Vietnam, the world’s largest exporter of Robusta coffee, supplies 53% of the global market. However, this success comes at a significant environmental cost: decades of intensive cultivation have led to severe soil acidification and biodiversity loss, creating an ideal environment for soil-borne pathogens. A review in Agronomy for Sustainable Development by Long Nguyen Van and his colleagues, including Duy Nguyen Quang, Laetitia Herrmann, Aydin Enez, Lambert Brau, Chung Nguyen Van, Mathias Katz, and Didier Lesueur, explores the causes of this degradation and the potential of sustainable amendments like lime and biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More to mitigate these effects.

The primary driver of soil acidification in Vietnamese coffee plantations is the overuse of nitrogen-based chemical fertilizers. This leads to a decrease in soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, an increase in toxic metals like aluminum (Al), manganese (Mn), and iron (Fe), and deficiencies in essential nutrients such as phosphorus (P), calcium (Ca), magnesium (Mg), and potassium (K). The high annual precipitation in the Central Highlands, ranging from 1800 to 2000 mm, exacerbates these conditions through leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More. Soil pH levels in coffee plantations in the Central Highlands now range from 4.06 to 5.64, indicating strongly acidic conditions.

This acidification profoundly impacts soil health and coffee plants. It disrupts microbial ecosystems, reducing beneficial microbes and increasing pathogenic fungi (such as Cladosporium, Pyrenochaeta, and Exophiala) and plant parasitic nematodes (like Meloidogyne and Pratylenchus spp.). These pathogens are responsible for up to 40-50% yield losses and have led to the failure of approximately 40% of replanted coffee plantations in the Central Highlands. Soil acidity has caused populations of pathogenic fungi and plant parasitic nematodes to be 3-5 times higher than background levels.

The review highlights several soil amendments that can help restore soil health and suppress pathogens, including biochar, lime, organic fertilizers, mulching, and intercropping. Biochar, an alkaline, carbon-rich product from organic materials, significantly improves soil pH, physical properties, and microbial communities. Studies have shown that biochar application can increase soil pH by 0.03 to 1.17 units depending on the feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More and application rate. For instance, a 2% biochar application under greenhouse conditions increased pH by 1.1 units, while in field conditions, applications of 4, 8, and 16 t ha−1 raised soil pH by 0.18, 0.23, and 0.37 units, respectively, over two years. Biochar can also increase coffee yield by 17.2-24.5%, enhance soil porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More by 7.5-13.1%, and reduce harmful nematodes (Pratylenchus spp.) by 61.4-73.1% and Fusarium spp. by 23.6-32.1%.

Lime application is another effective method, increasing soil pH by 0.4 to 1.3 units with rates of 1.6-4.8 t ha−1. This improves soil structure, enhances nutrient availability (e.g., N, P, K), and immobilizes toxic heavy metals. Organic fertilizers from plant and animal residues improve soil physicochemical properties, increase organic matter, and promote beneficial microorganisms. Mulching with plant residues also alleviates soil acidification, reduces erosion, conserves moisture, and supports soil biological activities. Intercropping with other plants can improve soil pH and nutrient levels while controlling soil diseases.

Despite the promising benefits of these amendments, their effectiveness varies significantly with material type, application rates, soil properties, and ecological conditions. Challenges include limited resource availability, high costs for smallholder farmers, and potential negative effects if not applied correctly. The review concludes that optimizing the use of biochar, lime, and organic amendments is crucial for restoring soil health, controlling soil-borne diseases, and promoting sustainable coffee cultivation in Vietnam. Urgent action is needed to implement sustainable coffee farming systems to meet the increasing global demand for safe and green products.

Source: Nguyen Van, L., Nguyen Quang, D., Herrmann, L., Enez, A., Brau, L., Nguyen Van, C., Katz, M., & Lesueur, D. (2025). Restoring soil health from long-term intensive Robusta coffee cultivation in Vietnam: “a review”. Agronomy for Sustainable Development, 45(31).