Vineyard design and weed suppression: an example with black nightshade (Solanum nigrum)

Matthew FidelibusExtension Specialist

Department of Viticulture and EnologyUniversity of California, Davis

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

Weed control a low priority in some raisin vineyards

Photo courtesy of Kurt Hembree, UCCE

Dust emissions from vehicles, equipment and windare regulated

Herbicide resistant horseweed discovered in SJV, 2005

Photo courtesy of Anil Shrestha, CSUF

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

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?

MATERIALS AND METHODS

MATERIALS AND METHODS

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

MATERIALS AND METHODS

Pots placed beneath the canopy of raisin grapes in rows orientedEast-West (E-W) or North-South (N-S) in April

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.

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

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

PA

R ( m

ol m

- 2 s

-1) 0

400

800

1200

1600NS EW

5/9 5/27 6/24

0

10

20

30

40

50

Time of day (hrs)

Ligh

t lev

el (%

of f

ull s

un)

N-S

E-W

Typical light under the grape canopy zones of the N-S and E-W rows

DAILY LIGHT MICROENVIRONMENTS

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

2004

0 200 400 600 800 1000 1200 1400

EWNS

2003

PAR (mol m -2 sec-1)

0 200 400 600 800 1000 1200 1400

Photosynthesis (

m

ol CO

2 m

-2 s

-1)

0

5

10

15

20

25

Nightshades Need About 30% Full Sun for Optimal Photosynthesis

Clear effects on morphology, but not in shoot mass

N-S E-WFull sun

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

Nightshade rootsFull sun N-S E-W

Root mass and R:S ratio declined with shade; full sun > NS > EW

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

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

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

Acknowledgements

Dr. Anil Shrestha Kimberley CathlineJorge Osorio Aguilar