Experimental approach to evaluate the effect of growing conditions on cereal grain size and its relevance for interpreting archaeological cereal grain assemblages

Measurements of archaeological cereal grains has the potential to improve interpretations of archaeobotanical assemblages and to address a broad range of research questions related to agricultural practices in the past. However, understanding the role of the many factors that can influence the morphometrics of cereal grains is of importance to validate the application of morphometrics in archaeobotany. The aim of this study was to investigate the potential effects of growing conditions on cereal grain size using three experimental factors: site-location with different soil types, manure intensity and plant density. A short-term field experiment was conducted at two locations (Alnarp and Holma) in southern Sweden with hulled barley, naked barley, bread wheat, emmer wheat, einkorn, spelt wheat, rye and oat. Our results show that, while all three factors investigated affect grain size, most significant effect was from manuring (p < 0.0001) and site location with different soil types (p < 0.0001), plant density had the weakest effect (p = 0.005), and that cereal species reacted differently to experimental factors. We further use the morphometric dataset to assess the relationship between grain size variation and growing conditions, using the sample range of grain size from different experimental factors. The experimental data obtained sheds light on how growing conditions may affect grain size and the results are discussed in relation to grain size composition in archaeobotanical assemblages.