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<br /> <br />USE OF AGRICULTURAL <br />CHEMICALS <br /> <br />Applications of pesticides and fertilizers <br />to cropland can result in significant additions of <br />contaminants to water resources. Some pesticides <br />are only slightly soluble in water and may attach <br />(sorb) to soil particles instead of remaining in solu- <br />tion; these compounds are less likely to cause <br />confamination of ground water. Other pesticides, <br />however, are detected in low, but significant, <br />concentrations in both ground water and surface <br />water. Ammonium, a major component of fertil- <br />izer and manure, is very soluble in water, and <br />increased concentrations of nitrate that result from <br />nitrification of ammonium commonly are present <br />in both ground water and surface water associafed <br />with agricultural lands (see Box 0). In addition to <br />these non point sources of water contamination, <br />point sources of confamination are common in <br />agricultural areas where livestock are concen- <br />trated in small areas, such as feedlots. Whether the <br />initial contamination is present in ground water or <br />surface water is somewhaf immaterial because the <br />close interaction of the two sometimes results in <br />both being contaminated (see Box Pl. <br /> <br /> <br />Applying chemicals to cropland in Maryland. <br />(Photograph by David Usher.) <br /> <br />"Whether the initial contamination is <br />present in ground water or sU1jace water is <br />somewhat immaterial because the close <br />interaction of the two sometimes results <br />in both being contaminated" <br /> <br />61 <br />