ASHS 2025 Conference

Soil organic matter (SOM) is a key determinant of soil health, directly influencing structure, moisture retention, nutrient availability, and microbial activity. Among soil amendments, biochar has gained attention for its potential to enhance soil fertility and support plant productivity. However, its influence on citrus root system architecture and nutrient uptake across different rootstocks remains underexplored. This study evaluated the effects of four biochar concentrations (0%, 10%, 20%, and 30% v/v) mixed with native field soil on four citrus rootstocks: ‘Sour Orange’, ‘Swingle’, ‘US-802’, and ‘US-942’. Plants were grown under controlled greenhouse conditions for 16 weeks. Root system architecture traits: total root length, surface area, root volume, and number of forks, were quantified using WinRHIZO™ analysis. Soil parameters, including pH, cation exchange capacity (CEC), moisture content, and SOM, were assessed post-harvest, alongside plant tissue nutrient concentrations (P, K, Ca, Mg, Mn). The 20% biochar treatment significantly enhanced root morphological traits across all rootstocks, with increases of up to 35% in total root length and 40% in surface area compared to the control. Plant tissue analysis revealed elevated macro- and micronutrient concentrations in the 20% treatment, particularly for P, K, Ca, and Mg. Soil analysis showed progressive improvements in pH, SOM, CEC, and moisture content with increasing biochar concentration, with the highest values recorded at 30%. While higher biochar rates improved soil physicochemical properties, the 20% concentration provided the most balanced benefits, optimizing both root development and nutrient uptake. These findings suggest biochar, particularly at moderate rates, may be an effective amendment for improving soil fertility and citrus root system performance in nutrient-limited soils.