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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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[CATEGORY
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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.
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