Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/20/2010
Publication Date: 7/19/2010
Citation: Sheridan, A.H., Kitchen, N.R., Sudduth, K.A. 2010. Canopy Reflectance Sensing as Impacted by Corn Hybrid Growth. In: 10th International Conference on Precision Agriculture, July 18-21, Denver, Colorado. Available: http://www.icpaonline.org/finalpdf/abstract_213.pdf.
Interpretive Summary: Growing concerns for the health of the environment and climate change have made farmers and the public increasingly interested in technologies that help use agricultural chemicals more efficiently. For example, fertilizer application is vital for most crop production, and questions remain about how much fertilizer is needed to meet crop needs without over-applying. Nitrogen (N) is usually the most important fertilizer nutrient to apply in corn production, and is an environmental concern. A relatively new way to guide N application in corn is through the use of reflectance sensors mounted on the front of fertilizer applicators. Typically, the light reflected from a small area of corn that has been well-fertilized with N is compared to areas of corn that have not yet been fertilized, and the difference between these two is used determine how much N to apply. The purpose of this research was to compare reflectance sensor readings from a number of corn hybrids produced by different companies, to see if hybrid differences were measurable with these sensors. We were also interested in the possible effect of soil color differences on sensor measurements. Differences between hybrids were greatest for corn less than 2 feet in height. Soil type and how wet the soil surface was the day of sensing had more effect on sensor readings than did hybrid. The results of this study are useful because they provide reasonable sensor ranges for well-fertilized corn. These values could be used in software controlling N fertilization. Farmers may benefit from this research because it can help improve the accuracy of N fertilizer application to crop fields. When excess N applications are reduced, fertilizer costs for the farmer go down. Likewise N loss to lakes and streams could be reduced, thereby helping protect the environment.
Technical Abstract: Detection of physical and chemical properties with canopy reflectance sensing could help predict the overall health and yield of a corn crop. Little research has been done to show differences of corn hybrids on canopy reflectance sensing. This study was conducted to examine potential hybrid differences during the early- to mid-vegetative growth stages of corn on three different soil types in Missouri. Canopy sensing (Crop Circle) and SPAD chlorophyll meter readings were taken through most growth stages from V3 to V10 on 11 (2008 growing season) and 8 (2009 growing season) hybrids. Variability within and between hybrids was most noted for corn less than 60 cm in height. Results showed that soil type (site) and soil surface wetness impacted canopy readings more than hybrid. The results of this study could prove useful in determining reasonable ranges for N-rich reflectance values in variable rate N applications.