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1999 STEEP III Progress ReportRESEARCH PROJECT TITLE: Integrated Management System for Sustained Seed Yield of Kentucky Bluegrass Without Burning INVESTIGATORS: Donn Thill and Glen Murray, Univ. of Idaho, and Bill Johnston, Wash. State Univ OBJECTIVES:
KEY WORDS: Roundup (glyphosate), chemical suppression, intercrop STATEMENT OF PROBLEM: Non-thermal bluegrass
seed production systems will reduce the consecutive number of bluegrass
seed crops from ten or more to about two. More frequent bluegrass establishment,
increased potential for soil erosion, and increased annual weeds further
decrease economic opportunities for sustained bluegrass seed production.
High stand density may be partially responsible for seed yield decline,
especially when post-harvest residue is removed mechanically. Stand suppression
and thinning with spring applied Roundup may restore seed yield. No-till
planting of annual crops in Roundup suppressed bluegrass stands may allow
economic return during renovation. ZONE OF INTEREST: Palouse and Camas Prairie regions of Washington and Idaho ABSTRACT OF RESEARCH FINDINGS: Following harvest
in 1998, trials were established in fields of 'Rhonde', and 'Kenblue'
Kentucky bluegrass near Fairfield, WA, and in fields of 'Nublue' and 'Palouse'
near Nezperce, ID, to determine whether stand suppression and thinning
with Roundup can sustain bluegrass production cycles in high and low residue
areas, and to determine whether an intercrop of lentil, pea, or oat, seeded
into the suppressed sod would benefit this management system. Prior to
spring Roundup application, bluegrass tiller density gradually increased,
reaching a maximum 3 to 4 weeks prior to planting, which ranged from 424
to 877 tillers/ft2 at the driest and wettest sites, respectively. After
spraying Roundup, tiller density was 27 and 51% less in low compared to
high residue treatments in 'Kenblue' and 'Nublue' fields, respectively.
Tiller densities in recovering stands of bluegrass were lowest in early
flowering varieties, and averaged 7, 13, 20, and 51% of control plot densities
in 'Palouse', 'Kenblue', 'Rhonde', and 'Nublue', respectively. Percent
bluegrass tiller recovery usually was similar between low and high residue
treatments for all varieties except 'Nublue'. Later applications of Roundup
usually resulted in the lower bluegrass tiller recovery. Roundup applied
at 1.0 lb ai/A two weeks prior to planting intercrops suppressed bluegrass
equal to or more than all other treatments. Intercrop stand density and
seed yield in low residue treatments were greater than or equal to the
high residue treatments, and were negatively correlated with Kentucky
bluegrass recovery. Density of bluegrass C-tillers was reduced over winter
in all varieties. Bluegrass panicle densities and seed yields were lowest
in plots with low C-tiller densities. RESULTS AND INTERPRETATION: Following bluegrass seed harvest in 1998, trials were established at two locations representing four different common and proprietary varieties (Table 1). The sites near Fairfield, WA are in 'Rhonde' and 'Kenblue' fields, and near Nezperce, ID in 'Palouse' and 'Nublue' fields. Each site contains two experiments replicated four times: an intercrop experiment (experiment 1) and a herbicide experiment (experiment 2). Main plots are high and low post-harvest residue treatments and subplots are intercrops or herbicide treatments. During late August through early September, 1998, the low residue treatments were mowed, raked, and baled at the Fairfield site, and were burned at the Nezperce site, while high residue treatments at Fairfield and Nezperce were re-swathed and baled without raking. Sod cores (4-inch dia.) were collected during October and November, 1998, to determine the number of C-tillers. In experiment one, Roundup was applied at 1 lb ai/A across both residue treatments two weeks prior to no-till planting 'Phantom' leafless pea, 'Monida' oat, and 'Pardina' small brown lentil. In experiment two, eight Roundup treatments were applied across both residue treatments: 1 lb ai/A applied at 6, 5, 4, 3, and 2 weeks prior to planting the lentil, 1.5 lb ai/A applied 2 weeks preplant, and split applications of 1.0 + 1.0 lb ai/A and 0.75 + 0.75 lb ai/A applied 6 and 2 weeks before planting. Liquid AMS at 17 lb/100 gal mix was added to all Roundup treatments. The Fairfield sites were seeded using a Great Plains no-till drill with 7 inch spaced rows. The Nezperce sites were seeded using a John Deere model 750 no-till drill with 7.5-inch spaced rows. Lentil, pea, and oat were seeded at 52, 190, and 90 lb/A, respectively. All crops received 40 and 20 lb/A of P and S, respectively. Oats also received 100 lb/A N. Both experiments included non-renovated bluegrass control plots (no Roundup or intercrop) that were fertilized during fall 1998 as per the remainder of the field. During spring 1999, sod cores were taken from each plot in both experiments one week prior to spraying and two weeks after seeding the intercrops. Tiller number and type, and rhizome weight were determined. Bluegrass recovery was evaluated visually after seeding the intercrops. Crop stand counts were determined in all the intercrop experiments. Weeds and insects were monitored and controlled as needed. Panincles were counted and seed was harvested in the non-renovated bluegrass plots as well as the intercrop plots at maturity. Bluegrass hundred seed weight, and 7 and 28 day germination is being determined. Following harvest in 1999, post harvest residue was removed from the bluegrass control plots using the same methods as in 1998. Fertilizer was applied to the plot areas in October, 1999, at the same time and rate as the remainder of the bluegrass field, except in the nitrogen timing treatments. In control and lentil intercrop plots of 'Nublue' and 'Palouse', fall fertilizer was applied at 100, 70, and 30% of field rate in preparation for split spring applications of 0, 30, and 70% field rate, respectively. Density of fall tillers, which had initiated prior to harvest in 1998, (C-tillers) were determined in November 1998, and March 1999, and will continue in November 1999, and March 2000. Objective 1: Prior to spraying Roundup, average bluegrass tiller density ranged from 424 (driest site) to 877 (wettest site) tillers/ft2 among sites, but was uniform within a site (Table 2). Residue removal treatment did not affect the number of tillers when counted in the spring prior to spraying Roundup. However, after spraying Roundup, bluegrass tiller number was 27 and 51% less in low compared to high residue treatments in 'Kenblue' and 'Nublue' fields, respectively. Average post Roundup recovery of bluegrass tiller number was 7, 13, 20 and 51% for 'Palouse' (early flowering variety), 'Kenblue', 'Rhonde', and 'Nublue' (late flowering variety), respectively and was not affected by intercrop. Intercrop stand density and seed yield in low residue treatments was greater than or equal to the high residue treatments. Objective 2:
Pre-Roundup tiller densities usually increased with later sampling, generally
reaching a maximum at 3 to 4 weeks prior to planting (Table 3). The total
number of bluegrass tillers following Roundup application was not affected
by residue treatment except in the variety 'Palouse' where density was
77% less in low versus high residue treatments. Percent visual recovery
ranged from 15 to 19% for 'Rhonde', 'Kenblue' and 'Palouse', and was 49%
for 'Nublue'. Bluegrass tiller recovery was best in high residue treatments
for 'Palouse' and 'Nublue' (the low residue treatments were burned during
fall 1998). Later applications of Roundup usually resulted in the least
tiller recovery. Roundup applied at 1.0 lb ai/A, 2 weeks prior to planting
intercrops suppressed bluegrass equal to or more than all other treatments.
Lentil stand averaged about 11 plants/ft2, and was significantly reduced
by high residue in the variety 'Nublue'. Lentil seed yield was greatest
in plots with the least Kentucky bluegrass recovery. Lentil seed yield
was negatively correlated with both visual recovery and post-glyphosate
tiller density in all varieties (Table 4). Lentil yields in low residue
treatments were greater than or equal to high residue treatments. Fall
C-tiller density of bluegrass in high residue treatments was greater than
or equal to densities in low residue treatments in all varieties (Table
5). By spring 1999, the number of persisting C-tillers was severely reduced,
especially in high residue treatments. Panicle densities were lowest in
plots with low C-tiller densities. Seed yield was greatest in treatments
with high panicle density. INTERACTION WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: Fairfield plots were shown to the Spokane County Crop Improvement Association on June 15, 1999. The Nezperce plots were included in the Lewis County field tour on July 5, 1999. PUBLICATIONS AND PRESENTATIONS: Thill, D.C., G.A. Murray, and W.C. Johnston. 1999 Integrated Management System for Sustained Seed Yield of Kentucky Bluegrass Without Burning. GSCSSA Annual Report. Murray, G.A., D.C. Thill, J.B. Swensen, and J. Reed. 1998. Integrated management system for sustained seed yield of Kentucky bluegrass without open-field burning. Western Soc. Crop Sci. ASA Abstracts, appendix 3, p.4. Fairfield plots were shown to the Spokane County Crop Improvement Association on June 15, 1999. The Nezperce plots were included in the Lewis County field tour on July 5, 1999.
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