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<br /> <br />W <br />N <br />1\) <br />tv <br /> <br />~~lt ~22BIDY12t!~n in the ~Q!l <br /> <br />The introduction of irrigation into the fie1d of <br /> <br />agriculture on a large scale has had the effect of diverting <br /> <br />salt to the soi1. This is sa1t that, in previous years, had <br />been dedicated by nature to the oceans. Through irrigation. <br />salt is being intercepted enroute to its time-honored <br /> <br />destination. placed upon and through the soil mantle, <br /> <br />concentrated by evapotranspiration and leaching, and <br /> <br />returned to the stream. This series of events may take <br /> <br />place many times in a single river basin or stream prior to <br /> <br />discharge. Each use results in increased concentration and <br />the cumulative effect is the magnification of a normal salt <br /> <br />content several times that expected under non-irrigating <br /> <br />waterway conditions (5). <br /> <br />Accumulations of salt in irrigated soil must be avoided. <br /> <br />inasmuch as the land wou1d soon become too saline to support <br />plant life. If normal rainfall cannot flush the sa1t from <br /> <br />the root zone. excess water must be applied during regular <br />seasonal irrigations to prevent buildup. The excess <br /> <br />represents the "leaching requirement" necessary to prevent <br /> <br />salt accum~lation above a prescribed 1evel. Fai1ure to <br />maintain the level can become a 1imiting factor to further <br /> <br />agricultural development in a given area. The increased <br /> <br />application of water to achieve a proper leaching <br /> <br />21 <br /> <br />