2000 Table of Contents

2000 STEEP III Progress Report

RESEARCH PROJECT TITLE: Integrated Management System for Sustained Seed Yield of Kentucky Bluegrass Without Burning.

INVESTIGATORS:

Donn Thill, Univ. Idaho, and Bill Johnston, Wash. State Univ.

INTERIM REPORT:

PROJECT OBJECTIVES:

1. To determine variety and location influence on Roundup suppression of bluegrass, seed yield of three no-till crops, and subsequent bluegrass seed yield for two years.
2. To relate bluegrass seed yield response to Roundup rate and timing, timing of nitrogen application, and proportion of productive tiller categories.
3. To disseminate information to growers via field representatives, extension educators, field tours, and practical publications and to scientific audiences via publications and presentations.
   

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. In March 1999, following a spring Roundup application, tiller densities in recovering stands of bluegrass were lowest in early flowering varieties, and averaged 7, 13, 20, and 51% of non-renovated control plots in 'Palouse', 'Kenblue', 'Rhonde', and 'Nublue', respectively. In general, later application timings of Roundup resulted in lower bluegrass recovery. Seed yield of the oat intercrop was greater than pea or lentil. Recovery of bluegrass was variety (location) specific the year following renovation. In summer 2000, bluegrass seed yield for 'Nublue' was greatest when pea was the intercrop and least for oat and the non-renovated bluegrass. Seed yield of 'Nublue' was 1.6 times greater in low residue (burned) compared to high residue (not burned) plots. 'Rhonde' seed yield was greatest when lentil was the intercrop and least for oats and the non-renovated bluegrass. Seed yield was equal in low and high residue plots. Except for the very earliest application times (6 and 5 weeks before planting), 'Palouse' did not recover from Roundup treatment. Successful renovation of Kentucky bluegrass stands with Roundup depends greatly on selecting the optimum application time during spring of the renovation year, which is affected by both bluegrass variety and environment.

RESULTS AND INTERPRETATION:

See the 1999 GSCSSA and STEEP reports for last year's information. Following harvest in 1998, trials were established in fields of 'Rhonde', 'Kenblue', 'Nublue', and 'Palouse' Kentucky bluegrass, each with an intercrop experiment and a 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 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-renovated bluegrass control plots (no Roundup or intercrop). For specific agronomic practices see the previous year STEEP progress report. In July 1999, non-renovated bluegrass plots were swathed. Windrows and standing intercrops were harvested with a plot combine to determine seed yield. The 'Kenblue' site was inadvertently plowed up and is no longer part of the study. Following harvest in 1999, post harvest residue was removed from the bluegrass control plots using the same methods as in 1998. 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, 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 to 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 and 2000 panicles derived from C and F tillers were determined by growing 4-inch sod cores in the greenhouse. In June 2000, panicles were collected from a 7 by 14 inch area and counted to determine panicle density. Bluegrass was swathed and harvested at maturity during summer 2000.

Objective 1: Density of C-tillers and total tillers in fall 1999 was highest in the non-renovated controls and lowest in the intercrop plots of 'Rhonde' and 'Palouse' (Table 1). Fall C-tillers and total tillers were lowest in the oat intercrop plots of 'Nublue'. By spring, however, C- and total panicle density in control plots was less than in pea and lentil intercrops of 'Nublue', and equal to intercrops of 'Rhonde'. Panicle density at harvest was lowest in the oat intercrop of 'Nublue' and equal among 'Rhonde' treatments. Bluegrass seed yield following pea and lentil intercrops was 1.6 to 2.3 times greater than the unrenovated controls of 'Nublue' and 'Rhonde'. Residue level did not affect 'Rhonde' seed yield, however, yields were 1.6 times greater in low residue (burned) areas of 'Nublue' compared to unburned areas. C-tiller density of all three bluegrass varieties during fall 1999 was not significantly influenced by residue level. However, 'Nublue' had significantly more panicles at harvest in low (burned) compared to high residue areas, averaging 270 and 186 panicles/ft², respectively. Post-glyphosate recovery of 'Palouse' was too low, and no data were collected from these plots after March 2000.

Objective 2: This paragraph briefly reviews findings from the 1998-1999 crop year (see 1999 STEEP Report). Non-renovated plots of 'Rhonde' and 'Palouse' had a similar number of C-tillers in high and low residue plots, averaging 311 and 378 C-tillers/ft², respectively, in fall 1998; 15 and 224 tillers/ft², respectively, in spring 1999; and 51 and 196 panicles/ft², respectively, at harvest in summer 1999 [note - there were 40% fewer panicles in high residue (not burned), compared to low residue, 'Palouse' at harvest in 1999]. In low (burned) residue plots of 'Nublue', C-tiller density was about the same in fall 1998 and spring 1999, averaging 176 C-tillers/ft². In high residue plots 'Nublue' C-tiller density was 684 tillers/ft² in fall 1998 and dropped to 49 C-tillers/ft² in spring 1999. At harvest, panicle density in non-renovated 'Nublue' plots was 323 and 143 panicles/ft² in low and high residue plots, respectively. Bluegrass seed yields in 1999 from non-renovated 'Nublue' and 'Palouse' were higher in low residue plots, averaging 245 and 272 lb/A, respectively, compared to 162 and 166 lb/A, respectively, in high residue plots. 'Rhonde' seed yield was not affected by residue level and averaged 107 lb/A. Weight of harvested bluegrass seed averaged 36 mg/100 seeds and was not affected by residue level. Total germination was unaffected by residue level and ranged from 85 to 92%.

Density of fall 1999 C and total tillers usually was highest in the non-renovated controls and lowest in plots treated with Roundup 2 weeks before planting intercrops (Table 2). However, spring 2000 C and total tillers in the non-renovated controls usually were equal to or less than all Roundup application timings for 'Nublue' and 'Rhonde'. Except for the earliest application timings (6 and 5 weeks before seeding the lentil intercrop), stands of Palouse did not recover from Roundup treatment. In fall 1999, C-tillers and total tillers of 'Rhonde', 'Nublue', and 'Palouse' were not affected by residue levels. Bluegrass seed yield of 'Nublue' was 1.9 to 2.6 times greater in Roundup renovated plots compared to non-renovated plots. 'Rhonde' seed yield in renovated plots was equal to or greater than non-renovated plots. In all varieties, low residue plots had densities of spring C-tillers, total tillers and panicles, and seed yields that were greater than or equal to those in high residue plots.

C-tillers were lower when fall nitrogen was applied at 30% of field rate in 'Nublue' (Table 3). Panicle density and seed yield was highest when fall nitrogen was 100% of field rate. Nitrogen timing did not affect panicle density or seed yield of 'Palouse'. In both 'Nublue' and 'Palouse' all measures of panicle density and seed yield were higher in low residue (burned) areas compared with high residue. Non-renovated plots of 'Nublue' had lower panicle densities and seed yields than renovated (lentil) plots, while control plots had higher panicle density than renovated plots of Palouse (poor stand recovery following Roundup application).

INTERACTION (COOPERATION) WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY:

Objective 3: Fairfield plots were shown to the Spokane Co. Crop Improvement Assoc. on June 14, 2000. The Nezperce plots were included in the Lewis County field tour on June 30, 2000.

PUBLICATIONS AND PRESENTATIONS:

Thill, D.C., J.B. Swensen, and J. Reed. 1999. Integrated management system for sustained seed yield of Kentucky bluegrass without burning. 1999 GSGSSA Annual Report.

Thill, D.C., J.B. Swensen, and J. Reed. 1999. Integrated management system for sustained seed yield of Kentucky bluegrass without burning. 1999 STEEP Annual Report. Pg. 121-130; and Washington DOE annual report.

Table 1. The effect of renovation crop type on tiller and panicle densities, and seed yields of three Kentucky bluegrass (KBG) varieties. Values for crop type are means of two residue levels and four replications, while values for residue levels are means of four crop types and four replications.

Variety Rhonde (Fairfield, WA)

Table 1. (continued)

Variety Nublue (Nezperce, ID)

Variety Palouse (Nezperce, ID)

Table 2. The effects of glyphosate timing and rate on fall and spring tiller and panicle densities and seed yield one year after application. Values are means of two residue levels and four replications. Values for residue levels are pooled over Roundup rates.

Variety Rhonde

^a Application timing is weeks prior to planting intercrop.

Table 2. (continued)

Variety Nublue

Table 2. (continued)

Variety Palouse

Table 3. The effects of nitrogen application timing, residue level, and renovation on panicle and tiller density and seed yield on two Kentucky bluegrass varieties in spring 2000. Values are pooled means.

Variety Nublue

Table 3. (continued)

Variety Palouse

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