Rolland Z. Wheaton and Edwin J Monke, Agricultural engineering Department, college Indiana farmers have long well-known the prestige of controllingsoil erosion and the benefits of using conservation measures. Foryears, the an easy motivation behind their conservation efforts was "tomaintain the soils resource in a highly abundant state." back that"s reason sufficient to usage sound land administration practices, this day farmers have second `motive"--compliance v the national Clean Water Act, which seeks to eliminate the contamination of streams, rivers and lakes by any type of source, including runoff from agricultural land. The regulation specifies that manage of nonpoint-source pollution is tobe achieved primarily by applications of `best managementpractices." BMPs are those conservation steps and/or landmanagement approaches deemed most efficient in staying clear of pollution byrunoff or seepage indigenous a given field or floor area right into watercourses. One BMP applicable to some of the cropland the Indiana isterracing. This publication looks for to answer the commonly-askedquestions about terraces, including: what are the various types?,how do they work?, where space they most effective (or ineffective)?,what does it take to construct and also maintain them?, and where does oneget assist with design, installation and also financing? indigenous the informationpresented, hopefully farmer can better assess the potential worth ofthis BMP come their particular situations.

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What is terracing?

Terracing is a soil conservation practice applied to preventrainfall runoff on sloping land native accumulating and causing seriouserosion. Terraces consist of ridges and channels constructedacross-the-slope.

What varieties of terraces space there, and also how perform they differ?

To some people, words `terrace" brings to mind bench terracesthat are provided in miscellaneous mountainous areas of the world. Much more often,one pictures contour terraces, v their point rows and also grassedwaterway outlets, that follow the lay-of-the-land (Figure 1).
Figure 1. A edge terrace mechanism with many allude rows and also grassedwaterways. Today, however, the type most common on farming land in theU.S. Space parallel terraces, therefore named due to the fact that they areconstructed parallel come each various other and, wherein possible, to thedirection of ar operations (Figure 2). Parallel terraces eliminatethe production losses linked with point rows and also minimizeinterference to farming operations when spaced at multiple widths ofplanting and harvesting equipment.
Figure 2. A parallel terrace system. Some terraces are created with steep backslopes that are keptin grass. Most, however, space broad-based having actually gently sloped ridgesthat are cultivated as a part of the field. In semi-arid areas (e.g., west Kansas and Nebraska), contourterraces may have actually level networks to collect and also hold the water untilit seeps right into the soil. In humid regions prefer Indiana, many terraceswill have graded channels that convey the water come an outlet. Terraces that are created in parallel and also discharging runoffthrough subsurface drains are known as parallel brick outletterraces. With PTO terraces, water that accumulates behind aterrace ridge is discharged v a surface ar inlet right into a subsurfacedrain. The surface ar inlet, dubbed a riser, has actually a restricted section tocontrol the discharge rate, bring about some of the runoff come betemporarily save on computer (Figure 3). This storage duration is long sufficient forsediment to resolve out the the water, however not for this reason long regarding damage thecrop.
Figure 3. Water temporarily stored behind a newly constructed PTOterrace.

What space the services of a terrace system?

The significant benefit, the course, is the conservation of soil andwater. Terraces minimize both the amount and also velocity the water movingacross the floor surface, which considerably reduces soil erosion. Terracingthus permits an ext intensive cropping than would otherwise be possible. PTO terraces carry out these included benefits: (1) the total area canbe farmed, because grassed waterways are not needed; (2) elimination ofgrassed waterways likewise eliminates the inconvenience they cause whentilling or using herbicides; (3) optimal discharges space reducedbecause runoff is in the interim stored; and (4) sediment and othercontaminants resolve out behind the terrace ridge prior to pollutingwater in a receiving stream.

To what field conditions are terraces ideal adapted?

fields with long, fairly-uniform slopes that room not too steep(generally much less than 8 percent) are best adapted to broad-basedterraces. If the slopes are very irregular or if the soil is shallow(less than 6 inches), alternate BMPs should most likely be used. The overall slope the a ar being terraced can be improved bytaking fill material from the `right" areas in that field. Topsoilshould be gotten rid of from both the cut and the to fill areas and stockpiled,especially v shallow soil. It can later be spread back over theterrace and borrow areas. In some cases, top top land whereby a total terrace mechanism is notpractical, terraces are occasionally placed across minorwatercourses. This kind of terrace supplies subsurface outlets comparable toPTO terraces. That controls sediment discharge however doesnot check soil erosion as effectively, since steepslopes are most likely to exist over the terrace.

How reliable are terraces in managing erosion?

Generally, very effective! they intercept rainfall runoff together itstarts down a slope, thus avoiding a large accumulation of flow onthe surface. This reduce the potential for sheet and also rill erosion. In effect, terraces break up one lengthy slope into a number of shortones. As already mentioned, PTO terraces likewise give soil particles thatdo erode a chance to settle out in the container behind the terrace ridge,while the overfill water is progressively discharged v a subsurfacedrain.

To what level do terraces interfere with field operations?

any permanently-installed exercise will, to part degree, obstructfield work and/or take part land the end of production. However,these obstructions are considerably minimized under existing methods ofdesign. Because that instance, through a PTO terrace system, elimination of thegrassed waterways an ext than offsets the interference resulted in bycross-slope ridges and channels.

Does terracing require alters in tillage practices?

because terraces are constructed across the slope, tillage will certainly alsobe excellent in the direction. Cross-slope tillage may be the onlyadditional adjust needed. However, usage of preservation tillagepractices additionally might permit higher distances between terraces.

Can (or should) i install terraces myself?

some terrace systems deserve to be built using standard farmequipment, such as a moldboard plow. Much more often, however,bulldozers, engine patrols (graders) and towed or self-propelledscrapers room needed. If earth must be moved a substantial distance, ascraper is more than likely best. Aside from equipment availability, another consideration in thedecision to do-it-yourself is the farmer"s time commitment andknow-how. Because that many, it"s wisest to hire an proficient land contractorto perform the job. Nevertheless of that installs it, a terrace system must be welldesigned. Terraces need to be spaced correctly, have actually adequate ridgeheight and also channel cut to administer the essential water storage, andhave properly-sized outlets. Substantial field surveying work may beneeded to design and also stake the end a system. Usually this will call for theservices of an engineer or someone specially trained in terracedesign.

Must the task be excellent at one time?

It"s ideal if that is however doesn"t have to be. By beginning at the topand working downhill, building of a terrace system can be spreadover more than one season. A diversion might be needed at the upper edge the the field, if anuncontrolled runoff area exists above it. The water outlet have to beinstalled the year before terrace building begins.

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What form of maintenance is required?

The key thing is annual preventive maintenance, such together removingdebris indigenous outlets and also smoothing out silt bars in thechannels. However, yearly tillage activity will at some point wear downthe terrace ridges, requiring that they it is in rebuilt occasionally. Thisis done by plowing toward the ridge height from both sides through amoldboard plow. The use of conservation tillage techniques is a goodmeans that assuring lengthy life for a terrace system.

Where deserve to one go for further information or assistance?

For much more detailed info on terracing and for assist in assessing its potential together a BMP on a offered farm, contact the participating Service farming Educator or U.S. Herbal Resources Conservation service conservationist in ~ your neighborhood county seat. Technical aid in the design and layout the terrace equipment is available from the herbal Resources Conservation organization through the local Soil and also Water preservation District. 6/81REVIEWED 4/01
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