Transcript Introduction to CA

Introduction to Conservation
Agriculture
and
Conservation Farming
P.C. Wall
CIMMYT®
What is Conservation Agriculture?
An array of technologies such as
residue retention, zero- and
reduced tillage, crop rotations,
green manure cover crops,
controlled traffic and raised
beds. When used in combination
these, over time, reduce, and
often revert, the degradation of
soil and water resources.
Residue retention distinguishes
conservation agriculture from
conventional agriculture, and all
conservation systems include at
least a certain level of surface
residue cover.
Some Characteristics of
Conservation Agriculture
• Comprises two basic
components
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
Surface crop residue
retention
Minimal soil movement
Some Characteristics of
Conservation Agriculture
Plus other components essential to
overcome problems that emerge
once crop residues are retained:


Crop rotation
(Green manure cover crops)
Conservation Agriculture is a
complex technology: it involves
a complete change in the
agricultural system.
Why the term “Conservation
Agriculture”?
• To distinguish it from Conservation Tillage
= 30% ground cover after seeding
• Take the emphasis off the word “tillage”
Why Soil Tillage?
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Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Why Soil Tillage?
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Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Conservation
Agriculture with
Planting Basins
Both the basins and the
mulch provide benefits
– together they provide
the optimum
Why Soil Tillage?
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Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Nitrogen mineralization implies
organic matter breakdown
• It is a “quick fix”. It is a dwindling shortterm gain that causes long-term harm.
• The release of nitrogen after tillage comes
in a “flush” and considerable amounts may
be lost.
• In conservation agriculture organic matter
breakdown is reduced, and so a little more
nitrogen must be added to the system, at
least for the first few years.
Effect of Tillage on Soil
Rhizobium Populations
60
Rhizobium cells
50
40
30
20
10
0
Zero Tillage
From Voss and Sidiras, 1985
Conventional Tillage
Why Soil Tillage?
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•
•
•
•
•
•
•
Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Why Soil Tillage?
•
•
•
•
•
•
•
•
Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Effect of Tillage on Soil Phosphorus
Soil Depth (cm.)
Oxisol Conv
Oxisol Zero
Alfisol Conv
Alfisol Zero
0-10
10-20
20-40
40-60
0
10
20
30
P (ppm)
Adapted from Sidiras and Pavan, 1985
40
50
Effect of Tillage on Soil pH
Soil Depth (cm.)
Oxisol Conv
Oxisol Zero
Alfisol Conv
Alfisol Zero
0-10
10-20
20-40
40-60
0
2
4
pH
Adapted from Sidiras and Pavan, 1985
6
8
Effect of Tillage on Soil Organic Carbon
Soil Depth (cm.)
Oxisol Conv
Oxisol Zero
Alfisol Conv
Alfisol Zero
0-10
10-20
20-40
0
0.5
1
1.5
Organic Carbon %
Adapted from Sidiras and Pavan, 1985
2
2.5
Effect of Tillage on Earthworm Populations
2
Earthworms/m
Oxisol
30
25
20
15
10
5
0
Conv.
Alfisol
Vert.
Zero
Source : Derpsch et al., 1991.
Oxisol :- 0-30 cm. after 4 years
Alfisol :- 0-10 cm. after 1.5 years
Why Soil Tillage?
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Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Monoculture leads to a build-up of
pests and diseases. This is far more
marked in zero tillage than in
conventional tillage
The key to controlling pests and diseases
in zero tillage agriculture is crop
rotation. One should avoid seeding a
crop into it’s own residues before these
are decomposed.
Why Soil Tillage?
•
•
•
•
•
•
•
•
Weed Control
Prepare a seed-bed
Mineralise nitrogen
Eliminate compacted zones
Incorporate fertilizers and ammendments
Control diseases and pests
Control water run-off
Accumulate water
Effect of Tillage on Water Erosion
Conventional Tillage
Vertical Tillage
Zero Tillage
Soil Loss (t/ha/year)
Brazil
Paraguay
(Sidiras) (Venialgo)
68.2
22.9
55.0
6.9
0.5
Why Soil Tillage?
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Weed Control
Prepare a seed-bed
Mineralize nitrogen
Eliminate compacted zones
Incorporate fertilizers and amendments
Control diseases and pests
Control water run-off
Accumulate water
Effect of Tillage and Residue
Cover on Water Infiltration
Treatment
Deep plough, disc
% Residue % Water Soil Loss
Cover
Runoff
t/ha
0
90
28.5
Rip, disc
10
70
6.7
Chisel plough,
cultivate
Zero tillage
30
34
1.6
80
6
1.0
63mm in 1 hour – 4% slope.
Cedara Agric. Res. Stn, Kwazulu-Natal, RSA
Aesthetics!
World wide adoption of Zero-tillage 2002
Millions of hectares
Total = 67 million ha.
Rest of the World 1.4
Canada 4.1
USA 21.1
China 1.0?
IGP 0.2
Ghana: 100.000 small
Brazil 17.3
farmers use NT
Paraguay 1.3
Australia
Argentina 11.7
9.0
Based on Derpsch 2002
Farmers Perceptions of the Benefits of
Conservation Agriculture
Benefit
Lower labour requirement
Simplifies labor management
Reduced drudgery
Fuel savings
Increased machinery use efficiency
Can expand planted area with existing resources
Reduces production costs
Higher yields, especially in drought years
Can seed more of the crop at optimum time
Avoid re-seeding of crops
Longer tractor life
Reduces soil erosion
Facilitates weed control
Facilitates pest control
Reduced fertilizer requirements
a
Very dependent on region and limiting factors.
Perceived by:
Large Farmers
Small Farmers
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The principles of conservation
agriculture appear to have
extremely wide application
The actual formulae and
technologies for applying
these principles are very sitespecific.