Healthy vineyard soils Cover crop management Tilling and grazing trial

Jenna J. Merrilees

Graduate student in Agriculture; Soil Science

Department of Natural Resource Management & Environmental Studies, Cal Poly, San Luis Obispo

June 13th, 2019

Outline

I. Methodology

II. Greenhouse gas results

III. Soil chemical & physical properties (C and N)

IV. Grape yield & berry quality analysis

V. Conclusions

Introduction Cover crops used to

mitigate soil loss and increase soil organic matter to improve soil health

Cover crops may be either

A. mowed and left on the soil surface

B. incorporated into the soil through tillage

Vineyard management influence on soil ecosystem functioning over time

Tablas Creek Vineyard, Paso Robles CA

Tractor row

Vine row

Introduction continued

Sheep grazing is used as an alternative to mowing

It’s unclear whether the removal of organic biomass and inputs of N-rich urine and feces will negatively impact GHGs

Photo: Byrnes, R.C. et al 2018

Objectives

Determine the short-term effects of grazing and tilling on greenhouse gases CO2 and N2O

Determine the influence of management on soil C, N along with active forms of C and N.

Hypothesis

We hypothesized that

tillage would increase CO2

emissions by disturbing

aggregate stability in soils

We hypothesized that

grazing would increase

N2O from N-rich manure

inputs

Six et al. 2000

Site and Method Grapes are a Syrah variety historically under cover crop

and tillage management

Linne-Calodo complex,

30% clay, pH 8.1

Treatment groups each replicated 4 times

1. Grazed + Till

2. Grazed + No-till

3. Non-grazed + Till

4. Non-grazed + No-till (control)

Vine row

Tractor row

Soil organic matter % and active C were highest in the 0-6” in tractor row

[VALUE] %

[VALUE] %

126

Soil depth (in.)

[VALUE] %

[VALUE] %

126

Soil depth (in.)

Vine row Tractor row

Animal grazing

• Grazing density: 150 sheep/acre/day

Cover crop

Soil Max Organic Legume Mix by LA Hearne Seed Co.

100-175 lbs./acre

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Soil greenhouse gas emissions

0

10

20

30

40

50

60

70

kg C

O2-C

ha-1

day

-1

Tractor row

Tractor row

Tillage

Rain Rain Rain Rain Rain

CO2 after tillage & grazing

a

a

a

a

0

200

400

600

800

1,000

1,200

1,400

Non-grazed Grazed Non-grazed Grazed

No-till Till

Cu

mu

lati

ve C

O2 e

mis

sio

ns

(kg

CO

2-C

ha-1

)

Highest in non-grazed tilled tractor rows

Soil C no significant differences in organic C between management after 1 year control has highest

20,000

25,000

30,000

35,000

40,000

45,000

50,000

Non-grazed Grazed Non-grazed Grazed

No-till Till

SO

C k

g C

ha-1

0-6"

6-12"

N2O emissions after tillage & grazing

a,b

a

b

a,b

0

50

100

150

200

250

Non-grazed Grazed Non-grazed Grazed

No-till Till

Cu

mu

lati

ve N

2O

em

issi

on

s h

a-1 d

ay-1

Highest in the no-till grazed vine row soil

N cycling likely influenced by management especially grazing

Management influenced N2O emissions

Relationship to active N forms in soil (No3 and NH4) is not yet clear

Surface-level compaction was lowest in the tilled non-grazed soil

1.01

1.12

0.92

1.15

Non-grazed Grazed Non-grazed Grazed

No-till Till

So

il b

ulk

den

sity

(g

/cm

3 )

Surface-level compaction was lowest in the tilled non-grazed soil

1.01

1.12

0.92

1.15

Non-grazed Grazed Non-grazed Grazed

No-till Till

So

il b

ulk

den

sity

(g

/cm

3 )

Graph Builder

Soil porosity (%)

20 30 40 50 60 70 80 90 100

Active C

(m

g P

OX

C k

g-1

so

il)

0

200

400

600

800R²: 0.484 Active C (POXC) x Soil porosity

T0-6

T6-12

V0-6

V6-12

T0-6: (90%)

T6-12: (90%)

V0-6: (90%)

V6-12: (90%)

Grape yield

Grape yield

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

No-till Till

Fre

sh w

eig

ht

(kg

ha-1

)

Total yield (kg/ha)

Fresh wt. / vine

# clusters / vine

No significant differences between tilling treatments

Berry quality

Berry quality

Physical

Fresh wt. (skins)

Fresh wt. (pulp)

Fresh wt. (seeds)

Fresh wt. (berry)

Chemical

Brix (handheld)

pH

Titratable Acidity

Malic acid (enzymatic)

Anthocyanins

Phenolics

no changes to quality following 1 year of tillage management

Conclusions

No changes in CO2, grape quantity or quality from management

There is an interaction between grazing and tilling on N2O emissions

CO2 emissions likely influenced by amount of available C

Further investigating the role of active soil C and N will give us more insight into how C and N are cycling

Understanding the influence of management on GHGs will inform our knowledge on soil health, long-term GHG rates and C sequestration

Thank you

The staff of Tablas Creek Vineyard, the Center of Sustainability, the Vineyard Team, The California State University Agricultural Research Institute (ARI), & California Department of Food and Agriculture (CDFA) for support on this project.