Comparison of three methodologies for efficient seed extraction in studies of soil weed seedbanks

Abstract

Determination of weed seeds in the soil is tedious and time consuming. To evaluate the different seed extraction methods to improve seedbank estimations, three extraction methods (sieving, cloth bag and flotation) were compared, based on their accuracy and time needed for separation processes and enumeration. Seeds of Datura stramonium, Amaranthus retroflexus, Portulaca oleracea and Plantago major were used to artificially infest soil samples of four textures, namely clay, clay loam, loam and sandy loam containing 19%, 27%, 38% and 65.5% sand respectively. Soil textures had a significant effect on counting time in all extraction methods. In flotation, four submethods involving different solutions and centrifuge rotation speed were examined, but showed no differences, so data were pooled. Counting time in flotation, cloth bag and sieving methods was 9, 16 and 30 min respectively. However, when the time needed for other processes was taken into consideration, flotation and bag methods did not differ significantly. Species-wise seed recovery was not affected by soil texture in the bag method, suggesting an advantage for this approach as its accuracy is not soil texture-dependent. Total seed recovery for flotation, sieving and bag methods was 61%, 67% and 75%, respectively, and was not significantly different. Considering the efficiency of methods, the cloth bag technique could be recommended, because it was as time consuming as the flotation method, but required the same minimum equipments and costs as the sieving method. © 2007 The Authors.