Real-time assessment and measurement of soil carbon in agricultural land of Gloucestershire at a farm-scale

Previous research promoted carbon assessment and flow of human and natural capital to remediate atmospheric carbon emissions on farms. However, differences among types of agricultural land are often not included as part of measurement methods. This study collected soil and plant measurements for 530 field samples in Spring 2023 to compare levels of soil organic carbon (SOC) among different agricultural land uses across Hartpury and Cirencester, Gloucestershire using real-time near-infrared spectroscopy (NIRS) analysis. SOC was expressed as g/kg, t/ha and ratio to soil clay content. A higher percentage of permanent grass and woodland areas were classified as having good and satisfactory SOC/clay ratio compared to arable and temporary ley fields. Permanent and woodland areas also had higher mean SOC (g/kg), total nitrogen (g/kg), soil , carbon (t C/ha), nitrogen (t N/ha) and soil moisture (%). Although arable and temporary ley fields were more productive with a greater herbage height (7.1 cm and 6.3 cm respectively) and biomass cover (7073 kg FW/ha and 6839 kg FW/ha respectively) than permanent grass fields (4.5cm and 6199 kg FW/ha), permanent grass fields still had significantly better levels of SOC, nitrogen, as well as other critical soil and plant properties such as SOC/TN ratio, TN/Clay ratio, plant fresh density (kg FM ha−1cm−1), dry density (kg DM ha−1cm−1), ash, acid detergent fiber (ADF), neutral detergent fiber (NDF) and protein (all in g/kg DM). This study shows that NIRS can serve as a user-friendly and practical alternative for large scale measurements to monitor soil and plant properties among agricultural land uses. Further work is needed to evaluate the NIRS measurements against standard measurement approaches across a range of soil and plant type to support large scale field monitoring.