The objective of the study was to determine the seed spacing uniformity performance of a precision metering unit when vacuum plates with different number of holes were used. In order to meet this objective, the performances of vacuum plates with different number of holes were evaluated in the laboratory conditions by employing sticky belt tests and seed spacing values were measured computerized measurement system (CMS) for the cotton and corn seeds. Quality of feed index, multiple index, miss index as well as coefficient of precision (CP3) were considered as the performance indicators for precision seeding. The forward speed values were as selected as 1.0, 1.5 and 2.0 m s (1) while vacuum plates with hole diameter of 3.5 mm for cotton and 4.5 mm for corn seeds were used. For both, cotton and corn seeds, five different vacuum plates (20, 26, 36, 52, and 72 holes) were considered in the experiments. In the experiments, vacuum pressure was applied at 6.3 kPa. Based on the findings in this work it appears that 1.0 and 1.5 m s (1) of forward speed values were found to provide the highest performance levels for all vacuum plates. However such performance substantially decreased when forward speed increased to 2.0 m s (1). In overall, the highest performance was determined when 26 and 36 holes were used for cotton and corn, respectively. (C) 2014 Elsevier Ltd. All rights reserved.