This one-meter resolution image of farmland in central California illustrates the effect of a disease known as "clubroot" on a cauliflower crop.

Displaying Digital Aerial Images using the Infra-Red Color Bands Makes the Crop’s Characteristics Easily Visible to the Naked Eye

Clubroot is a soil-borne disease, and as such, will not spread to neighboring crops unless the contaminated soil is shifted or spread (e.g., through equipment that is not cleaned between uses) to another location. The common remedy is to till and treat the soil before the next growing season begins. Then, clubroot can be effectively managed by raising the pH level with the application of lime.

Crop consultants investigating this field on foot were able to detect the presence of clubroot. However, the extent of damage due to the disease had not been recognizable. High-resolution multi-spectral imagery, such as the image displayed here, can help the consultants and the grower recognize the extent of clubroot disease and help prevent it from re-occurring during the next growing season.

The grower was faced with the decision to either destroy the crop and forfeit revenues, or to harvest unaffected areas and sell those portions which were still healthy.

Since cauliflower is a valuable crop, pricing out at roughly $3,616 per acre, the grower decided to harvest the crop and sell the portions that were unaffected by clubroot, even though his yield was significantly reduced. Since approximately 8.5 of the 17.7 acres were affected by the disease, the potential loss on the damaged portion alone could have reached more than $30,700.

The grower still must remedy the problem caused by clubroot disease. After harvesting, the grower may prepare the affected soil for the next growing season by treating it with lime, thereby preventing the disease from reoccurring.

Here, polygons delineating vegetation stress are automatically generated in the grower's information system, mapped to a coordinate grid system, and input to a variable rate applicator. This enables the grower to determine precisely which sections have the highest and lowest incidence of affected soil, thus enabling him to apply the proper treatment. "Treatment A" refers to the soil areas which have experienced the least damage and where the application of lime should be less concentrated. "Treatment B" indicates that a higher concentration of lime is required.

This "image map", which combines both aerial imagery and the line map, has been color-coded to demonstrate the actual use of the land vs. how the land has been zoned. This information, obtained by querying a city database to determine land use classification, would be useful for local governments planning for future growth needs, such as infrastructure.

The additional information provided by the underlying aerial image helps developers and city planners determine what land zoned for single family detached housing is still available for development. Overlain with vector data, this imagery also helps developers make an easy visual distinction between land that has been zoned for single family detached housing and land that has been zoned for something else.

It is also useful for determining which properties have higher value and why. For instance, in a line-drawn map, a prospective property owner might not realize why the property he is considering has such a high price tag. Looking at the image of the same area, he instantly realizes that the property is "lake-front" which automatically gives it a higher property value.