changes in soil aggregation, soil water

Transcription

Document obtenu sur le site http://Agroecologie.cirad.fr
CHANGES IN SOIL AGGREGATION, SOIL
WATER-HOLDING CAPACITY AND SOIL
BIOLOGICAL ACTIVITY UNDER NO-TILL
SYSTEMS AND CROPPING SEQUENCES IN THE
LAO PDR
By Florent Tivet, Hoà Tran Quoc, Johnny Boyer, Chansamone Inthavong,
Sompasith Senephansiri, Laty Keodouangsy, Thisadee Chounlamountry,
Chanthasone Khamxaykhay, Khamkeo Panyasiri, Lucien Séguy
CONTENT
1.
Brief presentation of the context
in the Southern Xayabury
2.
Materials and methods
3.
Results
4.
Discussion and Prospective
Rising pressure on the natural
environment and on farming
systems…
… to increase productivity to generate
marketable commodities
Marked land
degradation and
depletion of natural
resources
ORIGINAL AND CURRENT SOC –
SOUTHERN XAYABURY
Natural ecosystem
SOM natural (%)
SOC natural (%)
Stock C (ton/ha)
-3
Bulk density (Mg.m )
Converting forest + 15 years of ploughing
SOM current (%)
SOC current (%)
Stock C (ton/ha)
-3
Total loss of carbon (ton/ha)
0-10 cm
7.99
4.64
48.67
1.05
10-20 cm
5.66
3.29
37.78
1.15
2.71
1.57
20.44
1.30
3.00
1.74
23.19
1.33
0-20 cm
86.45
43.64
42.81
SOIL PHYSICAL PROPERTIES UNDER
CONVENTIONAL PRACTICES
St
e,
op
sl
p ge
ee tilla
e,
op
sl e
tle ag
en ill
G t
Soil is disrupted by tillage, high frequency of small macro aggregates is
observed. Increasing mineralization rate and loss of SOC by runoff.
OBJECTIVE
‘This study set out to analyse soil aggregation, soil
water-holding capacity and soil biological activity
under tillage and no-tillage conditions in relation to
the cropping sequence’
CONTENT
1.
in the Southern xayabury
2.
3.
Results
4.
Maize monoculture (4.8 t.ha-1 DM)
THREE CROPPING SYSTEMS
Maize (5.1) / Rice bean (3.1)
Maize (5.2) + B. ruziziensis (4.0) /
Rice bean (3.1)
SOIL AGGREGATION
Water stable aggregates: aggregate size fraction through the wet sieving method
(Yoder, 1936).
Soil samples are collected at 0–10, 10-20 and 20–30 cm depth (6 replicates per
depth).
The samples are moistened by capillarity, by placing them on a filter paper at the
top sieve. The water volume is then raised inside the water tank to wet the filter
paper and, consequently the soil.
Each test uses six sieves of 8, 4, 2, 1, 0.5 and 0.25 mm. The wet sieving process
for 10 minutes. The aggregates retained in each sieve are weighed 24h at 105°C.
SOIL WATER HOLDING CAPACITY
6
Soil samples are collected at 0–10, 10-20 and 20–30 cm depth to measure
bulk density.
The samples are moistened by capillarity until full capacity and then weighted.
7
Weight of dry soil is recorded after drying the sample for 24h at 105°C.
SOIL MACRO FAUNA
Fauna sampling is done on square of 25cmx25cm on the top soil and at 3 depths:
0-10, 10-20 and 20-30 cm.
Minimum of 9 repetitions are required for each system. Total fauna is collected on
each depth using pliers and put into alcohol for identification in laboratory.
Fauna identification and accounting is done under binocular glass. Fauna weight is
done for each treatment at every depth and for each specie.
CONTENT
1.
2.
3.
Results
4.
Frequency (%)
0
10
20
30
40
Forest
Soil layers (cm)
0-10
10-20
20-30
5.6 mm
5.3 mm
8 mm
4 mm
2 mm
1 mm
0.5 mm
0.25 mm
5.1 mm mean diameter of water-stable aggregate
SOIL AGGREGATION
Frequency (%)
0
10
20
30
40
Soil layers (cm)
Tillage
0-10
3.0 mm
10-20
4.6 mm
20-30
4.3 mm
> 8 mm
> 4 mm
> 2 mm
> 1 mm
> 0.5 mm
> 0.25 mm
Frequency (%)
0
10
20
30
40
SCV
Soil layers (cm)
0-10
4.7 mm
10-20
5.0 mm
20-30
4.2 mm
Maize monoculture, DM = 4.8 t.ha-1
Frequency (%)
0
10
20
30
40
Soil layers (cm)
Tillage
0-10
3.3 mm
10-20
3.6 mm
20-30
3.8 mm
> 8 mm
> 4 mm
> 2 mm
> 1 mm
> 0.5 mm
> 0.25 mm
Frequency (%)
0
10
20
30
40
Soil layers (cm)
SCV
0-10
4.9 mm
10-20
4.0 mm
20-30
3.8 mm
Maize (DM = 5.1 t.ha-1) / Rice bean (DM = 3.1 t.ha-1)
Frequency (%)
0
10
20
30
40
Soil layers (cm)
Tillage
0-10
3.6 mm
10-20
3.7 mm
3.4 mm
20-30
> 8 mm
> 4 mm
> 2 mm
> 1 mm
> 0.5 mm
> 0.25 mm
Frequency (%)
0
10
20
30
40
SCV
Soil layers (cm)
0-10
6.0 mm
10-20
5.0 mm
20-30
4.8 mm
Maize (DM = 5.2 t.ha-1) + B. ruziziensis (4 t.ha-1) /
Rice bean (3.2 t.ha-1)
The temporary (roots hairs and
hyphae) and transient
(polysaccharides) binding agents are
the most important aggregation
components.
Frequency (%)
0
10
20
30
40
50
Soil layers (cm)
Brachiaria ruziziensis
0-10
7.4 mm
10-20
7.2 mm
20-30
5.2 mm
>
>
>
>
>
>
8 mm
4 mm
2 mm
1 mm
0.5 mm
0.25 mm
Soil aggregation under [No-till and cropping sequence maize +
B. ruziziensis – rice bean] showed results close to the natural
ecosystem.
Land preparation
Tillage
No-till
Tillage
No-till
Tillage
Cropping sequence
maize monoculture
Water Stable Aggregate (mm)
0-10 cm
c
4.6
b
5.0
c
3.6
b
4.0
c
3.7
a
3.0
4.7
maize - rice bean
3.3
4.9
maize + B. ruziziensis - rice bean
10-20 cm
3.6
20-30 cm
ab
4.3
abc
a
4.2
c
3.8
bc
3.8
c
3.4
a
abc
bc
bc
c
ab
No-till
6.0
5.0
4.8
Forest
5.6a
5.3a
5.1a
SOIL AGGREGATION
SOIL AGGREGATION
DMC maize + B. ruziziensis – rice bean
High frequency of big macro aggregates. Enhanced soil structure, increase soil
water holding capacity and protect soil organic carbon (oxidation reduction).
Soil sensitivity to erosion decreases due to soil cohesion improvement.
Macro aggregation (and pattern of aggregate size) is linked to continuous C flux
(dry matter/residue input) and enhancement of soil biological activity
SOIL AGGREGATION
e,
op
sl ng
p hi
ee ug
St plo
e,
op
sl ing
tle gh
en u
G plo
Soil disrupted by tillage
+
ze i s
ai s
m ien n
C iz ea
M z b
D . ru ice
B –r
Aggreg
ation pr
ocess u
nder no
-till and
sequen
croppin
ce.
g
“The macroaggregation is the main
way to protect the C released from
the crop residues decomposition and
stimulate the interactions among soil
chemical, physical and biological
attributes”
65
Soil water retention (mm H2O, 0-10 cm)
bc
c
ab
bc
a
60
c
a
+8.6
+6.6
55
+7.1
50
45
40
35
30
25
re
Fo
e-
iz
Ma
st
e
Ric
b
n
ea
ize
Ma
-
CV
e
Ric
be
S
an
i-
ruz
+
e
iz
Ma
CV
e
Ric
b
n
ea
i-
iz
Ma
ruz
+
e
CV
e
Ric
be
S
an
CV
ize
Ma
CV
S
ize
a
M
CV
160
Soil water retention (mm H2O, 0-30 cm)
bcd
cd
ab
150
abc
+9.0
a
d
+6.2
ab
+10.4
140
130
120
110
100
90
re
Fo
iz
Ma
e
st
eb
n
ea
ic
-R
e-
iz
Ma
CV
e
Ric
be
S
an
i
iz
Ma
ruz
+
e
CV
eb
ic
-R
e
iz
Ma
n
ea
i-
uz
+r
CV
e
Ric
be
S
an
CV
ize
Ma
CV
S
ize
a
M
CV
SOIL MACRO FAUNA ACTIVITY
2500
CT
No-till
17
17
Individual (m-2)
2000
14
1500
17
18
1000
14
16
10
500
12
12
0
Mo
c
no
iz
ma
e
r
u
ult
e
ize
Ma
b
ice
R
-
ea
n
eb
Ric
e
Ric
ea
a
be
iz
Ma
n
n
aiz
-M
e
B
e+
iz
Ma
. ru
B
e+
ie
ziz
. ru
ns
is
ie
ziz
ns
is
b
ice
R
-
ea
n
SOIL MACRO FAUNA ACTIVITY
30
CT
No-till
Biomass (g.m-2)
25
20
15
10
5
0
n
Mo
oc
ma
e
r
u
ult
ize
iz
Ma
Ric
e
e
eb
an
Ric
Ric
e
eb
e
eb
an
an
aiz
-M
aiz
-M
e
e+
ru
B.
ize
Ma
+B
ien
ziz
sis
ziz
. ru
ic
ien
-R
sis
e
eb
an
SOUTHERN XAYABURY
Between 2001 and 2007
SOM 2001 (%)
SOC 2001 (%)
Stock C 2001 (ton/ha)
-3
SOM 2007 DMC (%) maize - rice bean
SOC 2007 DMC (%)
Stock C (ton/ha)
-3
Total gain of carbon (7 years, ton/ha)
Carbon gain per year (ton/ha)
SOM 2007 CV (%)
SOC 2007 CV (%)
Stock C (ton/ha)
-3
Difference of SOC CV vs SCV
Total loss of SOC between 2001 and 2007
0-10 cm
3.75
2.17
29.76
1.37
10-20 cm
3.50
2.03
27.72
1.37
4.06
2.36
32.29
1.37
3.31
1.92
26.11
1.36
0.36
-0.23
2.71
1.57
21.30
1.36
3.00
1.74
23.80
1.37
-10.98
-8.46
-2.31
-3.92
0-20 cm
57.48
58.40
0.92
0.13
45.10
-13.29
-12.37
Two years rotational sequence. DM of maize = 6,0 t.ha-1 and rice
bean = 3,8 t.ha-1
SOUTHERN XAYABURY
Between 2001 and 2007
SOM 2001 (%)
SOC 2001 (%)
Stock C 2001 (ton/ha)
-3
0-10 cm
3,88
2,25
30,83
1,37
10-20 cm
3,29
1,91
26,09
1,37
SOM 2007 DMC (%) maize - rice bean
SOC 2007 DMC (%)
Stock C (ton/ha)
-3
4,46
2,59
34,74
1,34
3,80
2,21
30,20
1,37
SOM 2007 CV (%) maize - rice bean
SOC 2007 CV (%)
Stock C (ton/ha)
-3
2,71
1,57
21,49
1,37
3,00
1,74
23,78
1,37
-1,75
-13,24
-0,80
-6,42
Difference of OM CV vs SCV
Difference of SOC CV vs SCV
0-20 cm
56,92
64,93
45,27
-19,67
Two years rotational sequence. DM of maize = 10,6 t.ha-1 and rice
bean = 3,8 t.ha-1
CONTENT
1.
2.
3.
Results
4.
DISCUSSION AND PROSPECTIVE
Soil aggregation, water holding capacity and biological
activity increase under no-till and cropping sequence
but…
…we have to generate no-till and intensive (high dry
matter production > 15 t.ha-1) cropping sequence to
optimize the main functions of SCV systems: nutrients
recycling, water use efficiency, integrated weeds
management, SOC sequestration and profitability.
DM = 7.8 t.ha-1 (maize) + 10.6 t.ha-1
(B. ruziziensis + C. cajan)
DM = 7.4 t.ha-1 (maize) + 7.9 t.ha-1
(C. cajan)
DM = 7.2 t.ha-1 (maize) + 4 t.ha-1
(V. umbellata)
Analyze SOC for a range of no-till and cropping sequence in ‘station’ and in
farmers’ fields:
• To record the potentialities of these systems in sequestrating C and
the impact of each specie on the form of C (stable and active pool).
• To establish relationships between SOC and profitability.
H22O
Why the soil
organic
matter
is
Importance of continuous OM flux to
influence soil aggregation, soil
the
key
component
structure and OM
as a consequences
influence
air flux,
water retention, and
of the
no-tillage
nutrients cycling.
AIR systems?
NUTRIENTS
From J.C de Moraes Sà
THANKS FOR YOU
ATTENTION

changes in soil aggregation, soil water

Transcription

Documents pareils

Life Cycle - LCA Forum

resultats-minimes-ca.. - Taekwondo olympique provinois

resultat open labellise 13/02/2016

DFID IED presentation 8th November