Can in-field NIR spectroscopy provide an option for soil carbon monitoring?

Current soil sampling methods are expensive, time consuming and destructive. These constraints result in a standard practice that combines samples from a W transect across a field, into one composite sample for laboratory analysis. This presents a challenge for farmers, policy makers and industry, as this method of sampling doesn’t give the required detail about the variability of soil properties across the field. The heterogenous nature of soil means that differences between monitoring results across years could be due to changes in sample location, and the natural variability of the soil. This is of particular concern for farmers and policy makers monitoring soil carbon under the transition to sustainable farming methods, as they want to be sure that the change they see is due to management changes, not inherent variability. Simple, handheld, near-infrared (NIR) spectroscopy devices can be used in the field by practitioners. They are cheap, quick and non destructive. This allows for more samples to be taken across a field, and GPS allows repeat sampling of the same location over time. This paper looks at how accurate in-field soil spectroscopy performs compared to laboratory results, how variable soil properties are across a field, and how different sampling methods (W transect, random sampling) capture that variability.