1. Purpose of Tillage
“The main purposes of tillage are to prepare a seedbed, to prepare a rootbed, and to eliminate competing vegetation.”

2. Kinds of Tillage
Conventional Tillage: Moldboard plowing followed by one or more passes with a secondary tillage implement, such as a disk, field cultivator, or other finishing tool.
Primary tillage: Moldboard Plow:
Advantages: Lifts, turns, aerates, and loosens the soil and incorporates organic matter. Does not compact the soil when used properly
Disadvantages: Increases likelihood of both wind and water erosion, creates a plow pan if plowed at the same depth each time, decreases infiltration rate after first significant rain (crust formation).

3. Kinds of Tillage Conventional Tillage (contd.)
Secondary Tillage: Usually includes the use of a tandem disc, field cultivator, or some other type of combination finishing tool to smooth the soil surface.
Used to break-up lumps and clods from primary tillage pass
Incorporates residues that improve soil tilth
Can over-till, breaking the soil into fine particles that
enhances crusting and decreasing soil infiltration
Increases the chance of both wind and water erosion
Tools, such as tandem discs, can pack the soil below the cutting depth as a result of their weight.

4. Kinds of Tillage
Conservation Tillage: “Any tillage and planting system that maintains at least 30% of the soil surface covered by residue after planting to reduce soil erosion by water” (Soil Conservation Service).
No-till/Strip Till: Managing the amount, orientation, and distribution of crop residue and other plant residue on the soil surface year-round, while growing crops in narrow slots or tilled, or residue free strips in soil previously untilled by full width inversion implements.
Mulch Till: Managing the amount, orientation, and timing of crop residue year round while growing crops where the entire field surface is tilled before planting.
Ridge Till: Managing the amount, orientation, and timing of crop residue year-round while growing crops on preformed ridges alternated with furrows protected by crop residues.

5. Residue Cover and Erosion Potential
Tillage System
Residue Cover
Erosion Potential
Conventional (clean)
None
High
Reduced
15 to 30%
Moderate to High
Mulch
30% or more
Low while soil is mulched
Strip
Low where mulch remains No
30% or more (year-round)
Low

6. Typical Field Operations
System
Typical field operations
Major Advantages
Major disadvantages
Moldboard plow
Fall or spring plow; one or two spring diskings or field cultivations; plant; cultivate
Suited to most soil and management conditions. Suitable for poorly drained soils. Excellent incorporation. Soils warm up early.
Excessive soil erosion. High soil moisture loss. Must be timed carefully. Highest fuel and labor cost.
Chisel plow
Fall chisel; one or two spring diskings or field cultivaitons; plant; cultivate.
Less erosion potential than fall plow or fall disk. Well adapted to all soils, including those that are poorly drained. Good to excellent incorporation.
Multiple passes cause excessive soil erosion and moisture loss. In heavy residues, may need to shred stalks to keep chisels from clogging.
Disk
Fall or spring disk; spring disk and/or field cultivate; plant; cultivate.
Less erosion than from cleanly tilled systems. Well adapted for lighter-to-medium textured, well-drained soils. Good-to-excellent incorporation
Multiple passes cause excessive soil erosion and moisture loss. Disking wet fields compacts the soil.
Source: Management of Wisconsin Soils, University of Wisconsin, Extension, pg.33.

7. Typical Field Operations contd.
System
Typical field operations
Major Advantages
Major disadvantages
No-till
Spray; plant into undisturbed surface; postemergent spray as necessary.
Maximum erosion control. Soil moisture conservation. Lowest fuel and labor costs.
No incorporation. Increases dependence on herbicides. Not well suited for poorly drained soils.
Ridge-till
Shred stalks; plant on ridges; cutlivate for weed control and to rebuild ridges
Excellent erosion control on contour fields. Well adapted to all soils. Ridges warm up and dry out quickly. Low fuel and labor costs.
No incorporation. May be difficult to create and maintain ridges. Not well suited to narrow-row corn or soybeans.
Source: Management of Wisconsin Soils, University of Wisconsin, Extension, pg.33.

8. Comparison of Tillage Systems
Conventional
Advantages: Suited to most soil and management conditions. Suitable for poorly drained soils. Excellent incorporation. Soils warm early.
Disadvantages: Excessive soil erosion. High soil moisture loss. Must be timed carefully. Highest fuel and labor costs

9. Comparison of Tillage Systems
No-Till
Advantages: Minimize soil erosion. Soil moisture conservation. Lowest fuel and labor costs.
Disadvantages: No incorporation. Increases dependence on herbicides. Not well suited for poorly drained soils.

10. Purpose of Conservation Tillage
Six purposes can describe the reason to adopt a conservation tillage system:
Reduces sheet and rill erosion
Reduces wind erosion
Maintains or improves soil organic matter content
Conserves soil moisture
Manages snow to increase plant available moisture
Provides food and escape cover for wildlife

11. Soil Tillage Soil crusting Associated with tillage and residue removal
Raindrops dislodge sand, silt, clay, and O.M. particles from the soil aggregates
Sand to bottom, silt in middle, clay on surface forming a crust
Crop residues on surface minimize crust formation
Most clay soils will shrink enough upon drying to break up crusts
Silt loam soils low in organic matter seem to produce the heaviest crusts.

12. Tillage and Residue Management
Clean till vs.. high surface residue impacts:
Soil temperature: High surface residues tends to hold soil moisture. Soils with high surface residue and moisture content warm more slowly in the spring.
Soil erosion: High surface residue breaks the impact of rain droplets and protects the surface soil from high wind velocity. Soils are most vulnerable to erosion following a tillage pass that destroys residue cover.

13. Tillage and Residue Management
Clean till vs.. high surface residue impacts:
Soil moisture: High surface residues generally increase water infiltration and minimize evaporative losses, making soils covered with residues with more soil water.
Organic Matter: Soil organic matter will decrease over time under conventional “clean tillage”. Organic matter may slightly increase over time with the adoption of reduced or no-tillage systems.

14. Corn Residue Remaining After Tillage
Management of Wisconsin Soils, pg. 31

15. Crop Residue After Harvest
Pounds Residue/Bu Yield
Wheat
100
Barley 80
Oats 55
Rye
Soybeans 50
Corn 60
Sorghum
Crop residue management strategies should begin at harvest-time. The amont of residue that remains in the field is a combination of the crop, crop yield, and row spacing. The relationship between % crop residue and dry matter yield is best described as a quadratic relationship, % residue increases as dry matter yield increases, but to a lesser extent as yields go up.
Most producers will not know how much dry matter a crop produces, but they will usually know their per acre yield. You can use the factors in this table to help make a residue estimation when used in combination with the following figure showing the relationship between pounds of residue and % residue cover.
Source: Managing Crop Residue From Harvest to Planting, Peter Hill, in Crop Residue Management To Reduce Erosion and Improve Soil Quality, USDA, ARS, Conservation Research Report Number 42, November, 1995.

16. Over-winter Decomposition Rates
Non-fragile
Alfalfa or legume hay
Barley
Buckwheat
Corn (grain, forage, silage)
Grass hay
Millet
Oats
Pasture
Popcorn
Sorghum
Wheat
Fragile
Canola/rapeseed
Dry beans
Dry peas
Fall-seeded cover crops
Mint
Potatoes
Soybeans
Sugar beets
Sunflowers
Most vegetables
Decomposition of crop residue over the winter months is a function of several factors, including rainfall, temperature, and prior disturbance. Decomposition will vary among crops, depending the integrity of the residue. Crops have been divided as non-fragile and fragile to help differentiate the ability of the residue to withstand degradation over the winter months. Non-fragile crops, like corn, usually have large leaves or stalks that produce large quantities of biomass. Fragile crops produce a substantially less amount of crop residue per unit yield. If crop residue is disturbed by fall tillage or by knifing in fertilizer, the decompositiojn rates will likely be higher than if left undisturbed. Decomposition proceeds quickly when temperatures are above 500 F and adequate moisture is available.

17. Percent of Residue Remaining Following Different Operations
Finishing Tools
Rotary Tillers
Row Cultivators
Unclassified Operations
Drills
Row Planters
Overwinter Weathering (harvest)
Plows
Machines That Fracture Soil
Chisel Plows
Combination Chisel Plows
Disk Harrows
Field Cultivators

18. Estimating Residue Cover
Soil erosion can be substantially reduced by keeping a residue cover on the soil surface. As little as 30% surface coverage (measured after planting) can reduce soil surface erosion by 65% (see following table)
Many farmers have chosen conservation tillage as part of their conservation compliance plan.
Residue can be measured using a variety of methods including photographic, meter stick, and line-transect, with the line-transect emerging as the preferred method.

19. Residue and Erosion Reduction
Residue Cover
(% on any day)
Erosion Reduction %
(while residue present) 10 30 20 50 65 40 75 83 60 88 70 91 80 94
Source: Core4 Conservation Practices and Training, Chapter 2, pg. 3

20. Estimating Residue Cover Line Transect Method
Equipment
Knotted rope or tape measure
Wire cable, with beads or tabs
Line should be
100 feet long with markings at 1-foot intervals
50 feet long with markings at 6-inch intervals
Each time the line is stretched and residue recorded, it will provide an evaluation at points.
Attach a stake at one end of the rope, tape, or cable.

21. Line Transect Method
Stretch the rope across a field or tillage pass diagonally
Count the number of marks that have residue directly under the leading edge of the mark. Sight from directly above the mark.
Residue pieces must be greater than 1/8-inch diameter to count
Residue pieces must touch or be under a knot to count
Total number of knots with residue under them is the percent residue cover
Take at least three measurements from representative locations in different areas of the field. Average the measurements.

22. Photo Comparison Method
Corn Residue
10%
50%
30%
90%
Residue cover can also be estimated by comparing actual field conditions to photographs of known percentages of cover This method provides a quick estimate, but is less accurate than the line-transect.
Go to a site typical of the field, look straight down, and compare what you see with what the photographs show; then estimate your percentage of residue cover based on that comparison. Repeat the procedure at four other typical sites, and average your estimates.
Scanning from the road or field boundary doe not provide an adequate evaluation.
Soybean Residue
10%
30%
40%
80%
Source: Purdue University Agronomy Guide AY-269

23. Restrictive Zones Surface compaction Subsurface compaction Crusting
Naturally-occurring layers

24. Restrictive Zones Surface Compaction
Associated with spring field preparation and too wet soil conditions
Wheel track compaction: Under vehicle and implement tires or tracks.
Tillage-induced compaction: Occurs at the depth that the tillage tool works the soil.
Zone affected is not greater than 6 inches
Tillage, freeze/thaw cycles and wet/dry cycles break-up surface compaction

25. Surface Compaction Plant Growth
Shallower-than-expected planting depth
Poor seedling emergence
Increased chemical injury
Anaerobic environment not conducive to root growth

26. Surface Compaction Plant Growth
Surface compaction can be minimized or prevented by:
Do not work wet soils
Keep axle loads as low as possible
Reduce the number of trips over the field
Follow the same wheel track when possible
Increase organic matter residue at the surface

27. Restrictive Soil Layers Subsurface Compaction
Dense zones
Begins at the bottom of the tillage zone
The layer need not be thick to have a large negative impact on plant growth (1 to 2 inches)
Often associated with fall harvest axle loads over 5 tons, and wet soil conditions
Tillage in some cases may actually aggravate the condition by breaking down soil aggregates.

28. Subsurface Compaction Plant Growth
Reduces infiltration and allows water to saturate soil (enhancing environment for nitrogen loss)
Lack of available soil air (O2) for root uptake
Increased disease risk
Causes shallow rooted plants and may limit above-ground growth

29. Subsurface Compaction Plant Growth
Subsurface compaction can be minimized or prevented by:
Keeping axle loads as low as possible (grain carts)
Reducing the number of trips over the field
Following the same wheel track where possible
Stay off wet fields
Vary tillage depth
Deep rip

30. Restrictive Soil Layers Crusting
Rain impact and splash
Particularly on fine-textured soils
Breakdown soil aggregates
Fill pore spaces
Reduce air exchange
Lack of adequate surface coverage is a primary contributor to the problem

31. Crusting Plant Growth Crusting Physically impedes seedling emergence
How to minimize crusting
Rotary hoeing
Cultivating
Increasing soil residue so it does not occur in the first place

32. Restrictive Soil Layers Naturally Occurring Zones
Hardpans
Fragipans
Claypans
Caliche
Caused by:
Sodium or very high levels of calcium
High sodium soils typical of Western soils
High calcium soils typical of Midwest soils
Oil wells and some bi-products

33. Restrictive Soil Layers Naturally Occurring Zones
Management Options
Very deep tillage may help
Divert water source through tile
Deep-rooted trap crops
Gypsum may have some benefit on the high sodium soils

34. Definitions
Caliche: A zone near the surface, more or less cemented by secondary carbonates of Ca or Mg precipitated from the soil solution. It may occur as a soft thin soil horizon, as a hard thick bed, or as a surface layer exposed by erosion.
Claypan: A dense, compact, slowly permeable layer in the subsoil having a much higher clay content than the overlying material, from which it is separated by a sharply defined boundary. Claypans are usually hard when dry, and plastic and sticky when wet.

35. Definitions
Fragipan: A natural subsurface horizon with very low organic matter, high bulk density and/or high mechanical strength relative to overlying and underlying horizons; has hard or very hard consistence (seemingly cemented) when dry, but showing a moderate-to-weak brittleness when moist. The layer typically has redoximorphic features, is slowly or very slowly permeable to water, is considered to be root restricting, and usually has few-to-many bleached, roughly vertical planes which are faces or coarse or very coarse polyhedrons or prisms.

36. Definitions
Hardpan: A soil layer with physical characteristics that limit root penetration and restrict water movement.
Redoximorphic features: Soil properties associated with wetness that result from the reduction and oxidation of iron and manganese compounds in the soil after saturation with water and desaturation, respectively.