Spring Establishment of Orchardgrass Seed Crops with Cereal Companion Crops

Orchardgrass (Dactylis glomerata L.) does not produce a seed crop during the first growing season. Income produced by establishing orchardgrass seed crops with cereal companion crops could offset revenue lost when a seed field is planted. This investigation was conducted to ascertain the feasibility of establishing orchardgrass seed crops with spring cereals and examine the biological and economic responses of orchardgrass to competition with cereals. ‘Hallmark’ orchardgrass was interplanted with ‘Waverly’ spring wheat (Triticum aestivum L.), ‘Steptoe’ spring barley (Hordeum vulgare L.), and ‘Cayuse’ spring oats [Avenafatua var. sativa (L.) Haussk.] in 15- and 30-cm rows at right angles to grass rows. Cereals shaded orchardgrass seedlings, resulting in transitory increases in chlorophyll content. Cereals reduced soil moisture content, causing water stress in orchardgrass seedlings as indicated by greater stomatal resistance and lower transpiration rate, which reduced urchardgrass tiller and dry matter production. The negative effects on growth persisted into fall and winter, reducing fertile tiller production during the following spring. Consequently, spring cereals reduced firstyear seed yields by 40% in Trial 1 and 53% in Trial 2. Seedling growth and first-year seed yields were similarly reduced by all cereals and row spacings. Second-year seed yield was not influenced by cereals. Net income was increased by $212 ha⁻¹ over a 3-yr period in Trial 1 with wheat in 30-cm rows. However, drier conditions in Trial 2 caused low cereal and orchurdgrass seed yield, making establishment with cereals unprofitable. This study demonstrated possible negativeffects of spring cereals on orchardgrass stand establishment; nevertheless the potential for increased profitability of orchardgrass seed crops planted with wheat companion crops was shown. Contribution of the Oregon Agric. Exp. Stn., Corvallis. Technical Paper no. 8488.