Bounyoung Doungpanya, a farmer in Attapeu, Lao PDR, once owned many buffalo and used their manure to fertilize his fields. When tractors and agricultural technology replaced the need for livestock to plow paddy fields, he relied on market fertilizers.
Over time, he noticed that the quality of his soil declined. Many areas became so poor that he left them uncultivated because investments did not bring returns.
When the rice harvest ends, Doungpanya’s paddy fields fall silent and empty, waiting months for the next rainy season to come again. Many of Doungpanya’s neighbors, also rice farmers, turn their energy to cassava plantations in upland areas, a high-yield crop with strong market demand.
Across Lao PDR, farmers are grappling with declining soil quality. Mono-cropping systems and chemical fertilizers have placed increasing pressure on soil fertility. Without substantial crop rotation or organic inputs, these cash crops extract valuable nutrients from the soil.
In 2024, the International Water Management Institute (IWMI), together with the French Agricultural Research Centre for International Development (CIRAD), began research on an important question: Is there an affordable, climate-friendly way for farmers to restore Lao PDR’s soil health?
Assessing soil health
In January 2024, IWMI and CIRAD went to Attapeu Province to understand what was happening beneath the soil’s surface. Researchers collected soil samples from eight villages, analyzing soil health indicators from microbial diversity to chemical properties.
The data revealed that the soil in Attapeu was predominantly sandy, acidic and had extremely low carbon content. Without regular inputs of organic matter to maintain soil fertility, sandy soils tend to quickly lose their carbon — especially under tropical conditions. This leads to invisible soil degradation such as soil compaction, in turn limiting plant growth and degrading the conditions needed for a healthy soil ecosystem.
These preliminary observations were a wake-up call. IWMI and CIRAD researchers began searching out sustainable, nature-based and low-cost solutions to restore soil fertility. The goal was to provide alternatives to mono-cropping, build local soil knowledge and propose realistic agroecological practices for Lao PDR farmers.
Introducing legumes for soil improvement
Legumes are plants from the Fabaceae or pea family, which includes more than 19,000 species worldwide. A special characteristic of legumes is their interaction with the soil bacteria rhizobium — crucial for fixing atmospheric nitrogen, a vital nutrient for plants. Nitrogen-fixing plants like legumes are used as cover crops to naturally improve nitrogen content in soil and are known as “green manure.” Therefore, when legumes are cultivated before or after cash crops, they enrich the soil.
Researchers proposed a farmer-led experiment, spanning two years, to test different legume varieties and build awareness and adoption of legumes as a soil-enriching technique.
Farmers tested three to five legume species on small plots. The species included butterfly pea, rattlepod, stylo, mung bean, peanut and cowpea. Each farmer also received financial support of about 1,000,000 Lao Kip ($50) to cover partial costs for soil preparation, irrigation pipes, fertilizer and labor.
During the first year, three farmers, including Doungpanya, participated in the pilot. All three had promising results with stylo, rattlepod and mung bean varieties growing well. Mung beans provided both soil cover and edible seeds that farmers could sell, allowing them to earn some income while improving soil quality.
During the experiment’s second year, from 2025 to 2026, two farmers continued and two new ones joined. The farmers doubled the size of the legume plots and introduced a broader selection of legumes with support from the Alliance of Biodiversity and International Center for Tropical Agriculture (CIAT). Based on farmer preference for income-generating crops, they planted mung bean, Ochroleuca, cow pea, butterfly pea and peanuts.
The soil analysis from both years showed that integrating legumes into rice systems can help improve soil balance, particularly soil pH and nitrogen, which are important for sustainable rice production over time. For example, rice–legume fields had a wider and generally higher pH range of 5.2–7.5, compared with the rice-only soil pH range of 4.6–6.0. This suggests that legumes as a cover crop improved soil conditions, bringing pH levels closer to the optimal range for rice cultivation between 5.5 and 7.0. Additionally, total nitrogen in rice–legume soils reached up to 0.07%, which is slightly higher than mono rice (up to 0.06%), indicative of the contribution of legumes to soil fertility.
Interestingly, the two experienced farmers performed better, likely due to improved management and experience gained from the first year, highlighting the cumulative impact of capacity building.
However, while these shifts point in a positive direction, the magnitude of change remains modest. Compared to reference thresholds for well-balanced, productive soils, the improvements in nitrogen and other nutrients are incremental rather than transformative, suggesting that longer-term or more intensive integration of legumes may be needed to achieve significant gains in soil fertility. Additional soil management practices, such as better nutrient recycling and use of organic matter, should also be considered to further improve soil quality.
Soil becoming “poupui”
After joining the legume experiment, Doungpanya observed gradual changes. Although yield increases were not yet significant, he described his soil as becoming more “Poupui,” a local term meaning good soil; “the soil felt softer and less compacted than before, and crops appeared much healthier.”
Dounpanya and his family plan to continue planting legumes even after the project concludes. He wants to integrate legumes with other crops, combined with improved water management for best results.
During the experiment, farmers also tested their own innovations by planting legumes with other crops, such as butterfly pea alongside eggplant, and cowpea with tomatoes. The crops grown together appeared to perform better than those grown as single crops — and the idea came directly from the farmers themselves.
Over the two-year project, IWMI learned from field- and farmer-led research that science is only half the battle. Out of economic necessity, farmers prioritize immediate income over long-term sustainability. Convincing a farmer to integrate legumes instead of high-earning cash crops like cassava is a significant challenge and requires more than just scientific knowledge and statistics — it requires people-to-people communication and relevant, accessible discussions on how crop diversification will improve their farms and lives.
Looking forward to resilient fields
The journey of introducing legumes in Attapeu, Lao PDR is just at its infancy. The changes are still small, not yet visible across the wider landscape, but in the hands of our pilot legume farmers, something is quietly shifting. The soil feels healthier; crops look greener and more alive.
These early signs may not yet appear statistically significant, but they are powerful in the eyes of those who work the land every day. If legume farmers continue to improve their practice and management in the coming seasons, if yield strengthens and soil continues to recover, the practice can naturally spread from one household to another. In rural communities, real change travels through observation and trust, strengthening farmer-to-farmer learning: when farmers see success in the fields of another with their own eyes, they follow suit.
Legumes may not replace major cash crops, but they offer a pathway toward healthier soil and more sustainable livelihoods for the people of Attapeu. These small experimental plots have the potential to become a wider movement toward more resilient farming systems across Laos.
Ammala Chanthalath is a research officer at IWMI, Mark Dubois is the IWMI country representative for Lao PDR, Joshua Philp is a scientist with the Tropical Forages Program, Alliance of Biodiversity and International Center for Tropical Agriculture (CIAT), and Florine Degrune is a soil scientist with the French Agricultural Research Centre for International Development (CIRAD).
