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2001 STEEP III Progress ReportTITLE: Integrated Management System for Sustained Seed Yield of Kentucky Bluegrass Without Burning. INVESTIGATOR: Donn Thill, Department of Plant, Soil, and Entomological Sciences, University of Idaho, Moscow, ID 83844-2339 INTERIM OR FINAL REPORT: Interim PROJECT 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: In fall 1998, trials were established in fields of 'Rhonde', 'Kenblue', 'Nublue', and 'Palouse' Kentucky bluegrass, to determine whether stand suppression and thinning with Roundup can sustain bluegrass production cycles in high and low residue areas, and to determine if an intercrop of lentil, pea, or oat, seeded into the suppressed sod would benefit this management system. Except for the two earliest application times in 1999, 'Palouse' did not recover from Roundup treatment. In 2001, panicle number at harvest time harvest in 'Rhonde' and 'Nublue' of was 38% less in non-suppressed bluegrass plots compared to plots sprayed in spring 1999 with 1.5 to 2 lb ai/A of Roundup. Burned plots of 'Nublue' and 'Palouse' had 26 to 33% more panicles at harvest than non-burned plots in 2001. Panicle number at harvest of 'Rhonde' was equal in low and high residue plots (mechanically removed) in 2001. In 2001, panicle number at harvest in 'Rhonde' and 'Nublue' was 29 to 52% greater following the 1999 oat and pea intercrops than the continuous bluegrass crop. Panicle number at harvest in 2001 of 'Nublue' and 'Palouse' were not different among nitrogen treatments. RESULTS AND INTERPRETATION: See the 1999 and 2000 STEEP reports for more detailed information from previous years. Following harvest in 1998, trials were established in fields of 'Rhonde', 'Kenblue', 'Nublue', and 'Palouse' Kentucky bluegrass, each with an intercrop experiment and an herbicide experiment, and having high and low post-harvest residue treatments. The low residue treatments were mowed, raked, and baled in the 'Kenblue' and 'Rhonde' fields, and were burned in the 'Nublue' and 'Palouse' fields, while all fields were re-swathed and baled without raking for the high residue treatments. In the intercrop experiment, Roundup was applied at 1 lb ai/A across both residue treatments 2 weeks prior to no-till planting pea, oat, and lentil intercrops. Intercrop planting dates were April 14, 22, 27, and May 6, 1999 for 'Rhonde', 'Kenblue', 'Nublue', and 'Palouse' fields, respectively. In the herbicide experiment, Roundup was applied at 1 lb/A 6, 5, 4, 3, or 2 weeks prior to planting lentil, 1.5 lb/A applied 2 weeks preplant, and split applications of 1.0 + 1.0 lb/A and 0.75 + 0.75 lb/A applied 6 and 2 weeks pre-plant. Both experiments included non-suppressed bluegrass control plots (no Roundup or intercrop). In July 1999, non-suppressed bluegrass plots were swathed. Grass windrows and standing intercrops were harvested to determine seed yield. The 'Kenblue' site was inadvertently plowed up and is no longer part of the study. Following harvest in 1999 and 2000, post harvest residue was removed from the bluegrass plots using the same methods as in fall 1998. In 1999, oat straw was raked from the intercrop plots but pea and lentil straw was allowed to remain. Fertilizer was applied to the plot areas in October 1999 and 2000, at the same time and rate as the remainder of the bluegrass field, except in the nitrogen timing treatments. In Kentucky bluegrass control and lentil intercrop plots of 'Nublue' and 'Palouse', fall fertilizer was applied at 100 (135 lb N/A), 70, and 30% of field rate and followed by spring applications of 0, 30, and 70% field rates, respectively. Spring applications were at early re-growth and early stem elongation. In the fall of 1998 and 1999, 4-inch sod cores were dissected to determine C and F tillers. In the spring of 1999, 2000, and 2001 panicles derived from C and F tillers were determined by growing 4-inch sod cores in the greenhouse. Panicles were collected from a 7 by 14 inch area and counted to determine panicle density in June 1999, 2000, and 2001. Bluegrass was swathed and seed was harvested at maturity in 2000 and 2001. The 2001 grass seed yield samples are being processed and data will be presented next year in the final report. Objective 1:
In early spring of 2001, C tiller and total panicles in 'Nublue' and total
panicles in 'Rhonde' were not different among intercrop treatments and
the non-suppressed bluegrass control (Table 1). C tiller panicle number
in 'Rhonde', following the 1999 oat intercrop, was 67% greater than the
non-suppressed bluegrass control. Panicle number at harvest of 'Rhonde'
and 'Nublue' was 29 to 49% and 47 to 53% greater following the 1999 oat
and pea intercrops, respectively, compared to the non-suppressed bluegrass
control treatment. Residue level did not affect 'Rhonde' C tiller and
total panicles in early spring and panicle number at harvest in 2001,
which also was the case in 2000. C tiller panicles in early spring and
panicles at harvest were 66 and 24% greater, respectively, in low residue
(burned) areas of 'Nublue' compared to unburned areas in 2001. In 2000,
seed yield of 'Nublue' was 36% greater in burned versus non-burned plots
(see last year's STEEP report). The number of C tiller (expect 'Nublue') and total panicles in early spring and panicle number at harvest in 2001 of 'Nublue' and 'Palouse' were not different among nitrogen treatments (Table 3). C tiller panicles in 'Nublue' and 'Palouse' were 35 and 70% greater, respectively, in burned compared to non-burned plots. Panicle number at harvest in 2001 in 'Palouse' was 50% greater in burned than in non-burned plots. Panicle number at harvest in 2001 in Roundup suppressed (lentil) plots of 'Nublue' was 45% greater than in non-suppressed bluegrass control plots. Objective 3: Fairfield plots were shown to the Spokane Co. Crop Improvement Assoc. during June 1999 and 2000. The Nezperce plots were included in the Lewis County field tour during June 1999 and 2000. INTERACTION WITH OTHER SCIENTIST CONDUCTING RELATED ACTIVIES: No other scientist are conducting related research. PUBLICATIONS AND
PRESENTATIONS: Thill, D.C., J.B.
Swensen, and J. Reed. 2000. Integrated management system for sustained
seed yield of Kentucky bluegrass without burning. 2000 GSGSSA Annual Report.
Pg. 31-34. Thill, D.C., J.B.
Swensen, and J. Reed. 2000. Integrated management system for sustained
seed yield of Kentucky bluegrass without burning. 2000. STEEP Annual Report.
Pg. 121-130; and 2000 Washington DOE annual report. Swensen, J. B., J.
M. Reed, and D. C. Thill. 2000. Roundup suppression and intercropping
Kentucky bluegrass to maintain subsequent bluegrass seed yield. Annual
GSCSSA Meeting. November 30, Kennewick, WA (poster). Swensen, J. B., J. M. Reed, and D. C. Thill. 2001. Glyphosate suppression and intercropping Kentucky bluegrass to maintain subsequent bluegrass seed yield. Proc. West. Soc. Weed Sci. 54:7 Table 1. The effects of intercrops and residue removal methods in 2001 on panicle densities of Kentucky bluegrass (KBG). C tiller and total panicle number were determined in early spring from 4-inch diameter sod cores grown in the greenhouse. Panicles at harvest were counted in the field shortly before seed harvest. Values for intercrops are means of two residue levels, while values for residue levels are means of the four intercrop.
Table 2. The effects
of Roundup application time (applied in spring 1999) and rate, and residue
removal methods on Kentucky bluegrass panicle density in 2001. C tiller
and total panicle number were determined in early spring from 4-inch diameter
sod cores grown in the greenhouse. Panicles at harvest were counted in
the field shortly before seed harvest. Values for herbicide treatments
Table 3. The effects
of nitrogen application time, residue level, and intercrop-type on Kentucky
bluegrass panicle
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