Kochia Suppression with Cover Crops in Southwestern Kansas

Abstract

Kochia (Kochia scoparia L.) is a well‐adapted weed found throughout the semiarid Great Plains and has increased in concern because biotypes with resistance to numerous herbicide modes of action are present, thus reducing options for control. The objectives of the research were to determine if cover crops growing during the fallow phase of a no‐till winter wheat (Triticum aestivum L.)–fallow cropping system could reduce kochia density and biomass without reducing subsequent winter wheat yields. Five fall‐sown cover crops of Austrian winter pea (Pisum sativum ssp. arvense), hairy vetch (Vicia villosa Roth.), winter triticale (Triticale hexaploide Lart.), and mixtures of Austrian winter pea‐winter triticale and hairy vetch‐winter triticale were evaluated and compared with chemical fallow and to five spring‐sown cover crops of spring lentil (Lens culinaris Medik.), spring pea (Pisum sativum L.), spring triticale, and mixtures of spring lentil‐spring triticale and spring pea‐spring triticale. Fall‐sown triticale alone or in mixture reduced kochia density by 78 to 94% and reduced kochia biomass by 98% compared with kochia in chemical fallow. Spring‐sown cover crops and kochia emerged together in early March; thus kochia density and biomass were not affected by these cover crops. Fall‐sown cover crops that produced more biomass were most effective at suppressing kochia density and biomass. All cover crops were terminated by either forage harvest or chemical application by June 1. Subsequent winter wheat yields varied by cover crop across years, and in general winter wheat after cover crops yielded comparable to or less than chemical fallow.