Spatiotemporal variation in soil carbon-to-nitrogen and carbon-to-hydrogen ratios: a case study from agricultural farmlands in Southern Texas, USA

Introduction Soil elemental stoichiometry is the bedrock of carbon dynamics, and its understanding is essential in promoting soil carbon sinking capacity. Methods This study examined the spatiotemporal variation of soil carbon-to-nitrogen and carbon-to- hydrogen ratios in agricultural farmlands at Prairie View A&M University. The soil C:N, C (%), and C:H were measured and quantified in three different arable farmlands across two depths (top- and subsoils). Result The results reveal that the percentage of carbon was higher in the topsoil and lower in the subsoil. C:N and C:H ratios equally followed the same pattern, with plot 3 recording the highest amount in each of the elemental stoichiometry recorded levels. C:H–C:N ratio relationships were positively correlated with each other, indicating variations in soil organic matter composition and dynamics. Their positive correlation sheds light on the abundance of carbon-rich, low-nitrogen organic matter in the topsoil and nitrogen-rich organic matter in the subsoil. C:H ratio equally followed the same trend. Interestingly, the soil pH in our study, which is a key driver in microbial mineralization of organic matter in the soil, occurs within the optimum ranges of 6.0 to 7.5. Additionally, the elemental composition ratios in this study was high, but when compared with various organic matters of plant origin, it appears to be very low, showing high microbial activities in the decomposition of the carbon matter. This decomposition process is supported by the observed conducive soil pH. Discussion Overall, these findings confirmed that the agricultural farmlands in our study sites are very weak in carbon sequestration and necessitates the adoption of measures such as biochar or soil conditioners/amendments application that is capable of modulating soil conditions and promoting carbon storage in the soil.