How to Prepare a Master Calibration Sample: Procedure and Applications Using Tall Fescue as a Model

Standard calibration samples are used in the uniform blowing procedure to calibrate General-type seed blowers to even out the physical variation among them and achieve uniformity in separating lightweight inert matter from pure seed. Currently, there is no standardized procedure for production of calibra tion samples for tall fescue (Festuca arundinacea Schreb.), one of the main cool season forage crops in the U.S. The objective of this study was to develop a stepwise procedure to prepare standard calibration samples for tall fescue (TF) with proven uniformity, i.e., master calibration samples (MCS). The optimum blowing point (OBP) for tall fescue was identified. It was defined as the point at which almost all lightweight inert matter was removed via blowing (light fraction) and the pure seed remained in the heavy fraction. Various tall fes cue samples representing different varieties, production years, and growing conditions were used to produce the light and heavy fractions of nine mas ter calibration samples. Uniformity of the MCS developed in this study was tested. The MCS identified the OBP across several blowers, and, samples with different levels of inert matter were uniformly separated. The prescribed procedures can be used as a guideline to prepare master calibration samples for other species because the principles of preparation are the same.