For a couple of years, some Iowa farmers have noticed lower yields along the southern and/or western edges of their fields. The low yields along the border tend to be prevalent when soybean, hay, or pasture are growing adjacently to the field on the southern or western edge. This phenomenon tends to be more prevalent during less desirable growing seasons when the weather is rather hot and dry. Some believe herbicide drift from adjacent fields could be the culprit for the lower yield. However, scouting reports do not always support this conclusion. The phenomenon may also be due to a combination of the corn microclimate and weather patterns where air passing over and entering the corn canopy is initially drier at the field edge and, due to plant respiration, the air collects more moisture as it passes further into the field.
For this project, we have selected several corn fields with soybean growing along the southern and/or western edges. Each field chosen is considered to be relatively uniform in topography and a single hybrid planted. Each field contains 2 to 4 transects extending into the field to approximately 200 feet. Within each transect, 4 temperature and relative humidity sensors are placed within the canopy to collect data throughout the growing season. Before combine harvest, the sensors will be collected as well as hand harvesting 10 ears from each sensor location in a transect. The hand harvested ears will be analyzed for yield components such as the number of kernel rows, number of kernels per ear, and individual kernel weight. The Yield data from each field collected by the combine yield monitor at harvest will allow us to determine if there is potential grain yield and individual yield component gradients happening in the field along the southern and western sides.
Light reflectance data is also be collected from field locations that contain 4 transects. This data collection starts around V11 growth stage and continues once a week through R6. Typically, reflectance is used to help determine the health of a crop by measuring reflectance levels that are not visible with the human eye. Often, depending on the vegetation indices being used, one can determine the amount of plant vigor, the amount of photosynthesis happening and overall health of the crop. When taking measurements, a combination of red, red edge, near infrared, green, and blue wavelengths are being measured simultaneously. By collecting these wavelengths all at once, we can calculate many indices such as NDVI, NDRE, gNDVI, bNDVI plus many others.
To listen to Tyler describe his project, how canopy reflectance is collected, and some first year results catch this video on Corn Edge Effect Research.