The short-term effect of coffee husk biochar application in acidic soils on soil properties, root mycorrhization, pest, and disease management and yields in Robusta coffee and black pepper plantations in Gia Lai province, Vietnam

Vietnam is the world's leading exporter of Robusta coffee and black pepper. However, the widespread use of intensive cultivation practices has contributed to progressive soil acidification and an increasing incidence of soilborne diseases, threatening the long-term sustainability of these high-value crops. This study evaluated the short-term effects of applying coffee husk-derived biochar (2.5 t ha −1 ) on soil quality, pathogen suppression, and crop performance in acidic soils of coffee and black pepper farms in Gia Lai province. Over the course of 1 year, key soil physicochemical and biological properties, soilborne pathogen populations, and crop yields were monitored. The overall impact of biochar at this application rate was limited, and most differences between treated and untreated plots were not statistically significant ( p < 0.05). The study found that biochar application could lead to slight and promising improvements in soil conditions, including modest increases in nutrient availability, soil pH, and arbuscular mycorrhizal colonisation of plant roots. Reductions in specific pathogen populations, particularly plant-parasitic nematodes and Phytophthora spp., were also observed. These findings suggest that while biochar holds promise as a sustainable soil amendment, it requires more time than a single season to deliver substantial agronomic benefits. Additionally, future research should explore higher or repeated application rates, assess medium- and long-term effects, and investigate how biochar can be integrated with complementary biological or ecological soil management strategies to enhance its effectiveness in improving soil health and reducing disease pressure in perennial cropping systems.