Measuring Corn Dry-Down: Validation and Application of a Non-Destructive Method.

Corn (Zea mays L.) breeding and production in the shorter growing season environments, requires measuring kernel moisture content nondestructively under field conditions to identify genetic traits and agronomic management that result in rapid loss of moisture from maturing kernels (dry down), early maturity, and lower grain drying costs. Reid et al. (2010. Maydica 55: 163-171) developed a nondestructive method, and calibration curve using a moisture meter (MT808— Electrophysics, Dutton, Ontario) to measure total ear (TEM %) and kernel moisture (KM %) in corn. The purpose of the current study was to develop a second calibration data set to validate the meter and calibration curve proposed by Reid et al. (2010) and to evaluate the precision of the meter with gravimetric method across a range of moisture contents. A population of corn ears at different phenological stages, and thus in kernel moisture content was sampled to measure total ear moisture readings (TEMR), TEM %, KM % on each cob in 2015 and 2016. Samples were collected 26, 47 and 61 days after silking and a total of 240 were tested over both years. Slope comparison and pooling of data from the current study and the original study by Reid et al. (2010) were used to develop new calibration curves for both variables. According to this new model, TEM% and KM % can be estimated using the calibration curves TEM% = 1.28*TEMR (r² = 0.78) and KM% = 1.09*TEMR (r² = 0.81), respectively. The difference in measurement of methods was analyzed using the Bland and Altman methods. The moisture meter consistently under and over estimated gravimetric moisture content in the ear and kernels at high and low moisture content, respectively. The meter most accurately measured kernel moisture content between 40 to 45%.