Predicting nitrogen fertilizer requirements for corn by chlorophyll meter under different N availability conditions

Rashid, M. T., Voroney, P. and Parkin, G. 2005. Predicting nitrogen fertilizer requirements for corn by chlorophyll meter under different N availability conditions. Can. J. Soil Sci. 85: 149–159. Nitrogen management strategies that enhance fertilizer use efficiency and maximize profitability in corn require a rapid and accurate method to determine the crop N needs of current hybrids. The objective of this study was to evaluate the potential of a portable chlorophyll meter for predicting N fertilizer requirements for corn grown under varying levels of N availability. Several crop management treatments were imposed in an attempt to create conditions ranging from low N availability (oily food waste application in spring and fall, application at different rates in spring) to high N availability (continuous fertilized corn, winter wheat cover crop). Different corn hybrids were sown at different sites (21 site yr) and varying N fertilizer application rates were applied. Chlorophyll meter readings (CMR) were taken at the 5th to 6th leaf stage (V6) using a SPAD-502 chlorophyll meter. The crop management treatments, corn hybrids and their interaction significantly affected the chlorophyll meter readings. A high inverse correlation between chlorophyll meter readings and maximum economic rate of nitrogen (MERN) was observed (r = –0.87). The main new and unique aspect of our research is the development of a linear model for using chlorophyll meter measurements to make N fertilizer recommendations (MERN = 348.47 – 8.5304 × CMR) for corn production under varying degrees of N availability in Southern Ontario.