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

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).

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.

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.

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

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.

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.

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

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.

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

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.

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.

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.

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

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.

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.

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

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.

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

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 100 points. Attach a stake at one end of the rope, tape, or cable.

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.

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

Restrictive Zones Surface compaction Subsurface compaction Crusting Naturally-occurring layers

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

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

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

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.

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

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

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

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

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

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

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.

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.

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.