Research Objective
A Normalized Difference Vegetative Index (NDVI) risk map was created that correlated with the amount of Aphanomyces DNA in the soil, but drought was a major source of error in the risk map.
Overall, the high-risk areas on the map had the highest presence of Aphanomyces DNA averaged across the soil samples, followed by medium risk, and then low risk, with no DNA present. Some areas mapped as high- and medium-risk contained no Aphanomyces DNA in the corresponding samples. NDVI images were used to measure colour differences in the field. Areas falsely detected as high risk were actually yellowing and stunting caused by drought, not Aphanomyces symptoms.
NDVI risk may be more accurate in years of average to above-average rainfall, when drought symptoms cause less interference. Areas with high weed populations should also be considered when constructing risk maps.
The elevation risk map and yield monitor map created using data from the combine showed no relationship between either elevation or yield and Aphanomyces DNA presence in the field.