Relationship Between Coefficient of Variation Measured by Spectral Reflectance and Plant Density at Early Growth Stages in Winter Wheat

The use of by-plot coefficient of variation (CV) has not been evaluated in precision agricultural work. This study evaluated the relationship between CVs determined from normalized-difference vegetative index (NDVI) sensor readings, plant population, and sensing direction on NDVI values. Randomly selected plots, measuring 1 m2 (2003) and 3 m2 (2004), were established for this study. Plots in 2004 were divided into three 1 m2 subplots with, 0 and 120 kg ha−1 fall-applied N, and 80 kg ha−1 topdress nitrogen (N). Sensor reading of subplots were taken at Feekes 5 and 7 using the Green Seeker hand-held sensor. Results showed that the relationship between vegetative RI (RINDVI) and harvest RI (RIHarvest) improved with increasing CV values. The prediction of RIHarvest was improved when CV was integrated into the RINDVI calculation. RIHarvest can be better predicted with RINDVI when the CV of spectral radiance measurements is used in the RINDVI equation.