Estimation of Mass Ratio of the Total Kernels within a Sample of In-Shell Peanuts Using RF Impedance Method

It would be useful to know the total kernel mass within a given mass of peanuts (mass ratio) while the peanuts are bought or being processed. In this work, the possibility of finding the mass ratio while the peanuts were in their shells was investigated. Capacitance, phase angle, and dissipation factor measurements on a parallel-plate capacitor holding in-shell peanut samples were made at frequencies from 1 to 10 MHz insteps of 1 MHz. A calibration equation was developed by multilinear regression analysis correlating the percentage ratio of the kernel weight with the measured capacitance, dissipation factor, and phase angle values of in-shell peanut samples with known kernel weights. The equation was used to predict the percentage mass ratio in the validation groups. Fitness of calibration model was verified using standard error of calibration, root mean square error of calibration, and leverage and influence plots. The predictability percentage, within 1% and 2% of the visual determination, was calculated by comparing the kernel mass ratio, obtained by the model equation and the reference value obtained by visual determination. Cross-validation gave 96% and 100% predictability, and external validation gave 87% and 98% predictability within 1% and 2% difference, respectively.

Time of Removal of Crownbeard (Verbesina encelioides) on Peanut Yield

Field experiments were conducted in southwestern Oklahoma near Colony in 2000 and near Ft. Cobb in 2001 to quantify the effect of time of removal of a natural population of crownbeard on peanut yield. Weed densities and dry weed weights were measured at eight weed-removal times, and in-shell peanut yields were determined at harvest. Crownbeard was removed at 0 (the weed-free check), 4, 6, 8, 10, 12, 14, and 16 wk (full season) after crop emergence (WAE). Weed density was a poor predictor for dry weed weight and peanut yield; however, dry weed weight and time of removal were good predictors for peanut yield. Weed growth was minimal up to 4 WAE and increased linearly after that time. For each week of weed growth, a 0.52 kg/plot increase in dry weed weight was measured. Peanut yield decreased linearly because of crownbeard competition. For each kilogram per plot increase in dry weed weight, a 129 kg/ha or 5.1% peanut yield reduction took place. For each week of weed interference, a 75 kg/ha or 2.8% peanut yield reduction occurred. Crownbeard removal by or before 4 WAE will minimize losses in peanut yield because of interference.