Germination Responses of Common Chickweed (Stellaria media (L.) Vill.) to Water Potential, Salinity, and pH and Its Association with Forage Wheat Yield and Nutritive Composition

Common chickweed [Stellaria media (L.) Vill.] is a common winter annual weed in forage wheat (Triticum aestivum L.) fields in California. Lack of control of this species by commonly used herbicides has raised concern about its presence in larger numbers and ability to persist and compete with crops causing yield and crop nutritive composition losses. However, very little is known of its germination ecology, competitiveness, and the resulting effect on the yield and quality of forage wheat. Laboratory studies were conducted to develop an understanding of its germination response under a range of simulated osmotic stress, salinity, and pH conditions. Observational studies in grower fields were also conducted to estimate forage wheat yield and some nutritive components (crude protein, acid detergent fiber, neutral detergent fiber, starch, and ash) in infested and un-infested areas of the fields. The laboratory germination studies showed that common chickweed seeds were very sensitive to osmotic stress but had mild-to-moderate tolerance to salinity and preferred neutral pH rather than alkaline or acidic conditions. Germination was reduced by approximately 50% at −0.133 MPa matric water potential as well as in 14.5 dS m−1 electrical conductivity solution. Fresh weight of forage wheat at harvest was 22 to 44% (depending on crop moisture content) lower and dry biomass was approximately 12% lower in the areas infested with common chickweed compared to the areas without any weeds. The crude protein, acid detergent fiber, and neutral detergent fiber levels of common chickweed were 13.6%, 35%, and 46%, respectively, and it did not reduce the measured nutritive composition of forage wheat. In conclusion, we determined the ideal water potential, salinity, and pH conditions for common chickweed germination and that infestations of this species could reduce yield but not the nutritive components of forage wheat measured in this study.