Graduate Thesis Or Dissertation
 

Establishment of grass seed crops with cereal companion crops

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  • In conventional cropping systems in the Willamette Valley, slow establishing grass species, such as Kentucky bluegrass (Poapratensis L.) are planted in the spring and seed is not harvested until the following year. Due to increasing annual production costs, it is necessary to generate a cash return from each field each production year. This can be achieved by establishing the grass seed crop with a cereal companion crop either in fall or spring. The objective of this study was to identify the suitability of establishing grass seed crops with cereal companion crops in the Willamette Valley. To realize this objective, combinations of companion crop species, seeding rates, planting arrangements and grass species were examined for suitability in a companion cropping system. In addition, competitive effects of the companion crop on undersown grasses were studied. Three field experiments were conducted at two locations in the Willamette Valley over a two-year period (1980-1982). Percent light transmittance was measured in companion crop canopies developed under different seeding rates (67.2 and 100.8 kg/ha) and planting arrangements (parallel with and across grass rows) and in different types of companion crops (winter wheat, spring wheat and spring barley). Soil water potential was determined to investigate moisture patterns due to crop competition. Tiller samples were taken from undersown grasses and from these samples the following growth parameters were determined: tiller number, tiller height, leaf weight and leaf area per tiller, Specific Leaf Weight (SLW), and Leaf Area Index (LAI). Companion crop and grass seed yields were determined to obtain information for the economic feasibility of the companion cropping system. Parallel planting of the grass and companion crops gave higher light transmittance values than cross planting. However, no beneficial effects on grass crop growth parameters were detected. Companion crop seeding rates did not result in different percent light transmittance values, or was there an effect on growth parameters of undersown Kentucky bluegrass and orchardgrass (Dactylis glomerata L.). Soil water potential was higher in Kentucky bluegrass plots established with a companion crop at Gervais than in plots established without a companion crop. Tiller number for Kentucky bluegrass was suppressed by the companion crop for the experiment in Gervais. Tiller number and LAI for Kentucky bluegrass and orchardgrass was lower when established with a companion crop in the fall of 1981 at Hyslop Farm. Tiller height, leaf weight and leaf area per tiller of Kentucky bluegrass was higher when established with a wheat companion crop at Gervais. Leaf weight per tiller and SLW of orchardgrass were suppressed by the wheat companion crop at Hyslop Farm. Differential effects on growth parameters due to different companion crops were not detected. Low companion crop yields did not offset a lower subsequent Bristol Kentucky bluegrass seed yield in Gervais. This resulted in a lower mean annual gross return for the bluegrass seed crop when established with a companion crop. Wheat companion crop yields were approximately 10,000 kg/ha and 6,300 kg/ha when planted with Kentucky bluegrass and orchardgrass, respectively, at Hyslop Farm. Grass seed yields were not obtained for this study due to time constraints. Further investigation is needed to study the effect of companion crop planting arrangements on undersown grasses. The necessity of irrigation and nitrogen fertilization immediately after companion crop harvest for companion cropping systems in the Willamette Valley also need to be further investigated.
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