INFRARED SPECTROSCOPY FOR SOIL CARBON ACCOUNTING AND SOIL QUALITY ASSESSMENT

The future of global food security and economic stability continue to raise increasing concern, as the human population and thus demand for agricultural resources are rising at an alarming rate, while the frequency of extreme weather events leading to drought, flooding, and heat stress are projected to increase. Furthermore, the impacts of climate change on crop productivity and water availability are already apparent, and if current trends of increasing atmospheric CO2 levels and land degradation persist, the stability of whole food systems could be at risk. Building soil organic carbon (SOC) is essential for restoring degraded soils and enhancing soil health, as increasing SOC can reduce compaction, improve drainage and aeration, increase water holding and cation exchange capacity, and enhance nutrient cycling and fertility, thereby improving agronomic productivity and resource use efficiency in agroecosystems. Implementing soil management practices to build SOC can provide win-win opportunities for farmers and resource managers, resulting in improved soil health, increased fertilizer use efficiency, and increased resiliency to drought and heat stress, while serving to mitigate climate change by sequestering atmospheric carbon. However, the excessive sampling and analysis costs required to measure baseline levels and monitor changes in soil quality, currently limits our ability to establish effective policies for incentivizing sustainable soil management practices. Mid infrared (MIR) and visible and near infrared (VNIR) spectroscopy have been proposed as accurate and low cost options for predicting multiple soil quality indicators, and may be capable of meeting current needs of a low cost reliable method for quantifying soil quality and SOC. In this dissertation, I explore potential applications for MIR and VNIR spectroscopy by developing and testing low-cost, reliable measurement-based approaches for quantifying soil quality and SOC at farm-to-regional scales. Both VNIR and MIR spectroscopy successfully predicted SOC and other soil quality indicators with an acceptable level of accuracy often comparable to that of standard wet chemistry methods for soil assessment, yet measurement costs for both VNIR and MIR predictions was roughly an order of magnitude less than standard wet chemistry methods