Monday’s derecho event took a toll on crops across Iowa. Satellite imagery shows millions of acres of Iowa crops impacted by the high wind events. As growers dig out from the destruction left after the storm, decisions regarding how to manage the impacted crop will be front and center.
For wind damaged corn, the decision about how to manage the crop will largely depend on if the plants are bent over or snapped off. Plants that are bent can still transport water and nutrients. These plants should continue to mature, although at a slower pace. Plants that are broken or snapped below the cob will result in plant death.
UAVs are an effective tool to help assess the magnitude of damage in a field and determine if stalks are leaning or snapped off. UAVs have become prevalent within agriculture networks in the past few years and many neighbors, ag retailers or crop consultants have access to UAVs that can help evaluate crop damage.
A Bird’s Eye View image can provide a quick look at the extent of crop damage in your field (Figure 1). Anywhere you can’t visually “row the corn” indicates areas of crop damage. You will also normally notice downed corn has a lighter color as the lower side of corn leaves and stalks will reflect light differently. While this view provides an effective early indicator, it does not allow you to calculate the total area of impacted crops.
Figure 1: A Bird’s Eye View of crop damage caused by high wind events. This view can define the general scale of the impacted crop in a field.
UAVs can also support a Close Up View of crop damage in parts of a field that would be difficult to scout given the conditions. This includes flying out to regions of a field not visible to get a better look at the magnitude of crop damage (Figure 2 and 3). Additionally, by adjusting the camera angle towards the base of the plants, the imagery can help determine the extent of green-snap present. These views are helpful both in making immediate decisions regarding crop health and in monitoring the crop health and dry down as the season progresses.
Figure 2: A Close Up View of crop damage caused by high wind events. In this example the corn is leaning but has not snapped off.
Figure 3: A Close Up View of crop damage caused by high wind events. In this example the corn is snapped below the ear which results in total plant death.
A Full Field Map can be created by stitching together several individual UAV images (Figure 4). Creating a Full Field Map will take more time and require the entire field to be flown in a pattern by the UAV. The primary advantage to this method is that you can use web tools to estimate the area of a field that is impacted. This will be helpful in the areas of Iowa along the edge of the derecho where only a portion of a field suffered crop damage.
Figure 4: A Full Field Map of crop damage caused by high wind events. This view allows for measuring the area of impacted crops and is helpful in assessing damage in a partially impacted field.