Irrigation applied at a rate of 3.0 inches per month (0.75 inches per week) from July to September will provide improved perennial ryegrass turf quality and percent green cover in western Oregon.• Replacing 45 to 49% evapotranspiration is adequate to maintain acceptable turfgrass quality in this environmental zone.• Three inches of irrigation per month (0.75 inches per week) will provided perennial ryegrass turf quality and percent green cover equivalent to great irrigation amounts.• Eight irrigation applications per month (twice a week) will result in acceptable perennial ryegrass turf quality during the summer months while 16 applications per month (four time a week) will provide the greatest perennial ryegrass turf quality.Oregon State Univ., 4147 ALS Building, Corvallis, OR. *Corresponding author (alec.kowalewski@oregonstate.edu).
Annual bluegrass (Poa annua L.) encroachment may increase when turfgrass is maintained with excessive irrigation; however, with proper deficit irrigation, annual bluegrass germination and growth may be suppressed while desirable turfgrass is sustained. The goal of this project was to determine the optimal irrigation regime for suppressing annual bluegrass in perennial ryegrass (Lolium perenne L.) stands during the summer months. Two frequencies (once or four times a week) and rates (45% and 80% reference evapotranspiration [ET ref ] replacement) were used to assess the encroachment of annual bluegrass in perennial ryegrass maintained at 5 cm. Experimental design was a 2 × 2 factorial randomized complete block design with four replications. Preliminary findings suggest that irrigation applied once a week will reduce annual bluegrass compared to irrigation four times a week, while ET ref replacement had no effect on annual bluegrass encroachment. Findings also suggest that frequent irrigation will increase turfgrass quality and soil moisture in the top 3.8 cm.
Annual bluegrass (AB; Poa annua L.) infestation is aided by phosphorus (P), but there is no information evaluating the effect of P on AB encroachment into turfgrass at seeded establishment. We hypothesized AB seedling survival and vigor will increase with P rates, compromising establishment of desired turfgrass species.Greenhouse pot studies evaluated the effect of P application rate on AB establishment or cover when seeded with perennial ryegrass (Lolium perenne L.) or creeping bentgrass (Agrostis stolonifera L. '007'). Two experimental runs were repeated in time. In perennial ryegrass, five P rates (0, 25, 50, 100, and 200 kg P ha −1 ) and two cultivars ('Black Cat II' and 'Home Run LS') were tested in sand media (11 mg kg −1 Mehlich-3 extractable P). In creeping bentgrass, five P rates (0, 12.5, 25, 50, and 100 kg P ha −1 ), which were modified in the second run (0, 6.25, 12.5, 25, and 50 kg P ha −1 ), were tested in sand media (3 mg kg −1 Mehlich-3 extractable P). Regardless of cultivar, AB establishment in perennial ryegrass improved when P was applied and was 90% of maximum at 1.7 kg P ha −1 . In creeping bentgrass, both AB and creeping bentgrass cover increased when P was applied and AB was 90% of maximum at 12.1 kg P ha −1 . Creeping bentgrass cover was not compromised by P application rates as low as 6.25 kg ha −1 . Phosphorus enhances AB cover from seed when sown with perennial ryegrass or creeping bentgrass seed in low P soils.
Few projects have explored the long-term effects of N rates on multiple weed populations in the Pacific Northwest. The objectives of this research were to evaluate the effects of N application timing and annual N rates on weed population dynamics in a perennial ryegrass (Lolium perenne L.) stand in western Oregon. Factors in this project included N application timing [spring-heavy (April, May, June, and October), fall-heavy (May, September, October, and November), early spring and late fall (April, June, October, and November), and traditional spring and fall (May, June, September, and October)] and annual N rates (75, 150, and 300 kg N ha −1 annually). An untreated control was also included in this project. The initial findings suggest that after 18 mo without herbicides, the highest annual N rate had the highest annual bluegrass populations but the lowest moss and broadleaf weed populations. The spring-heavy fertilization program at the low annual rate resulted in higher broadleaf weed populations than all other N application timing × N rate combinations. Data will continue to be collected from this experiment to determine the effects of N application timing and annual N rates on weed population dynamics.
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