III. SOILS, AGRICULTURE, AND ENVIRONMENT
Natural Vegetation and Conservation Buffers Next Section>>
Several farming practices that protect soil and water resources by maintaining permanent vegetative cover are described in this section. They include preserving the natural vegetation, usually forest, and establishing conservation buffers. Some of the farm practices described below are commonly used in Indiana, but are not considered in the contest.
Subsections:Natural Vegetation | Conservation buffers
Forest was the original vegetation of most of Indiana. Well managed forest vegetation is very effective cover for preventing soil erosion (Fig. 21). The impact of raindrops is reduced when they strike the leaves or stems of the canopy. Some of the rain falls to the soil from the canopy, some runs down the trunks of trees, and some is left to evaporate from the trees. The raindrops falling from the tree canopy pick up some energy as they fall, but this energy is largely absorbed by a mat of fresh or decaying leaves on the soil surface. Very little rainfall strikes the mineral soil directly. Furthermore, soil in the forest absorbs water very quickly, so most of the rain soaks in rather than runs off. Any soil in Indiana can be left in, or planted to, forest. Well managed forests are protected from grazing.
Prairie vegetation covered part of the state when the settlers first arrived. It is also very effective in controlling soil erosion because it forms a dense sod cover. Very little natural prairie remains in Indiana, but there is renewed interest in preserving and establishing prairie areas and in using native prairie grasses for pasture and roadside planting.
Native vegetation has protected the soil on which it grows for thousands of years, and will continue to protect it in the future. Therefore keeping a soil in native vegetation, or restoring it, is a suitable land use for any soil.
| Always mark Natural vegetation YES. |
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Conservation Buffers
Conservation buffers are areas or strips of land in permanent vegetation, designed to intercept pollutants. They slow water runoff, trap sediment, and enhance water infiltration into the soil in the buffer. They also trap fertilizers, pesticides, bacteria, pathogens, and heavy metals, minimizing the chances of these potential pollutants reaching surface and groundwater sources. Buffers also trap snow and reduce soil erosion by wind. Some buffers protect livestock from harsh weather. Wooded buffers can also provide a source of future income. They can enhance wildlife habitat, improve water quality, and enrich aesthetics on farmlands. They help farmers protect soil and water quality, improve fish and wildlife habitat, and demonstrate a commitment to land stewardship. Properly installed and well maintained buffers help diversify the “look” of a farm, adding to its beauty, recreational opportunities, and land value.
Conservation buffers can be used along streams and around lakes or wetlands, or installed at field edges and within fields. Buffers are most effective when they are used in combination with other conservation measures as part of a planned conservation system. Eight kinds of buffer strips are described below. The first three are considered for soil evaluation.
Grassed waterways: Strips of grass in areas of cropland where water concentrates or flows off a field. While they are primarily used to prevent gully erosion, waterways can be combined with filter strips to help trap contaminants and sediment. Shallow surface drainage systems should have grassed waterways in the lower parts of their drainage channels. Grassed waterways are used in sloping cropped fields. For soil evaluation they are marked according to the rule below, even if the soil pit is not in a cropped field.
| Mark Grassed waterways YES for soils with slopes of 3% to 18%. |
Windbreaks: A row of trees, shrubs, or other vegetation used to reduce wind erosion, protect young crops, and control blowing snow. Windbreaks are placed near the field boundary that is most nearly perpendicular to the prevailing wind direction. Since the wind is mainly from the west in Indiana, most windbreaks are oriented north-south. The parent materials of many sandy and moderately sandy soils were deposited by wind, and these soil are especially subject to wind erosion. Many of these soils are common in Soil Region 1, but windbreaks are also used in other regions.
| Mark Windbreaks YES for soils with sandy or moderately sandy surface texture. |
Filter strips: Strips of grass or other vegetation used to intercept or trap sediment, organics (such as manure), pesticides, and other pollutants before they reach a water body (Fig. 23). Some pesticides are broken down to harmless materials by microbial action in the filter strip. In Indiana, filter strips protect the soil from erosion. The strips typically vary in width from 20 feet on nearly level soils to 60 feet on sloping soils. They can be planted to forage crops, and hay can be harvested. Crop removal might be essential to the effectiveness of the strip because plant nutrients that erode from a field are trapped in a filter strip, and the fertility level of the strip could become excessively high if no nutrients were removed. Trees can also be harvested from filter strips.
Fig 23. A filter strip and a surface inlet.
To be effective, filter strips must be placed along drainageways and streams that lead to a larger water body. Drainageways are low in the landscape and often in poorly drained soils, and streams are often surrounded by terrace or floodplain landforms, so these criteria are used in soil evaluation rules. In practice, however, filter strips may be used on many other soils. Soils on slopes more than 18% are not used as cropland and thus do not need filter strips.
| Mark Filter strips YES for soils with both characteristics: 1. Outwash landform or floodplain landform or poorly drained, and 2. slope of 18% or less. |
Field borders: Strips of perennial vegetation planted at the edge of a field. They can be used for a turn area or travel lanes for farm machinery.
Contour grass strips: Narrow bands of perennial vegetation established across the slope of a crop field, between strips of crops. They can reduce sheet erosion and reduce movement of sediment, nutrients, and pesticides.
Salt tolerant vegetation: Vegetation that is tolerant to high contents of salts in soils. It is used in southern Indiana where soils have been contaminated by spills of brine near oil wells.
Riparian buffers: Streamside vegetation consisting of trees, shrubs, and grasses that can intercept pollutants from both surface and ground waters before they reach a stream. They also help restore eroded stream banks.
Alley cropping: An agroforestry practice consisting of
growing trees or shrubs in rows or corridors with alleys of agronomic crops
or forage between them. Both the forestry and agronomic crops are harvested.
