Using remote sensing for monitoring of autumn tillage in Norway

Management systems on agricultural land in Norway are causing concern because of increasing area wide soil erosion, consequent increase in sediment loads and nutrient losses to waters, and their consequent pollution. Monitoring of areas in autumn is important because this is the start of a season when much of the erosion occurs. This is often caused by management systems in autumn, but also because climatic conditions in this season are important for erosion processes. We have investigated several sources of remote sensing data, with a view to assembling the best overall monitoring system for this geoscience problem. The sources were digitised CIR (colour infrared pseudocolour) aerial photography, SPOT and ERS-1 SAR. CIR photography proved more accurate than SPOT data, especially with regard to exposed soils as result of CIR's continuous spectral sensitivity. We found that SPOT is clearly limited as a monitoring tool for soils and there is a need for better sensors in range 680 to 790 nm wavelengths. ERS-1 SAR provides information when the optical sources cannot, but is dependent on good digital elevation models. We found that the most effective monitoring is done using a combination of microwave and optical sources.