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Viticultural research on Long Island, 2016
Gauging vine water status
A.Wise, Sr. Issue Educator, Viticulturist
A.Gardner, Grape Program Assistant
Summary
The Long Island wine region focuses on the production of high quality vinifera winegrapes.
Three of the most important attributes of quality, particularly for red winegrapes, are vine
phenology, vine nitrogen status and vine water status (4, 5). Since Long Island vines are grown
on sandy soils with drip irrigation, it is important to understand how to assess and manipulate
vine water status. Mild water stress in the pre-veraison period, for example, contributes to
improvement in flavor and color in red winegrapes (4, 5). Currently, evaluation of vine water
stress is based on visual cues and vineyard manager experience. A pressure chamber (PC),
instrumentation that is standard practice in irrigated winegrape regions, was used to measure
vine water status over a range of scenarios. Of particular interest are plots maintained with
under vine mowing and or cover crops, practices gaining favor as a means to tame vigorous
vines and reduce herbicide use. Several under vine treatments, mowing, fescues and
glyphosate were compared in a Merlot block in 2016. There were no differences in PC readings
among treatments. Under vine mowing reduced cluster weight and the number of
berries/cluster compared to vines maintained with glyphosate. There were no differences in
fruit ripening among treatments. A demonstration trial in a commercial Cabernet Franc block
had variable PC results. Vines seeded with fescue had lower levels of nitrogen and potassium
compared to adjacent plots maintained with herbicides. We expect to see more treatment
effects in 2017 when the ground covers are better established.
Materials and Methods
Fescue plots were established as follows:
1. Long Island Horticultural Research & Extension Center (LIHREC), Riverhead – Merlot, 20 yrs.
old, VSP trained. Treatments:
 Under vine mowing with an Edwards front mounted, single side mower.
 Glyphosate, applications in June and July.
 No mow mix from local ag dealer, includes 5 types of fescue.
 NVO 50/50 grass mix, perennial rye and creeping red fescue.
Establishment and management details available upon request. Plots were 2-3 panels,
replicated 4x each.
423 Griffing Avenue, Suite 100 • Riverhead, New York 11901-3071 • 631.727.7850 • www.ccesuffolk.org
Cornell Cooperative Extension is an employer and educator recognized for valuing AA/EEO, Protected Veterans,
and Individuals with Disabilities and provides equal program and employment opportunities.
2. Cabernet Franc, North Fork commercial vineyard, VSP trained. No mow mix seeded May,
2016 on a moderate domed site and in a low lying section of vineyard with excess vigor.
Adjacent plots maintained with herbicides were used for comparison. Not replicated.
Seeded fescue cover crop vs. grower standard treatment, 2016.
Data collection
 Shoot length: Shoots were measured at LIHREC on 3 dates in June.
 Weed surveys: Done 5x at LIHREC to gauge establishment and percent cover. Data available
upon request.
 Pressure chamber: A PMS Instruments Model 615 pressure chamber was purchased in July.
Periodic readings were taken at both sites. If water stress reached the designated threshold of 12 Bar, vines would be irrigated or cluster thinned and follow up measurements will be taken.
 Lysimeters: Lysimeters were installed in this block several years earlier. Six were replaced in
spring 2016. Lysimeters are PVC pipes with a porous ceramic cap. When pressurized, soil water
is drawn into the ceramic cap. This can be extracted and analyzed for the presence of nitrates.
Nitrate contamination of groundwater is an issue on Long Island; therefore, it is important to
seek vineyard management strategies that reduce leaching.
 Berry samples: Berry samples were collected from both sites prior to harvest, 100
berries/plot. Samples were processed for Brix, titratable acidity (TA) and pH at LIHREC. Samples
were not sent for methoxypyrazine or malate analysis (both measures of ripeness) due to slow
establishment of fescue plots and similarities in PC readings. In 2017, fescue plots should be
better established and therefore any differences should be apparent. We will then send berry
samples for these analyses.
 Harvest data: Collected October 20 at LIHREC. Individual vines were harvested, clusters
counted and crop weight/vine determined. Berries/cluster were counted on random sample of
10 clusters/plot for a total of 40 clusters/treatment.
 Pruning weights: Pruning weights have not been collected at LIHREC as of this writing but
were collected at the commercial vineyard on January 4, 2017.
 Data from the LIHREC trial was analyzed using one way anova via the JMP statistical
program. A Tukey’s test was used for means separation.
Results and Discussion
Shoot length: Though averages were lower for mowed and no mow plots compared to
glyphosate plots, there were no statistical differences between treatments. In past projects
evaluating under vine fescue, there have been few differences in shoot length or caliper (6).
However, differences in the number, length and caliper of laterals in the upper canopy were
consistently observed. Unfortunately, this is difficult data to capture in a VSP-managed vineyard
unless willing to forego summer hedging of green shoots. This is risky in terms of disease
management (downy mildew) and could impact fruit quality, skewing those results.
Pressure chamber: The pressure chamber was purchased in July. We focused on stem water
potential, reflective of what is happening in the plant xylem (vine), rather than leaf WP,
reflective of the water status of that individual leaf. Pressure chambers measure the amount of
pressure required to cause water to appear at the cut surface of the petiole. Pressure is
measured in bars, with one bar = 14.5 psi. The higher (more negative) the reading, the more
significant the water stress. California references discuss -10 to -12 Bar as triggers for irrigation
when using leaf water potential (1, 3). For stem water potential, the approximate threshold is
approximately -9 Bar (2).
When taking readings, the goal was to minimize outside influences. Our protocol follows:
 Readings were restricted to ~ 2 hours around solar noon and only on sunny days.
 Leaves selected were in full sun, west side, mid-canopy, just above the cluster zone.
 2 readings/rep (8 lvs/trt) were taken at LIHREC, 5 readings/treatment in Cabernet Franc
vineyard. ~30 leaves was the practical limit for the 2 hr time period.
 Foil bags were put on target leaves for at least 15 minutes prior to readings.
 We avoided leaves with any kind of rip or tear as that can influence the reading. That
eventually made selection of leaves difficult in the commercial vineyard. After review with PC
experts, it may be possible to use injured leaves if the injury is minor and has healed.
Pressure chamber used for gauging vine water status.
Table 1. LIHREC Merlot, pressure chamber readings, 2016
Stem water potential, Bars
Treatments
July 14 July 22 Aug. 15 Oct. 18
1
Under vine
-2.71
-3.56
-7.59
-5.25
mowing
2
Glyphosate
-3.03
-3.03
-6.72
-5.19
2 applic.
3
No mow
-3.00
-3.75
-7.12
-5.31
fescue mix
4
Per.rye/cr.red -3.38
-4.16
-7.04
-5.58
fescue mix
Significance1
ns
ns
ns
ns
1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.
Irrigation for the LIHREC research vineyard is not separated into zones. Consequently, this
Merlot was irrigated as much as a separate block on much sandier soil. In 2017, we plan to
install shut off valves to provide more appropriate irrigation for this block. There were no
differences between treatments at LIHREC though means in the glyphosate plots were slightly
lower (less water stress).
Table 2. Cabernet Franc, commercial vineyard, pressure chamber readings, 2016
July 27
Aug. 19
Fescue, low area
-7.7
-7.85
Fescue, hillside
-5.1
-6.3
Herbicide, low area
-5.5
-5.6
Herbicide, hillside
-5.05
-7.05
Long Island experienced a moderate drought late June through mid-August. Non-irrigated vines
on dry sites displayed drought stress. Due to periodic rainfall and irrigation at this site, vines
never reached the stem water potential threshold of -9 Bar. There were no visual signs of
drought stress. Further testing was not done due to the application of over the row nets.
Lysimeter results
We collected samples once in May and once in June. Repeated attempts to collect samples
were made throughout the summer with a focus on days after moderate to heavy rainfall.
Unfortunately, predominantly dry weather in July and August prevented the collection of
additional samples.
Statistics were not performed due to the variable number of samples. Some lysimeters readily
provided samples while others were less reliable. In some cases, averages represent only 2
values. Also, in June the highest values occurred in one vineyard row with treatments 2 through
4. This suggests an increased rate of nitrogen fertilization on that row.
In a previous study, there were no differences in lysimeter results between glyphosate and
fescue plots (6). However, on several dates, there was an increase in nitrogen leaching from
under vine clover plots.
Table 3. LIHREC Merlot, lysimeter results, 2016
ppm NO3-N
Treatments
5-6-16
6-10-16
1
2
3
4
Under vine mow
Glyphosate
No mow mix
Rye, fescue mix
avg.
0.14
0.21
0.22
0.87
range
0.1-0.18
0.1-0.38
0.1-0.42
0.1-1.01
avg.
0.97
5.85
3.09
2.03
range
0.1-2.62
0.1-10.75
0.1-6.10
0.1-5.72
Tissue nutrient analyses
Table 4. LIHREC Merlot, petiole analysis, Aug. 18, 2016
percent
Treatments
N
K
P
Ca Mg Mn
1 Under vine mow 0.56 3.31 0.65 1.43 0.64 41.67
0.60 3.41 0.79 1.51 0.75 60.25
2 Glyphosate
No
mow
mix
0.59 2.70 0.59 1.35 0.78 49.00
3
4 Rye, fescue mix 0.56 2.97 0.62 1.38 0.76 40.00
Significance1
ns
ns
ns
ns
ns
ns
Fe
ppm
Cu
B
Zn
%
S
27.23
25.10
58.90
65.88
ns
5.36
5.57
5.53
5.30
ns
33.57
33.73
34.98
33.68
ns
74.57
75.10
78.18
71.00
ns
0.103
0.133
0.105
0.100
ns
1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.
Among the treatments in this Merlot block, there were no statistically significant differences in
nutrient levels. We expected glyphosate plots to be slightly higher in nitrogen but this was not
the case. There were a few interesting trends such as higher P and Mn in glyphosate vs. others.
Table 5. Commercial Cabernet Franc, petiole analysis, Aug. 19, 2016
percent
Treatment Location
N
K
P
Ca
Mg
Mn
Fescue
Fescue
Herbicide
Herbicide
Low spot
Hillside
Low spot
Hillside
0.74
0.64
0.96
0.76
2.81
1.61
3.34
2.35
0.659
0.475
0.421
0.665
1.49
1.47
1.71
1.67
0.615
0.791
0.739
0.862
85
111
68
98
Fe
ppm
Cu
B
Zn
%S
13.0
12.9
13.9
13.8
14.22
13.17
13.77
11.63
29.4
28.5
33.6
31.7
84.4
78.9
70.8
89.2
0.14
0.11
0.12
0.13
Statistical analysis was not possible as plots were not replicated. Nitrogen trended higher in the
low areas (heavier soil) and higher in herbicide plots. Under vine fescue is known to compete
with vines for both nitrogen and water (6, 7, 8, 9). We expect this result to be similar in 2017.
Harvest data
Table 6. LIHREC Merlot, yield components, Oct. 20, 2016
Cluster no/
Cluster wt.
Treatments
vine
lbs.
1 Under vine mowing
19.1 a
0.49 a
2 Glyphosate , 2 applic.
17.8 ab
0.55 b
3 No mow fescue mix
17.2 b
0.51 ac
Per.rye/cr.red
fescue
mix
4
16.8 b
0.54 bc
Significance1
0.0026
0.0017
Crop wt./
vine, lbs.
9.2 ab
9.6 a
8.6 b
9.0 ab
0.0047
Berries/
cluster
130.6 b
153.5 a
149.6 ab
149.0 ab
0.0254
1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.
In practical terms, the most interesting results are the higher cluster weight and lower
berries/cluster in the mowing plots compared to glyphosate plots.
Table 7. LIHREC Merlot, berry characteristics, Oct. 20, 2016
Titratable
Treatments
°Brix
acidity, g/l
1 Under vine mowing
22.5
5.27
2 Glyphosate, 2 applic.
22.3
5.33
3 No mow fescue mix
22.3
5.50
4 NVO 50/50 vineyard mix
22.4
5.28
Significance1
ns
ns
pH
3.56
3.55
3.50
3.51
ns
Berry
wt. – g.
2.08
2.08
1.95
1.93
ns
1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.
Vines experiencing mild drought stress purportedly can show an increase in fruit quality, small
berries for example. Major drought stress would hinder ripening. There were no statistical
differences among treatments. Our results mirror results seen in prior research conducted on
Long Island and in Virginia (6, 7, 8, 9).
Table 8. Commercial Cabernet Franc, berry characteristics, Sept. 20, 2016
°Brix
TA, g/l
pH
Berry wt.g.
Fescue
Low spot
18.6
5.5
3.20
1.88
Hillside
18.8
6.4
3.22
1.88
Herbicide
Low spot
18.0
4.2
3.35
2.03
Hillside
18.9
5.4
3.31
1.96
Statistical analysis of this data was not done as plots were not replicated. Variation in titratable
acidity readings could be due to variations in vine size, plant health and/or crop level.
Pruning weights: In the Merlot block, vines maintained with glyphosate were larger and had
more shoots than those maintained with mowing. The fescue plots were intermediate; it is
possible as those become better established in 2017, a treatment effect may occur. With the
demonstration trial, averages reflect data from 6 vines/plot. The results suggest that the fescue
mix decreased shoot number and vine pruning weights even in the establishment year.
Table 9. Dormant pruning data, LIHREC Merlot, Feb. 27, 2017.
Pruning wt.
Shoot no.
Treatments
– lbs./vine
/vine
1 Under vine mowing
1.37 a
12.8 a
2 Glyphosate, 2 applic.
1.72 b
14.6 b
3 No mow fescue mix
1.48 ab
13.6 ab
4 NVO 50/50 vineyard mix
1.48 ab
13.3 ab
1
Significance
0.0179
0.0213
Cane
weight-lbs.
0.11
0.12
0.11
0.11
ns
1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.
Table 10. Dormant pruning data, Cabernet Franc, Jan. 4, 2017.
Under vine
Landscape
Pruning wtShoot no.
treatment
location
lbs./vine
/vine
Fescue mix
Low spot
1.13
12.9
“
Sandy hillside
1.42
14.3
Herbicide
Low spot
2.31
17.9
“
Sandy hillside
2.15
15.3
Cane
weight- lbs.
0.09
0.10
0.13
0.14
Conclusion
A pressure chamber (PC) was used to gauge vine water status in two under-vine cover crop
trials examining the use of fescue to tame excessive vine vigor. There were no significant
differences between treatments in pressure chamber readings. Vines did not reach the targeted
PC threshold largely due to irrigation. There were small differences between treatments in
cluster weight and berries/cluster. We expect to find more differences in 2017 as fescue plots
should be more fully established. We plan to start PC readings in June and aim for readings
every 2 weeks. We also plan to install shut off valves on irrigation lines in the LIHREC Merlot.
These vines are on slightly heavier Riverhead sandy loam soil and do not require as much water
as the vineyard block located directly to the north (site of the LIHREC variety trial). It will allow
us to more accurately determine effects of the under vine treatments on vine water status. We
need to closely watch vines for signs of drought stress as in 2017 and link those to PC readings.
A long term goal is to relate visual cues and PC readings to vine health and fruit quality. This
type of information is crucial for understanding and fine tuning management practices for
production of quality fruit.
Acknowledgements
We thank Long Island growers for providing matching funds to the New York Wine & Grape
Foundation, who then generously funded this project. We also thank the NY Farm Viability
Institute for their generous support. Many thanks to Pellegrini Vineyards for hosting the
demonstration plots.
References
1. Bogart, K. Measuring Winegrape Water Status Using a Pressure Chamber.
http://articles.extension.org/pages/33029/measuring-winegrape-water-status-using-a-pressurechamber.
2. Lakso, A. Personal communication, e-mail Jan. 23, 2017. Dr. Lakso is a world renowned expert on
grapevine water relations.
3. Shackel, K, UC Davis Dept. of Plant Sciences. Fact sheet: The pressure chamber aka the ‘pressure
bomb’. http://fruitsandnuts.ucdavis.edu/pressure_chamber/.
4. Van Leeuwen, C. Presentation given to Long Island winegrowers, Nov. 20, 2105, Riverhead, NY.
Cornelius ‘Kees’ Van Leeuwen is a Professor of Viticulture, Viticulture oenologie – ISVV, Bordeaux
Sciences Agro & Consultant for Chateau Cheval Blanc, St. Emilion.
5. Van Leeuwen, C, Tregoat, O, Choné, X, Bois, B, Pernet, D and Gaudillère, J.-P. 2009. Vine water
status is a key factor in grape ripening and vintage quality for Bordeaux red wine. How can it be assessed
for vineyard management purposes. J. Int. Sci. Vigne Vin 43, no. 3, pp.121-134.
6. Wise, A, Tarleton, E., Vanden Heuvel, J. Innovative under trellis management for vineyards.
Northeast SARE annual reports, 2012-2014. http://mysare.sare.org/sare_project/lne12-322/
7. Wolf, T. Investigating cover crops as means of vigor control. In Viticulture Notes newsletter, Sept‐
Oct. 2009, vol. 24, no. 3, Virginia Tech, Winchester, VA.
8. Wolf, T. Optimized grape potential through root system and soil moisture manipulations: a research
update. In Viticulture Notes newsletter, Mar‐Apr 2011, vol. 26, no. 2, Virginia Tech, Winchester, VA.
9. Wolf, T. Presentation at the viticulture session of the Long Island Agricultural Forum, January 13,
2017.