable crop growth but also reduces external fertilizer purchase costs by about 80%.

"More importantly, the soil is nourished sustainably, plants are stronger, and growers gradually reduce reliance on chemical fertilizers. Thanks to that, produced items are safer for consumers," Mr. Quang shared.

Reducing 70% of fertilizer costs

According to Ms. Nguyen Thi Ly Na, an engineer at the Department of Applied Science and Incubation - Da Nang City Department of Science and Technology, burning straw and post-harvest stems and leaves still occurs in many places, causing environmental pollution while wasting organic resources. From that reality, the Da Nang Biotechnology Center implemented science and technology tasks applying microbiological preparations to turn agricultural by-products into organic fertilizer right in local areas, contributing to reducing production costs, improving soil, and developing circular agriculture.

According to Ms. Ly Na, microbiological organic fertilizer not only provides nutrients, but also helps restore beneficial soil microflora. When the soil is healthier, crops develop greater natural resistance, limiting diseases such as root rot and soft rot, thereby reducing the need for crop protection chemicals. Simultaneously, fertilizer costs decrease by about 70% compared to using entirely chemical fertilizers.

"The greatest value of the model lies not in the amount of organic fertilizer created, but in the shift in farming mindset. Farmers no longer view discarded stems and leaves after harvest as trash to be burned but instead consider them resources for regenerating soil, nourishing plants, and gradually reducing dependence on chemical fertilizers and crop protection chemicals. The model will continue to be replicated across cooperatives and concentrated production areas to spread green, low-emission farming methods while effectively utilizing agricultural by-product sources," Ms. Na stated.

Mr. Le Tu Tuan, Head of the Da Nang City Sub-Department of Crop Production and Plant Protection, stated that the city is actively promoting agricultural development toward an ecological, climate-resilient, and low-emission orientation. The agricultural sector prioritizes solutions that apply biotechnology, use organic fertilizers, and employ integrated pest management to enhance agricultural produce quality, reduce environmental impacts, and protect producers' health.

"In the coming time, the city's agricultural sector will continue to coordinate with research institutes, universities, enterprises, and international organizations to transfer technical advances, promote circular economy in agriculture, utilize by-products to produce organic fertilizer, gradually reduce dependence on chemical fertilizers and pesticides, toward green, safe, and sustainable agriculture," Mr. Tuan stated.

To bring the model into reality, farmers receive support with microbiological preparations and essential materials, along with on-field "hand-held" guidance. Thanks to this, after implementation, locals have mastered the protocol, proactively producing organic fertilizer from their own by-product sources.

The model's efficiency is clearly reflected through numbers. In 2023, models processed approximately 34 tons of by-products, generating about 13 tons of organic fertilizer; in 2025, they continued processing 21 tons of raw materials, producing about 8 tons of fertilizer to serve production.