Field Crop Production
Non-tillage Options

Conservation Structures for Cropland

Tile Drainage and Water Table Management

Good land drainage is necessary for all farm operations. There is no question about the value of tile drainage to farm production on some soils. It will increase the yield of most crops and improve the efficiency of the overall operation by artificially removing excess water from soil.

Subsurface drainage is an important conservation practice. It can reduce surface run-off during some seasons by allowing more water to soak into the soil.

In the past, underground tiles were installed simply to remove excess water from soil. Recently, however, research shows these drains may also serve as a water supply or irrigation system. By regulating water flow in the drains, groundwater levels are maintained near the bottom of the crop root zone. Good soil moisture levels result in increased crop production.

In the United States this is now an accepted best management practice. Nutrients and chemicals are used more efficiently by the crop rather than being released out of a tile drain.

Terraces

Terraces reduce erosion by controlling and managing surface run-off. A terrace is a channel with a supporting downslope ridge constructed across the slope. Terraces break up long slopes into a series of short ones with each one collecting excess water from an area above it. The collected water is then removed from the field safely.

Terraces are the most expensive conservation practice. However, they allow for more intensive row cropping while keeping erosion in check. Studies in the United States show crop yields on terraced land are 10-15% higher than those on erodible land that is not terraced. Full recovery of construction costs can occur in as little as three years.

Terraces make more economic sense when combined with other conservation practices such as contouring, strip cropping, or conservation tillage.

Steepness of slope, soil erodibility, crop type, management and rainfall, all determine terrace spacing. Adjustments are then allowed for matching equipment dimensions and fitting the topography better. Where more than one terrace is planned, care must be taken to ensure the ridges are parallel.

Suitable outlets for the collected water behind the terrace include either vertical pipe intakes outletting into tile drains, or grass waterways. Conservation tillage and contouring are necessary to maintain terrace systems.

There are three choices to Terrace Design: Broad Base, Grass Backslope and Narrow Base.

Broad Base

The entire terrace is farmed; it is restricted to field slopes under 8%. Care must be taken not to work down the ridges during field operations. Costs are twice that of narrow base terraces.

Grass Backslope

Suited to steeper land, the backslope is seeded to permanent vegetation.

Narrow Base

Both front and back slopes are steep and seeded to permanent vegetation. Using bulldozers to construct, the costs should be less than $2.25/ft (1991) to complete.

Properly designed and installed inlets make tile outlet terraces successful. They must be kept clear of debris for efficient operation.

Terraces are a big investment, but they provide a farmer with more options in planning a cropping system. Terraces must be built right and maintained. It is a good idea to get experienced help to plan a terrace system.

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Water and Sediment Control Basin

These structures are built across drainage ways and work like small dams. They intercept concentrated run-off temporarily and release it through a tile drain. Relatively inexpensive to install, these terraces will complement a conservation management system on land with irregular and non-uniform slopes.

Diversion Terrace

A diversion is a channel with a supporting ridge on the lower side, constructed across the slope to intercept surface run-off, carrying it safely to an outlet. Use this system where land cannot be terraced because of topography or because it belongs to someone else. Diversions will carry substantial amounts of water and should be permanently vegetated.

Grass Waterways

Grass waterways are broad, shallow channels protected against erosion by grass cover. They serve as outlets for terraces, diversions, contour rows or as passageways for surface flows entering the farm from other land.

Water will often collect along natural depressions in the field and run off. This is common to almost every farm. The success of a soil conservation program often requires a well-maintained grass waterway. Modern equipment will cross a grass waterway without difficulty.

Grass waterways must be wide and deep enough to handle all rains without damage. They must also be shaped to allow easy crossings by farm machinery. Crop rows should always enter the waterway at right angles.

The waterway must be well-drained to encourage vigourous grass growth and to protect the waterway from rutting when farm machinery crosses it. Tile drains can be installed along one, or both sides. A surface inlet may be installed at the upper end of the waterway to intercept long-running, overland water flow.

Occasionally, grade control is required to maintain the waterway through steep slopes. Irregular-shaped rock over a filter cloth is the most commonly used material.

Available in Published Version of Field Crop Production

• Terraces
  • Recommended Terrace Spacing with and without a Conservation Management System - Chart

Non-tillage Options cont'd.

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