Pedosphere 20(1): 15--22, 2010
ISSN 1002-0160/CN 32-1315/P
©2010 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Temporal patterns in symptoms of nitrogen deficiency as revealed by remote sensing of corn canopy
1 Temple University, CORE Program, 3223 N.Broad Street, Suite 175, Philadelphia, Pennsylvania 19140 (USA)
2 Department of Agronomy, Iowa State University, Ames, Iowa 50011 (USA)
3 Iowa Soybean Association, On-Farm Network, 1255 SW Prairie Trail Parkway, Ankeny, Iowa 50023 (USA)
4 Winfield Solutions, LLC.114 Washington Avenue, Montevideo, Minnesota 56265 (USA)
      To evaluate the temporal patterns of N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with various rates (56, 112, and 168 kg N ha-1), timing (early and late applications) and placement (injected into soil and dribbled on soil surface) of N fertilization in a split-plot design. Relationships between canopy reflectance during the growing season and yield data at the end of growing season were studied for different treatments. Results showed significant variation in both grain yields and canopy reflectance among the three cornfields. The N fertilization made in early June resulted in low canopy reflectance in early July, but the differences disappeared as the season progressed. The effect of N rates on canopy reflectance was not significant in early July but it gradually became detectable in mid-July and thereafter. The fertilizer placement had a significant effect on grain yields only in one field but not on canopy reflectance in all three fields. These observations suggest that the deficiency of N developed under field conditions is a dynamic phenomenon, which adds complexity for accurately defining "N deficiency" and effectively developing management strategies for in-season correction. Remote sensing throughout the season helps collect information about important interactions that have not been given enough attention in the past.
Key Words:  canopy reflectance, fertilizer placement, timing, yield response
Citation: Zhang, J., Blackmer, A. M., Kyveryga, P. M., Glady, M. J. and Blackmer, T. M. 2010. Temporal patterns in symptoms of nitrogen deficiency as revealed by remote sensing of corn canopy. Pedosphere. 20(1): 15-22.
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