Graduate Thesis Or Dissertation


Annual Forages Differ in Response to Partial-Season Irrigation Deficit in Both Spring Seeded and Summer Seeded Cropping Systems Public Deposited

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  • Water scarcity during summer becomes a serious problem in the Pacific Northwest, threatening forage production provided to livestock. Annual forages show great potential in handling drought because of their flexibility in seeding date and short growing season, and can shift the production to periods of feed shortage and fill the forage gap. This project focused on determining the annual forage species best suited to different irrigation regimes in both spring and summer seeded cropping systems. The study was conducted for two years and determined the yield, quality, water use efficiency (WUE)and phenology of twenty annual forages under full season irrigation (W1), early season cutoff (W2), late season cutoff (W3), and no irrigation (W4) at Union, OR, on a La Grande silt loam (fine-silty, mixed, superactive, mesic Pachic Haploxeroll). Results showed that DM yield decreased while forage quality increased (higher CP%, lower ADF% and NDF%) when water stress occurred. W2, rather than W1, could be applied to allow good production and better quality and conserve water as well. In addition, summer seeding of annual forage as a cover crop after winter triticale is not recommended in a Mediterranean climate with inadequate irrigation water (W3 and W4). Annual warm season grasses (AC4) generally had the highest yield while annual legumes (AL) had the best quality. In a spring seeded cropping system, there was a 2.6-fold range in forage yield between species under W1, a 2.4-fold range under W2, a 4.1-fold range under W3 and a 5.0-fold range. Within AC3, a 1.5-fold, 1.6-fold, 1.6-fold and 3.2-fold range existed between forage under W1, W2, W3 and W4, respectively. Within AL, the yield range was 1.5, 2.2, 4.3 and 4.6 fold between forages under W1, W2, W3 and W4, respectively. Radish (Raphanus sativus L. var.longipinnatus) outyielded others (10.9 Mg/ha on average) irrespective of irrigation treatments within annual brassica (AB). In a summer seeded cropping system, oat (Avena sativa L.) had the highest production (6.7, 5.2 and 1.8 for W1, W2 and W3, respectively) under irrigation. Within AL, no difference existed among species across irrigation. Radish (Raphanus sativus L. var.longipinnatus) (5.9 Mg/ha) outyielded other brassicas irrespective of irrigation treatments within AB. Sorghum-sudan [Sorghum bicolor (L.) Moench] had the highest production across irrigation treatments in both 2017 (6.0 Mg/ha) and 2018 (10.2 Mg/ha). On average, teff [Eragrostis tef (Zuccagni) Trotter] (14.7% for spring seeded; 10.5% for summer seeded), annual ryegrass [Lolium multiflorum L.] (14.1% for spring seeded; 16.2% for summer seeded) and chickling vetch [Lathyrus sativus L.] (20.8% for spring seeded; 19.7% for summer seeded) had the highest CP% within AC4, AC3 and AL, respectively. In summary, annual forages have potential to augment the perennial forage shortage in the PNW with flexible planting dates and short growing seasons and matching species selection and/or cropping systems with available water will give annual forages more opportunity.
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Peer Reviewed
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  • Ongoing Research
Embargo date range
  • 2019-06-04 to 2020-01-04



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