One problem is that as nitrogen is leached from the soils, it collects in the ground water and in surface streams. This can cause eutrophication, an excess growth of plants and algae, in nearby streams and lakes (Weil, et al, 441). Also, concentrations of nitrate of 10 mg/L or more in drinking water can cause methemoglobinemia, or blue baby syndrome in infants (Hubbard, 802). In well-drained soils, organic material, which, of course, contains nitrogen, "may decompose faster than it is replenished (Dolman and Bud, 1967)" (Gambrell, et al, 321). So, in order to s... ... middle of paper ... ....; "Nitrate transport on a sandy coastal plain soil underlain by plinthite."
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Raw water undergoes physical screening to remove coarse material and debris as it comes to the water treatment plant. Screening separates particles according to their size alone. As mentioned by Hendricks (2006), the objective of the screen is to accept a feed containing a mixture of particles of various sizes and separate it into two fractions, an underflow that is passed through the screen and an overflow that is rejected by the screen. (p. 121) Screening is further divided into coarse and fine screens. Raw water undergoes coarse screen to eliminate floating material of fairly large size as preliminary treatment for the next step.
(2) Snyder, B.M., R.M. Dennis, M.J.S. Roth, R. Krishnan, and H.W. Parker, "Evaluation of soilwashing process for 'unwashable' clays and silts from the Palmerton zinc site," Remediation, pp. 69-80, Winter 1995/96, (1995).
The Leaching Requirement During Irrigation The leaching of soluble salts from the plant rooting zone is a pivotal concern when irrigating cropland. Irrigation water is used to maintain crop productivity, so drought conditions need not occur to induce irrigation measures. Irrigation simply provides supplemental precipitation that may not be achieved through natural processes, i.e. rainfall. Basically, leaching is described as passing additional water through a medium to remove unwanted materials.
The process of eutrophication happens when natural as well as artificial nutrients, mostly nitrates and phosphates, find their way into an aquatic or terrestrial ecosystem. When these nutrients are added to a water body or soil the consequences can show up in numerous forms. One that flourishes when there is extra nutrients is the growth of the microscopic organisms known as phytoplankton (blue-green algae) in freshwater rivers and lakes. When there is an overabundance of them in a lake or river they show up as a green color on top of the water. Excessive algae bloom and weeds are two other results that can also appear when too many nutrients enter a water body.
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Westermann, J.L. Wright, R.E. Peckenpaugh, 1995, Nitrate Leaching Under Furrow Irrigation as Affected by Crop Sequence and Tillage: Soil Science Society of America Journal, 59: 204-210. Poincelot, Raymond C., 1986, Toward a More Sustainable Agriculture: Westport CT, AVI Publishing Co. Inc., 241 p.