SPATIAL RELATIONSHIPS BETWEEN SEEDBANK AND SEEDLING POPULATIONS OF COMMON LAMBSQUARTERS (CHENOPODIUM-ALBUM) AND ANNUAL GRASSES

Predictions of weed seedling populations from seedbank data should cha racterize the spatial distribution as well as the composition and abun dance of weeds, The spatial distribution of seedbank and seedling popu lations of common lambsquarters and annual grasses (giant foxtail, lar ge crabgrass, and fall panicum) were described in moldboard plow and n o-tillage soybean fields from 1990 to 1993, Spearman rank correlations between seedbank and seedling densities were significant for common l ambsquarters in both. tillages and all years, but for annual grasses c orrelations were significant only in no-tillage. Semivariograms showed spatial autocorrelation in seedbank and seedling populations of commo n lambsquarters in all years in no-till, but less often in the moldboa rd plow field, Annual grass seed and seedling populations were autocor related in the no-till field every year except 1993, and in the moldbo ard plow field in 1992 and 1993 only, Cross-semivariograms showed spat ial continuity between seedbank and seedling population densities in 3 of 4 yr in no-till for common lambsquarters, and in all years of no-t ill and 1 yr of moldboard plow for annual grasses, Grey-scale field ma ps of common lambsquarters seedbanks corresponded visually to maps of seedling populations and could have been used to target control effort s, but visual correspondence between annual grass seedbank and seedlin g maps was poor, Seedbank and seedling mapping may be useful for site- specific management, but additional information is needed to understan d the variation in the relationships between these two populations ove r time and space.