Impact of simulated drought and cover crop mixtures on subsequent spring wheat yield

Cover crops (CCs) are promoted as a mechanism for reducing soil erosion, enhancing soil fertility, and improving diversity in agricultural systems, but in drier climates, there are concerns about their impact on soil water availability for the subsequent crop. We conducted two trials to evaluate the impact of CC mixtures on subsequent spring wheat ( Triticum aestivum L., SpW), irrigated at either 75% or 100% of the long‐term average precipitation. In the first year of each trial, plots were seeded with one of two full‐season CC mixtures or SpW. The CC treatments included GL, a grass‐legume mixture composed of spring triticale (X Triticosecale Wittmack ‘VNS’) and forage pea ( Pisium sativum ‘Arvika’ L.), and GGLF, a mixture of two grasses, triticale and white proso millet ( Panicum miliaceum L. ‘VNS’), a legume (forage pea), and a forb, forage radish ( Raphanus sativus L. ‘Nitro’). In the second year of each trial all plots were seeded to SpW, with half irrigated at the 75% rate and half irrigated at the 100% rate. Previous CCs and irrigation treatments impacted SpW yields only in Trial 1 (2015–2016) but not in Trial 2 (2018–2019). In Trial 1, plots previously planted with a GL produced less grain and residue than the other treatments under 75% irrigation but more grain and residue with the 100% irrigation rate. Yields and residue were not influenced by irrigation treatments in plots previously planted with SpW or GGLF. Despite no treatment effects in Trial 2, SpW produced higher grain yields but less residue than Trial 1. Our experiments suggest that the influence of a previous season's CC on SpW may be overshadowed by management decisions or current growing conditions but also indicate wheat yields are not systematically improved or diminished by a single preceding CC.