may not sufficiently reduce sediment yield and dust emissions from erosional sites , will not protect against gully erosion where runoff is allowed to concentrate, and may not protect young seedling from windblown sediment Meeting the soil-loss tolerance standard is only one part of a com prehensive conservation plan.
Research date , scientific knowledge ,and professional judgment are involved in setting soil-loss tolerance values. Those judgments in the 1950s were within the context of social and economic conditions and the agricultural technology available at the time. Soil-loss tolerance values have become so institutionalized that suggestions of value change often are resisted (Es-seks et.,2000;Hall et al.,1985;McCormack and Young,1981)
Relation of T Values to soil Formation
Two soil-formation rates are considered in setting T values. The first is the rate of topsoil formations.A high-quality,well-aggregated surface soil layer greater than 10 in (250 mm) that allows root growth,good aeration, and soil-moisture conditions, and contains an adequate supply of plant nutrients and organic matter , is required for