When the contaminants are on the land (already available), physical detachment generally results from the impact of raindrops or from shear forces in overland sheet flow or concentrated flow. Unprotected soil and surface-applied wastes, fertilizers, and pesticides may be detached in this way. Therefore, the primary control measures to prevent detachment are those that reduce the impact of raindrops, such as vegetative cover or mulch, and those that control the velocity of water moving across the landscape, such as minimum or no tillage.
An understanding of the particular contaminants and how they react on the land or in the environment is helpful in establishing proper methods of control. Preventing detachment can involve control of particular constituents within animal waste (see section 651.0302(a)). If phosphorus is an identified water quality problem, then practices must be applied to prevent detachment of phosphorus. If the problem is low dissolved oxygen in a stream or lake (possibly from excessive organic matter) or a fish kill from high concentrations of un-ionized ammonia, then controls for these constituents should be applied.
Weakly bonded substances, nitrates, and bacteria can be detached and transported by water moving through the soil. Management practices to control detachment include:
• Applying less soluble fertilizers
• Applying wastes in split applications to prevent too much N from being converted to nitrate at one time
• Applying less irrigation water to fields when high levels of soluble substances are available
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