Estimates of forage mass in pasture obtained by harvesting small plots may be too low because fragments of the harvested herbage are dropped into the stubble and not recovered. Our objective was to evaluate stubble vacuuming as a means of retrieving such material, thereby improving the accuracy of forage mass estimation. Our study was conducted on intensively managed dairy pastures dominated by orchardgrass ( Dactylis glomerata L.) and white clover ( Trifolium repens L.). The stubble was vacuumed following conventional harvesting of small quadrats to a stubble height of 2 cm. Harvested herbage and vacuumed stubble were oven‐dried separately and then ashed to correct for soil contamination. The slope of the regression of total organic matter (OM), which included vacuumed material, on the mass of harvested herbage without vacuuming showed that clippings lost into the stubble in this study amounted to 0.045 Mg/ha OM for each Mg/ha unvacuumed herbage dry weight or 0.286 Mg/ha OM for each Mg/ha unvacuumed herbage OM. Because of the extra cost of the procedure, it is not recommended, except for ecological studies where very accurate estimations of OM distribution are required.