Evaluation of grain moisture measurement methods suited for developing countries

Abstract

Cost-effective measurement methods that are feasible for smallholder farmers in developing countries are needed for monitoring stored grain quality. The objectives of this study were to: 1) evaluate six commercially available grain moisture indicators for accuracy and precision, 2) indicate advantages and limitations of each device, and 3) assess the suitability of each method for use in developing countries. Whole kernels of shelled corn, soft red winter wheat, and paddy rice were prepared at various moisture content (MC) levels and measurements followed manufacturer's instructions. Replicated measurements were taken with each method (KSU-GT200, John Deere SW08120, Agratronix MT-16, Dickey-john M3G, Hygrometer, DryCard) at each MC and grain combination. Procedures ensured uniform mixing of each sample. As a reference, MC was determined using a standard oven method. For the DryCard (cards coated with a chemical that reacts to humidity) and hygrometer methods, repeatability was indicated using additional grain samples that were near the critical relative humidity specified by the manufacturer (65% RH). At 14.5%wb moisture content, the John Deere SW08120 measured moisture content of corn with the highest precision. Minimum and maximum differences (%wb MC) from oven results for all grains were 0.1% (KSU-GT200) and 3.7% (Dickey-john M3G), respectively. Measurements for paddy rice at higher MC levels (above 15%wb) were highly accurate (0.1%).