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Remote Sensing

By-Plant Prediction of Corn Forage Biomass and Nitrogen Uptake at Various Growth Stages Using Remote Sensing and Plant Height

^a Monsanto Co., 41006 Old Leland Rd., Leland, MS 38756
^b Dep. of Plant and Soil Sciences, 368 Agricultural Hall, Oklahoma State Univ., Stillwater, OK, 74078
^c Ohio State Univ., OARDC-SENR, 1680 Madison Ave., Wooster, OH 44691
^d Dep. of Agronomy, 2308 Throckmorton Plant Sciences Center, Kansas State Univ., Manhattan, KS 66506
^e Dep. of Crop and Soil Sciences, 123 Horticultural Bldg., Univ. of Georgia, Tifton, GA 31793

^* Corresponding author (bill.raun{at}okstate.edu)

Received for publication April 27, 2006. As research intensifies on developing precision agricultural practices for corn (Zea mays L.) production, an important component will be to identify the scale at which these practices should be implemented. We hypothesized that optical sensing can be used to measure individual corn plant biomass and N uptake. A 3-yr study was conducted at three locations in Oklahoma. Optical sensor readings of normalized difference vegetation index (NDVI) and plant height measurements were collected on individual corn plants at various growth stages ranging from V8 (collar of eighth leaf unfolded) to VT (last branch of the tassel is completely visible) and correlated with individual plant biomass, forage yield per unit area occupied by the plant, and N uptake of that plant. Individual plant height measurement, collected before reproductive growth, was a good predictor of plant biomass across the six site years of the study (r² = 0.81). The index of NDVI x plant height provided the highest correlation with by-plant forage yield on an area basis. Optical sensor and plant height measurements collected at the V8 to V10 (collar of 10th leaf unfolded) growth stage can distinguish individual plants and provide information as to their biomass accumulation and N uptake. This research demonstrates that by-plant information can be collected and used to direct high resolution N applications. The index, NDVI x plant height, may be used to refine midseason fertilizer N rates based on expected N removal and by-plant measurements at or before V10.

Abbreviations: FWHM, full width half magnitude • GDD, growing degree days • LCB, Lake Carl Blackwell • NDVI, normalized difference vegetation index • NIR, near infrared • PSV, plant spacing variability