Laserfiche WebLink
<br />no\399 <br /> <br />- 5 - <br /> <br />1. In this group are such measures as contour furrowing, contour ter- <br />racing, diversions, pitting, and chiseling or subsoiling. Contour <br />terracing is frequently used in semi-arid and sub-humid climatic en- <br />vironments under high hazard site conditions and low to moderate soil <br />hazard. The measure hap been most useful and effective in breaking <br />up gully patterns on steep slopes. Field diversions are used in semi- <br />arid and sub-humid environments on sites having high to moderate soil <br />hazards and moderate to low topographic hazard. In order to maintain <br />an effective capacity on cultivated land, vegetative strips for inter- <br />ception of sediment are needed on moderate slopes above the diversions. <br />Furrowing and pitting are being tested under arid and semi-arid con- <br />ditions with soils ranging from low to high erosion and sediment yield <br />potential and topographic sites in the low to moderate topographic <br />hazard. Their success in arid climates with high and moderate hazard <br />soil conditions has not yet been established. <br /> <br />2. Crop residue use and stubble mulching are widely used under a variety <br />of soil, topographic site and climatic conditions. They are effective <br />for erosion control as a soil binder and for increased infiltration <br />capacity, particularly in semi-arid and sub-humid climatic environments <br />and under moderate and high topographic and soil hazards. Contour fur- <br />rowing, trenching, chiseling and subsoiling aid indirectly in improving <br />or increasing total infiltration into the soil. <br /> <br />3. Measures to reduce or eliminate stress on existing cover are used under <br />all site, soil and climatic conditions. Proper grazing use, rotation- <br />deferred grazing, exclusion, trespass control and other management prac- <br />tices have the effect of increasing the density of cover or reducing <br />eroding runoff by improvement of the soil infiltration capacity. Under <br />arid conditions, vegetative cover improvement by range (grazing) manage- <br />ment alone usually does not have sufficient impact on existing conditions <br />to reduce erosion significantly unless a slight or moderate change in <br />cover is critical to a site. However, livestock exclusion under arid or <br />semi-arid climatic environments and high soil erosion potential has shown <br />a substantial reduction in soil loss. Where plant density under observed <br />conditions has not noticeably increased, it is presumed that reductions <br />in soil loss are due to absence of continued compaction due to trampling. <br /> <br />4. Measures which are for preservation of existing adequate cover or cover <br />which will become adequate with time include those for fire suppression, <br />proper grazing use, and trespass control. These measures are used in a <br />variety of topographic, site, soil and climatic conditions. They are <br />most effective under semi-arid to sub-humid climatic environments and <br />high hazard soil and topographic conditions. They are usually measures <br />of low priority under arid and humid climatic environment with gentle to <br />moderate slopes and low to moderate hazard soil conditions. <br /> <br />5. Revegetation is one of the most widely applied land treatment measures. <br />It usually consists of seeding adapted grasses where natural cover has <br />deteriorated, such as where juniper and pinyon pine occupy or have <br /> <br />