Submitted to: Communication in Plant and Soil Analysis
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/18/2011
Publication Date: 5/22/2012
Citation: Yang, Y., Timlin, D.J., Fleisher, D.H., Lokhande, S., Chun, J.A., Soo-Hyung, K., Staver, K., Reddy, V. 2012. Nitrogen concentration and dry matter accumulation in maize crop: Assessing maize nitrogen status with an allometric function and a chlorophyll meter. Communication in Plant and Soil Analysis. 43(11):1563-1575. Interpretive Summary: It is important to apply enough nitrogen to corn at levels high enough to maintain optimum growth, but not too high to result in excess nitrogen that can move to ground or surface waters. Growers and researchers often utilize instruments that can determine nitrogen status by monitoring the color in leaves of the corn plant. This instrument requires additional information to be collected or information from high nitrogen plots to reduce the variability of the measurements. We have developed a method that reduces this variation and enables growers and researchers to determine relative nitrogen status over the growth cycle of the crop. This information is of interest to agricultural managers and researchers interested in quantifying the nitrogen status of a corn crop through the season.
Technical Abstract: The ability to determine the minimum critical nitrogen (N) content in maize plants in order to obtain maximum growth is important to the management of the crop. To conduct plant-based N nutrition diagnosis in maize, it is essential to establish a critical N concentration ([N]), which is the minimum nitrogen concentration necessary to achieve maximum growth. Several authors have shown that [N] declines as a function of aerial biomass accumulation (W): [N] = 3.4W raised to the power of -0.37. This [N] – W relationship has been shown to be a promising diagnostic tool of nitrogen status in maize. However, when applying this [N]-W relationship in maize nitrogen status diagnosis, knowledge on both biomass and nitrogen concentration of the whole aerial part are needed, making the diagnosis process both labor intensive and time consuming. The goal of this study is to evaluate the applicability of relating chlorophyll meter readings with the critical [N] to provide a tool for whole plant nitrogen status diagnosis in maize. Biomass of shoot and specific organs, nitrogen concentration, as well as chlorophyll meter measurement of specific leaves, were determined bi-weekly during the growing season in 2007 and 2008. Another set of data collected in 2005 was also used in validating the relationship between chlorophyll meter measurement and leaf nitrogen concentration. The measured [N] of the whole plant followed the trend described by the [N]-W relationship well. Nitrogen concentration measured from different organs indicated that whole plant nitrogen status can be represented by the nitrogen concentration of the top most fully expanded leaf. A quantitative relationship between nitrogen concentration and chlorophyll meter measurement on the upper most expanded leaf was established and validated. The established relationship between chlorophyll measurement and leaf nitrogen concentration strengthened the applicability of the critical [N] - W relationship in the diagnosis of maize nitrogen status.