Conservation Tillage

1
Conservation Tillage
2
Conservation Tillage

• portion of previous crop residue left
  unincorporated on soil surface

3
Conservation Tillage

• portion of previous crop residue left
  unincorporated on soil surface
• Opposite of conventional tillage (plowing)
• Plowing benefits good root zone, weed management
• Not plowing benefits erosion management

4
Tillage Options

• Tillage (turn in everything)
• Top mowed and removed (root stubble left)
• Top mowed, but left as mulch (root stubble left)
• Planting into dead crop residues (nothing removed)

5
Tillage and Crop Residue Management
100
NONE
SURFACE RESIDUE
TILLAGE INTENSITY
FREQUENT
0
6
Tillage and Crop Residue Management
100
NONE
No tillage
SURFACE RESIDUE
TILLAGE INTENSITY
Minimum tillage Reduced tillage
FREQUENT
0
7
Tillage and Crop Residue Management
100
NONE
No Tillage 90
SURFACE RESIDUE
TILLAGE INTENSITY
30 Minimum Tillage
FREQUENT
0
8
Conservation Tillage

• portion of previous crop residue left
  unincorporated on soil surface
• Many different terms
• Reduced Tillage
• No Tillage
• Minimum Tillage
• Crop Residue Management

9
Conservation Tillage

• Reduced Tillage
• No Tillage
• Minimum Tillage
• Crop Residue Management
• Many different terms, depending on relative
  amounts of residues and varying degrees of
  incorporation (cover crop mowed and used as
  mulch, forage removed with stubble left in field,
  etc.)

10
Strip Tillage

• Crops planted into narrow tilled strip (4-12,
  10-30 cm)

Residue on surface
Residue on surface
11
Strip Tillage Planting into Crop Residue
12
Rye Cover Crop Killed by Herbicide, Use Strip
Till Planter to Plant Crops
13
Crops Strip Planted into Green Cover Crop, Cover
Killed Later with Herbicide
14
Strip Till Peanut in Rye Mulch (double row)
15
Strip Till Peanut in Rye Mulch (single row)
16
Strip Till Corn in Rye Mulch
17
Strip Till Cotton in Rye Mulch
18
Conservation tillage in US increased rapidly
since 1980s
Schertz, 1994
19
Advantages and Reasons for using Minimum Tillage

• Reduced erosion
• Economics
• Moisture conservation
• Stabilizes soil temperature
• Improved soil fertility and accessibility
• Improved quality of surface water
• Government regulations and programs
• Improved yields

20
Relationship between Conservation Tillage (more
surface residue) and Reduction in Erosion
21
Advantages and Reasons for using Minimum Tillage

• Reduced erosion
• Economics (reduced trips over field and fuel
  costs, but more herbicide)
• Moisture conservation (reduced evaporation rates)
• Stabilizes soil temperature
• Improved soil fertility and accessibility
• Improved quality of surface water
• Government regulations and programs
• Improved yields

22
Relationship between Conservation Tillage (more
surface residue) and Moisture Conservation (less
evaporation)
23
Advantages and Reasons for using Minimum Tillage

• Reduced erosion
• Economics
• Moisture conservation
• Stabilizes soil temperature
• Improved soil fertility and accessibility
  (preserves OM)
• Improved quality of surface water (reduced
  erosion and runoff)
• Government regulations and programs
• Improved yields

24
Advantages and Reasons for using Minimum Tillage

• Reduced erosion
• Economics
• Moisture conservation
• Stabilizes soil temperature
• Improved soil fertility and accessibility
• Improved quality of surface water
• Government regulations and programs (Food
  Security Act 1985 Minimum tillage considered
  part of soil conservation program to reduce
  erosion)
• Improved yields

25
Advantages and Reasons for using Minimum Tillage

• Reduced erosion
• Economics
• Moisture conservation
• Stabilizes soil temperature
• Improved soil fertility and accessibility
• Improved quality of surface water
• Government regulations and programs
• Improved yields ? --- Depends on soil types and
  conditions.

26
Soybean Yield (bu/A)
Benefit from no-till in poor soils
From Johnson, 1994
27
Improved Yields from Minimum Tillage?

• South US, dry soils greater yields
• North US lower yields (cooler temps.,
  less DD in no-till)

28
Problems with Minimum Tillage

• Weeds
• Weed pressure often severe in min. tillage
• Increased herbicide usage for weed control and
  for killing crop residues
• Roundup-Ready cultivars
• New weed problems K strategists, etc.
• Compaction -- varies

29
US Pesticide Sales following Increase in
Conservation Tillage
Mostly herbicides
Johnson, 1994
30
Effects of minimum tillage on physical and
biological factors

• Soil moisture
• Soil temperature
• Soil fertility
• Soil acidity
• Pests

31
Effects of minimum tillage Soil Moisture

• Decreased evaporation and water loss
• improved water holding capacity on soils that
  tend to dry
• - - may delay drying in water-logged soils

32
Effects of minimum tillageSoil Temperature

• Lowers soil temperature, depending on amount of
  residue
• for South US, tropics
• - - for north (soil warming may be delayed in
  spring)

33
Effects of minimum tillageSoil Fertility

• increased organic matter, reduced erosion
• - - N availability can be affected by residues
  and lead to deficiency

Fertilizer placement and degree of incorporation
is important CN ratio of residue is
critical Placement important with other
nutrients (P, K) too
34
Effects of minimum tillageSoil Fertility

• increased organic matter, reduced erosion
• - - N availability can be affected by residues
  and lead to deficiency

Fertilizer placement and degree of incorporation
is important CN ratio of residue is
critical Placement important with other nutrients
(P, K) too
Strip Tillage can help with these fertilizer
placement problems !
35
Effects of minimum tillageSoil Acidity

• Can increase with decomposition and organic acids
• Can affect nutrient availability
• Takes time to develop and may be confined in a
  relatively narrow vertical strip

36
Effects of minimum tillage Pests

• Weeds --- can be major problem
• Diseases
• Insects

37
Effects of minimum tillage Diseases

• Varies with specific situations and ecology of
  pathogens
• Crop rotation important to eliminate residues of
  the same crop (contaminated residues could be
  source of disease inoculum)
• Some seed pathogens worse with cooler soil
  temperatures

38
Effects of minimum tillage Insects

• Varies --- may favor pests or beneficials
• Favorable habitat and hiding places for crop
  pests in residues (cutworms, snails, slugs)
• May provide habitat for predators

39
Tillage impacts larger organismsNo tillage
benefits earthworms, predators
Coleman and Crossley, 1996
40
Seedbed Problems in Min. Tillage

• Problem in cool, moist soils
• Increased seedling mortality from
• Mulch layers
• Diseases (aggravated by cool temp. and moisture)
• Slow germination and establishment (lower DD if
  soil is cool)

41
References

• Text, Ch. 14, pp. 287-295.
• Altieri, 1987. Ch. 11.
• Coleman, D.C., and D.A. Crossley. 1996.
  Fundamentals of Soil Ecology. Academic Press, San
  Diego.
• Johnson, R.R. 1994. Pp. 12-22 in P.J. Bauer and
  W.J. Busscher, eds. Proc. of the 1994 Southern
  Conservation Tillage Conference for Sustainable
  Agriculture. USDA Coastal Plains Soil, Water, and
  Plant Research Center, Florence, SC.
• Schertz, D.L. 1994. Pp. 1-5 in Bauer and Busscher.