This presentation discusses the possibility for using vineyard design to help suppress weeds.

1. Vineyard design and weed suppression:
an example with black nightshade (Solanum nigrum)
Matthew Fidelibus
Extension Specialist
Department of Viticulture and Enology
University of California, Davis

2. Challenges to Weed Control in
San Joaquin Valley (SJV) Vineyards
• Economic: Profit margins are slim and the ‘cost’ of
weeds in mature vineyards is uncertain
• Environmental:
– Air and water pollution are major problems in the SJV
– Regulation of dust emissions may curtail mechanical
controls.
– Herbicide use restricted in some SJV vineyards to protect
groundwater
• Biological: Many weed species are resistant to
common herbicides

3. Weed control a low priority
in some raisin vineyards
Photo courtesy of Kurt Hembree, UCCE

4. Dust emissions from vehicles, equipment and wind
are regulated

5. Herbicide resistant horseweed discovered in SJV, 2005
Photo courtesy of Anil Shrestha, CSUF

6. New production concepts present opportunities to reassess vineyard design
which could affect the ecology of vineyard weeds

7. OBJECTIVES:
Determine whether row orientation of open gable
DOV trellis system affects the light environment of
weeds growing in the rows.
If so, could such differences potentially help manage
weeds?

8. MATERIALS AND METHODS

9. MATERIALS AND METHODS
3-4 leaf black nightshade (Solanum nigrum) plants were
transplanted into 9-l pots

10. MATERIALS AND METHODS
Pots placed beneath the canopy of raisin grapes in rows oriented
East-West (E-W) or North-South (N-S) in April

11. MATERIALS AND METHODS
Quantity and quality of light available to weeds
measured weekly 3-times a day (9 AM, 12 PM, 3 PM).
Photosynthesis and water use of weeds were also measured.

12. MATERIALS AND METHODS
Weeds were harvested 2 months after planting and separated into:
roots, stems, leaves and berries
Leaf area was measured and each plant part was dried and weighed

13. SEASONAL SHADOW PATTERNS
IN THE VINEYARD
East-West North-South
9 AM
12 PM
4 PM
PAR 12 PM
0
400
800
1200
1600
PAR 4 PM
Date
0
400
800
1200
1600
PAR 9 AM
PAR(molm
-2s-1)
0
400
800
1200
1600
NS
EW
5/9 5/27 6/24

14. 0
10
20
30
40
50
6.30
7.30
8.30
9.30
10.30
11.30
12.30
14.30
15.30
16.30
17.30
18.30
19.30
Time of day (hrs)
Lightlevel(%offullsun)
N-S
E-W
Typical light under the grape canopy zones of the N-S and E-W rows
DAILY LIGHT MICROENVIRONMENTS

15. Row
orientation
9 AM 12 PM 4 PM
EW 0.26 0.24 0.24
NS 0.87 0.24 0.82
P-value 0.005 0.81 0.009
Red: Far Red ratio

16. 2004
0 200 400 600 800 1000 1200 1400
EW
NS
2003
PAR ( mol m-2
sec-1
)
0 200 400 600 800 1000 1200 1400
Photosynthesis(molCO2
m-2
s-1
)
0
5
10
15
20
25
Nightshades Need About 30% Full
Sun for Optimal Photosynthesis

17. Clear effects on morphology, but
not in shoot mass
N-S E-WFull sun

18. Leaf characteristics of nightshade
E-W N-S
Larger, thinner leaves in E-W compared to N-S;
This might make them more susceptible to herbicides

19. Nightshade roots
Full sun N-S E-W
Root mass and R:S ratio declined with shade; full sun > NS > EW

20. Leaf
(33%)
Stem
(34%)
Fruit
(18%)
Root
(14%) Leaf
(27%)
Stem
(31%)
Fruit
(24%)
Root
(17%)
E-W N-S
Row Orientation Affected
How the Weeds Used their Resources
Weeds in EW were light deficient; they invested more in
leaves and stems, and less in fruits and roots than weeds in NS

21. Seed return of nightshade
Row
orientation
Berries
(No.)
Seeds/berry
(No.)
Seeds/plant
(No.)
EW 155 47 7151
NS 184 51 8976
P-value .07 .004 .03

22. CONCLUSIONS
• Row direction affected light environment of weeds in this
trellis and spacing system
• The growth and productivity of weeds was dependant on
their to the light environments; weeds in EW rows
produced 20% fewer seeds than weeds in NS rows
• An integrated approach to vineyard design can provide
one of the “many little hammers” needed to help manage
weeds

23. Acknowledgements
Dr. Anil Shrestha
Kimberley Cathline
Jorge Osorio Aguilar