Field chlorophyll measurements for evaluation of corn nitrogen status¹

Contribution of the Department of Agronomy and Soils, Alabama Agricultural Experiment Station, Auburn University, Alabama 36849–5412 in cooperation with the National Soil Dynamics Laboratory, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 792, Auburn, Alabama 36831–0792. This research was supported by checkoff funds from the Alabama Farmers Federation Wheat and Feed Grains Committee.

Abstract

An experiment was conducted on Norfolk sandy loam soil (Fine‐loamy, siliceous, thermic Typic Kandiudults) during two years to determine the feasibility of using field chlorophyll measurements for evaluation of corn (Zea mays L.) N status. Nitrogen was applied at rates of 56, 112, 168, 224, 280 and 336 kg ha^‐1 to establish a range of corn chlorophyll levels, tissue N concentrations, and grain yields. At the V10 and midsilk stages of growth, field chlorophyll measurements were taken with a hand‐held chlorophyll meter (SPAD‐502 Chlorophyll Meter, Minolta Camera Co., Ltd., Japan)³ and tissue N was determined. A typical curvilinear grain yield response to N fertilizer was observed both years; maximum agronomic yields were obtained with 227 and 242 kg N ha¹, respectively, in 1990 and 1991. Tissue N concentrations at V10 and midsiik were a good predictor of grain yield. Field chlorophyll measurements were highly correlated with tissue N concentrations at both growth stages during both years of the study. Field chlorophyll measurements had excellent grain yield prediction capabilities, even at V10, which shows promise for utilization of this tool for in‐season N recommendations. However, further calibration of field chlorophyll measurements will be required prior to routine use for corn N recommendation purposes.

Notes

Contribution of the Department of Agronomy and Soils, Alabama Agricultural Experiment Station, Auburn University, Alabama 36849–5412 in cooperation with the National Soil Dynamics Laboratory, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 792, Auburn, Alabama 36831–0792. This research was supported by checkoff funds from the Alabama Farmers Federation Wheat and Feed Grains Committee.

C.W. Wood and K.L. Edmisten are affiliated with the Department of Agronomy and Soils, 202 Funchess Hall, Auburn University, Alabama 36849–5412. D.W. Reeves is associated with the National Soil Dynamics Laboratory, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 792, Auburn, Alabama 36831–0792. R.R. Duffield is Superintendent, Field Crops Unit, E.V. Smith Research Center, P.O. Box 138, Shorter, Alabama 36075.