Judit Barroso

1 Introduction Weeds adapt in response to intensive farming practices (Neve and Caicedo 2022). Over the past two centuries, agricultural practices have rapidly intensified across North America through cropland expansion, monoculture systems and increased chemical inputs (Kreiner, Caballero et al. 2022). Chemical weed control revolutionised weed management by enhancing the levels of weed control while reducing labour input and costs (Swinton and Van Deynze 2017).

CC cover crop GDD growing degree days GWC gravimetric water content PNW Pacific Northwest VWC volumetric water content 1 INTRODUCTION The typical cropping system for winter wheat (Triticum aestivum L.) production in semiarid areas of the dryland Pacific Northwest (PNW) is a wheat–fallow rotation. These areas have a Mediterranean climate, characterized by hot and dry summers.

Lolium multiflorum Lam. (Italian ryegrass, annual ryegrass) is both a weed and a crop in Oregon. Because it is commonly managed using chemical controls, herbicide-resistant populations have evolved within the seed production region. A glyphosate-resistant population was identified in Yamhill County, Oregon, in a fallow field previously cropped with perennial ryegrass.