2. 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.
3. Some Characteristics of
Conservation Agriculture
• Comprises two basic
components
Surface crop residue
retention
Minimal soil movement
4. 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)
6. Why the term “Conservation
Agriculture”?
• To distinguish it from Conservation Tillage
= 30% ground cover after seeding
• Take the emphasis off the word “tillage”
7. 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
8.
9.
10.
11. 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
16. 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
17. Nitrogen mineralization implies
organic matter breakdown
• It is a “quick fix”. It is a dwindling short-
term 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.
18.
19. Effect of Tillage on Soil
Rhizobium Populations
60
50
Rhizobium cells
40
30
20
10
0
Zero Tillage Conventional Tillage
From Voss and Sidiras, 1985
20. 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
21.
22.
23.
24. 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
25. Effect of Tillage on Soil Phosphorus
Oxisol Conv Oxisol Zero Alfisol Conv Alfisol Zero
0-10
Soil Depth (cm.)
10-20
20-40
40-60
0 10 20 30 40 50
P (ppm)
Adapted from Sidiras and Pavan, 1985
26. Effect of Tillage on Soil pH
Oxisol Conv Oxisol Zero Alfisol Conv Alfisol Zero
0-10
Soil Depth (cm.)
10-20
20-40
40-60
0 2 4 6 8
pH
Adapted from Sidiras and Pavan, 1985
27. Effect of Tillage on Soil Organic Carbon
Oxisol Conv Oxisol Zero Alfisol Conv Alfisol Zero
0-10
Soil Depth (cm.)
10-20
20-40
0 0.5 1 1.5 2 2.5
Organic Carbon %
Adapted from Sidiras and Pavan, 1985
28.
29. Effect of Tillage on Earthworm Populations
Oxisol Alfisol
30
Earthworms/m
2
25
20
15
10
5
0
Conv. Vert. Zero
Source : Derpsch et al., 1991.
Oxisol :- 0-30 cm. after 4 years
Alfisol :- 0-10 cm. after 1.5 years
30. 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
31. 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.
32. 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
33.
34. Effect of Tillage on Water Erosion
Soil Loss (t/ha/year)
Brazil Paraguay
(Sidiras) (Venialgo)
Conventional Tillage 68.2 22.9
Vertical Tillage 55.0
Zero Tillage 6.9 0.5
35. Why Soil Tillage?
• 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
36. Effect of Tillage and Residue
Cover on Water Infiltration
Treatment % Residue % Water Soil Loss
Cover Runoff t/ha
Deep plough, disc 0 90 28.5
Rip, disc 10 70 6.7
Chisel plough, 30 34 1.6
cultivate
Zero tillage 80 6 1.0
63mm in 1 hour – 4% slope.
Cedara Agric. Res. Stn, Kwazulu-Natal, RSA
38. 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
Brazil 17.3 Ghana: 100.000 small
farmers use NT
Paraguay 1.3
Argentina 11.7 Australia
9.0
Based on Derpsch 2002
39. Farmers Perceptions of the Benefits of
Conservation Agriculture
Perceived by:
Benefit Large Farmers Small Farmers
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 +++ + (+++) a
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.
40. The principles of conservation
agriculture appear to have
extremely wide application
The actual formulae and
technologies for applying these
principles are very site-specific.
