Biochar Influences Soil Health and Nutrient Dynamics in Row Crop Production Systems

Abstract

Most soils in Alabama are Ultisols, which are characteristically highly weathered, low in organic matter, and inherently low in fertility. The introduction of biochar to these soils as a soil amendment has the potential to increase soil health, which would be beneficial to Alabama producers. Biochar is organic matter that undergoes pyrolysis, resulting in a highly charged, highly stable source of carbon. However, it is an expensive soil amendment, and further research is required to under-stand how biochar will affect soil health and crop production in Ultisols. An ongoing research study was initiated at both the Wiregrass Research and Extension Center in Headland, Alabama, and the Tennessee Valley Research and Extension Center in Belle Mina, Alabama, to investigate the impact of varying biochar application rates (0, 3.5, 7.0, and 14.0 Mg ha-1) in combination with cover crops on soil health within crop production systems. The study utilized a randomized complete block design with four replications. Soil samples were collected to a depth of 60 cm in spring 2024 and 2025 following the termination of cover crops. Chemical indicators assessed included pH, Mehlich 1-extractable plant nutrients, soil organic carbon, inorganic N, and permanganate oxidizable carbon. Physical indicators measured included bulk density and wet aggregate stability. Biological indicators measured included microbial biomass carbon and soil res-piration. Additionally, agronomic factors such as tissue nutrient uptake and yield were evaluated. The highest biochar application was observed to have the most influence on soil health pa-rameters. Soil organic carbon in the top 5 cm of soil increased by 64% at WREC and 17% at TVREC when 14 Mg ha-1 biochar was applied. For every 1 Mg ha-1 of biochar applied, carbon sequestration increased by 0.348 Mg ha-1 at WREC and 0.301 Mg ha-1 at TVREC. Minimal effects were observed at deeper depths for both locations. Surface soil pH increased slightly at WREC, but not at TVREC, when 14 Mg ha-1 biochar was applied. A year and a half after application, biochar had minimum influence on soil nutrient content, biological soil properties, and physi-cal soil properties. Biochar did not affect cotton yields at either location; however, cover crops re-sulted in an 8% increase in cotton yield at WREC compared to fallow. Biochar rarely interacted with cover crops to influence soil health indicators and agronomic factors. More time is required to thoroughly investigate the full effects of biochar and its potential impacts on soil health, as well as the effects of cover crops and biochar on soil health.