Environmental Issues/Problems
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Land and Soil Drainage (Tour Map Symbol 'D')
General Problems
Some eastern South Dakota soils do not have very good internal drainage because of their lower position on the landscape or because of their high clay content. In addition, the surface drainage of some areas of eastern South Dakota, especially in the "Prairie Coteau" is not well developed since glacial activity filled and blocked ancestral drainage patterns and permanently rearranged the landscape. During a recent wet period (1993-1998), surface water in streams and rivers swallowed up good farmland and extended the drying period beyond the planting date of most crops. Moisture from heavy rains drained into the lowest parts of the landscape and swelled the size of the glacier lakes (prairie potholes). This blocked obstructed many secondary and gravel roads and delayed agricultural operations significantly.
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Drainage Solutions
a.Tile Drain Installation
Installing an underground drainage system (tile drainage) with perforated pipe is a costly but effective solution for improving drainage on a landscape scale. However, federal legislation in the mid-1980's (also called "Swampbuster Legislation") restricts some aspects of installing tile drains. recently, some of these regulations have been loosened a bit. Local water conservation districts and a good neighbor policy often are involved in granting tile drain permits and successful installations.
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b. No Till Practices
Farmers have also found that reducing tillage or "no-tilling" fields on level ground has improved their internal drainage. Planting operations can begin a few days earlier in untilled ground after a soaking rain compared to fields which are extensively tilled. After many years of no-till agriculture, the residual organic materials form aggregates with the soil which improves the internal drainage of the surface soils. Tillage would destroy many of these aggregates and would lead to incomplete drainage. In addition, roots from former crops and burrows out tunnels from Meso Fance act as channels as they are decomposing and can move surface water to deeper depths. Tillage would destroy many of the soil aggregates in the top soil, and disrupt the continuity of old root channels for moving water through the soil profile.
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Soil Erosion (Tour Map Symbol 'Ep')
General Problems
Soils on landscapes which are moderately or relatively steep are most sensitive to water erosion. Tillage intensifies the erosion potential since it loosens the soil and not as much energy is required to move the soil form it's placement position. Wind erosion is also a problem in eastern South Dakota, although less than it used to be. Generally most wind erosion occurs in the spring or the fall when the freshly tilled soil is exposed to drying forces of the nearly constant wind. Generally as the crop canopy develops, wind and water erosion is minimized.
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Soil Erosion Solutions
Examine this excellent website which provides practical information to solve some of these erosion issues.
a. Grass Drainage ways
Many farmers have identified parts of a field which seem to channel surface water and which soil erosion has always been a problem. Planting a permanent grass cover on these drainage ways or allowing native wetland species to grow in the drainage way reduces soil erosion on the landscape. Some farmers might also erect some type of barrier within drainage ways to prevent water from moving too quickly off the landscape.
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b. Conservation Tillage
Crop residues minimize the amount of exposed soil. When the previous crops residue is allowed to remain on the soil surface, it can reduces the force of raindrop impact which is the principle mechanism by which soil is loosened and suspended in moving water. Maintaining as much residue cover on the soil surface will also reduce wind erosion of the soil. The greater the amount of residue that permitted to be retained, the less soil erosion occurs by either agents of water or wind. Conservation tillage practices permits some or all of the previous crop's residue to remain on the soil surface. This is especially useful for soil conservation measures on hilly landscapes where the risk of soil erosion is greatest.
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c. Tree Shelter Belts
Early European settlers realized that planting trees in rows (wind-rows) to restrict wind movement would reduce the wind speed near the tree row and thereby reduce soil erosion. Besides adding beauty and breaking up the monotony of the prairie landscape, these tree "shelter belts" also provided some protection from the persistent wind for farmer's homesteads and while they worked the land. Newer homes still employ this practice since the wind is as persistent as it has always been. Some farmers who have adopted conservation tillage practices are removing some of the shelter belts to increase land under crop production. It remains to be seen whether this is a wise decision.
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d. Conservation Reserve Program (CRP)
The Conservation Reserve Program (CRP) is a Federal Government program designed to take highly erosive lands and marginal fields out of production. The program requires farmers to plant a permanent grass cover on fields and maintain them usually for 10 years. The farmer gets annual monetary compensation for this effort. At the end of the contract, the farmer is free to renew the contract or to convert the land to agricultural production.
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Salt Accumulation (Tour Map Symbol 'Es')
General Problems
Soils formed from glacial parent materials often contain minerals with soluble salts, principally calcium (Ca) and magnesium (Mg) carbonates and sulfates and possibly some sodium (Na). During wetter periods of the year, moisture moving into the soil dissolves these salts. The enriched solutions move off the land to a lower position, or leach into the soil and move along a subsurface semi-permeable layer where the solution seeps form on hillsides. As the enriched soil-water evaporates, salts precipitate on the surface of the land. If the main salt contributor is Na, than the soil pH can be above 8.2. If the main salt contributors are Ca and Mg, the soil pH will never be below 8.2. Crops have a difficult time growing in soils with high salt accumulation, and especially with soils high in Na because it can be toxic to plant growth.
In some parts of eastern South Dakota, water is pumped from aquifers located in shale bedrock (Pierre formation). This parent material is high is soluble salts, especially Na. Applying irrigation water from these aquifers can be a major problem to agricultural production as it introduces a new source of salt to agricultural fields. In many parts of the southwestern states, production potential of thousands of acres of prime farmland has been reduced as a result of applying water of low quality. Once land degradation has begun, the problem is more difficult to rectify if the major salt constituency is Na rather than Ca or Mg.
Improper management can impact the incidence of salt-affected soils. A large or frequent application of fresh manure can introduce new salt sources to fields. In addition, the application of effluent from sewage treatment plants as an irrigation source can also increase the salt content of a field and threaten crop production potential. This is especially true for sewage effluent from municipalities whose homes use water-softener materials that are high in Na.
The incidence of salt-affected soils occurs in every county in eastern South Dakota. Thus far, it is only a localized minor problem rather than a wide-scale threat to agricultural production.
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Salt Accumulation Solutions
a. Permanent Grass Cover
If the salt-affected area of a field is localized, is not impacting agricultural production, and is only an eyesore and a nuisance, planting the area to a permanent grass cover with an adapted species might be a simple solution to the problem. A simple solution to a simple problem may control the spread of the salt-affected area to other areas of the field.
b. Drainage Improvement
If the salt-affected area is large in extent and seems to be growing in size, then improving the drainage of the land might be the best solution since the affect of salt buildup may begin to impact profitability. Installing tile drain lines will improve the drainage and remove excess water from the landscape, eventually minimizing salt buildup. Reconfiguring the landscape by installing permanent surface drainage ways is another method of moving the water from the landscape effectively and minimizing the risk of salt buildup. The investment in any of these solutions is mainly an economic decision.
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c. Adapted Crops
Certain crops or pasture grasses have the ability to tolerate moderate levels of dissolved salts or have mechanisms to exclude the uptake of excess salt constituents. Planting crops adapted to high salt conditions and/or high pH conditions is a more practical agronomic approach to solve the problem rather than attempting to change the soil chemistry or landscape configuration to an environment more conductive to crops that are not adapted to these conditions.
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d. Applying Amendments
If the major constituent of the salt affecting the soil is Na, applying and incorporating gypsum (calcium sulfate), has been shown to improve drainage and thereby the reduced the salt content in salt-affected soils. This can be rather expensive since the application rate is on the order of tons of material/acre to be effective. However, if the Na content in the soil is low, applying gypsum amendments will not improve the problem and may actually worsen it.
Applying well decomposed (well-rotted) manure on salt-affected land has also been shown to improve the drainage of the soil. The manure should be composted outside where precipitation can leach the inherent salts from the material as it decomposes. The organic constituents of the composted manure can form aggregates with the soil particles which can improve internal drainage and thereby lessen salt buildup.