Surface Roughening and Maintaining Stable Aggregates

John Tatarko Author

04/08/2019 Added

252 Plays

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This video clip explains how wind erosion can be reduced by roughening the soil surface and forming soil aggregates. This method of erosion control can be used when vegetation is sparse and/or the cropping system does not allow for vegetative cover.

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[00:00:01.080]As a result of drought or some cropping practices or crop types,
[00:00:05.046]ridges and large soil clods or aggregates are frequently the only means of
[00:00:09.624]controlling erosion on large areas.
[00:00:12.440]Roughening the land surface with ridges and clods reduces the wind velocity and
[00:00:17.192]traps drifting soils.
[00:00:19.760]While a cloddy soil surface will absorb more wind energy than a flat,
[00:00:24.141]smooth surface, a soil surface that is both ridged and
[00:00:27.584]cloddy will absorb even more.
[00:00:30.760]Soil crust can also increase resistance of the surface soil to wind forces,
[00:00:35.282]but this effect is only temporary and should not be relied upon for erosion
[00:00:39.804]control.
[00:00:43.880]Cross wind ridges are formed by tilling or planting across the prevailing wind
[00:00:48.571]erosion direction.
[00:00:50.000]If erosive winds show no seasonal or annual prevailing direction,
[00:00:53.864]this practice has limited protective value.
[00:00:57.640]Tillage implements can form ridges and depressions that alter wind velocity.
[00:01:02.400]The depressions also trap saltating soil particles and stop avalanching of eroding
[00:01:07.133]material downwind.
[00:01:08.680]However, soil ridges protrude higher into the
[00:01:11.276]turbulent wind layer and are subject to greater wind forces.
[00:01:15.160]Therefore, it is important that cloddiness on top of
[00:01:18.150]the ridge is sufficient to withstand the added wind force.
[00:01:21.800]Otherwise, they will quickly erode and the
[00:01:23.864]beneficial effects will be lost.
[00:01:26.120]Ridging sandy soils, for example, is of little value because the ridges of
[00:01:30.485]sand are erodible and soon leveled by the wind.
[00:01:35.840]Clod forming tillage produces aggregates or clods that are large enough to resist
[00:01:40.649]the wind force and traps smaller moving particles.
[00:01:44.240]They are also stable enough to resist breakdown by abrasion throughout the wind
[00:01:48.181]erosion season.
[00:01:50.640]If clods are large and stable enough, as smaller particles are removed or
[00:01:54.874]trapped, the surface becomes stable or armored
[00:01:57.563]against erosive action.
[00:01:59.320]The duration of protection depends on the resistance of the clods to abrasion or
[00:02:03.610]changes in the wind direction.
[00:02:09.360]Of the factors that affect the size and stability of soil aggregates,
[00:02:13.545]most notable is soil texture.
[00:02:15.720]Sandy or coarse textured soils lack sufficient amounts of silt and clay to
[00:02:20.358]bind particles together to form aggregates.
[00:02:24.160]Such soils form a single grain structure or weakly cemented clods,
[00:02:27.954]a condition that is quite susceptible to erosion by wind.
[00:02:34.160]Many other factors also affect aggregate consolidation and stability climate,
[00:02:40.973]including moisture compaction, organic matter,
[00:02:45.078]lime microorganism activity, and other cementing materials.
[00:02:53.160]Any process that reduces soil consolidation also increases erodibility.
[00:03:00.240]The persistence of aggregates is greatly affected by the climatic processes of
[00:03:04.837]wetting and drying, freezing and thawing, or freeze drying,
[00:03:08.329]which generally disintegrate clods and increase erodibility.
[00:03:13.160]Mechanical action such as tillage, animal or machine traffic,
[00:03:16.813]and abrasion by saltating soil particles can also affect cloudiness.
[00:03:21.360]Tillage may either increase or decrease clods at the surface,
[00:03:24.564]depending on the soil condition in the tilled layer and the type and speed of
[00:03:28.596]the implement.
[00:03:29.880]Repeated tillage usually pulverizes and smooths dry soils and increases their
[00:03:34.886]erodibility, especially if done with implements that
[00:03:38.288]have an intensive mechanical action such as tandem disks, offset disks, or harrows.
[00:03:45.520]Soil water at the time of tillage also has a decided effect on cloudiness.
[00:03:49.960]Research has found that different soils have differing water contents at which
[00:03:54.546]soil pulverization is most severe.
[00:03:57.800]Smaller clods are produced if the soil is either extremely dry or extremely moist
[00:04:03.081]than at intermediate water contents.

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Surface Roughening and Maintaining Stable Aggregates

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