Spatially variable patterns of wild oat emergence in eastern Washington

Wild oat is one of the most economically important and widely distributed weed species in eastern Washington. The timing of wild oat control in this region is affected by the extreme topographical diversity. The objective of this research was to assess the influence of landscape diversity on the pattern of wild oat emergence. Wild oat emergence was monitored at five landscape positions along a north/south transect. The timing of emergence across the landscape tended to follow the distribution of solar radiation, such that wild oats emerged earlier at landscape positions with greater solar radiation and thus, higher soil temperatures. The time to reach 25% of maximum emergence was reached on average 17 days earlier at south- compared to north-facing landscape positions. This difference was maintained over the course of the emergence period. These results show that site properties, such as slope, aspect, and elevation, affect the thermal and hydric conditions in the soil seed bank and can cause site-specific patterns of wild oat emergence.