Remote sensing of cover crop legacies on soil health and main crop N-uptake dynamics

Sustainable management of arable cropping systems requires insight into the temporal dynamics and spatial variation of crop performance to minimize nutrient losses and enable soil health-based precision agriculture. In arable systems, growing cover crops is a tool to promote soil health as they enable nutrient retention in autumn/winter and provide nutrients in spring/summer to the main crop upon cover crop mineralization by the soil biota. However, different cover crop monocultures and mixtures affect the soil biology and nutrient dynamics differentially due to the variation in quantity and quality of the plant material returned to the soil. To understand the legacy effects of cover crops on the main crop we need high resolution data of the crop responses to soil health conditions throughout the growing season. Remote sensing can provide such high-resolution data yet requires solid parameterization before it can be operationalized. Here we studied the temporal dynamics of soil nitrogen (N) availability and N uptake in barley in response to the soil legacy of different cover crops. We used high-resolution multispectral images of the main crop acquired from a Unmanned Aerial Vehicle (UAV), and in situ collected plant and soil parameters in a long-term field experiment with eight different cover crop treatments. The cover crop legacies significantly affected N uptake, biomass, and canopy chlorophyll content (CCC) in barley, with highest values in barley grown after vetch-radish or oat-radish and lowest in barley on fallow or oat legacy plots. The temporal dynamics of N-uptake throughout the barley growing season revealed that cover crop legacy effects became apparent/distinct by the end of stem elongation. This work demonstrates the potential of remote sensing to monitor and understand temporal and spatial variation of crop canopy traits in response to cover crop induced soil health legacies. This approach can contribute to more efficient N use by enabling fine-tuning of the quantity, timing, and location of fertilization.