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<br />~ <br />. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />. <br /> <br />.. <br /> <br />Technical Advisors: <br /> <br />Dr. Gary Banuelos <br />SoiVPlant Scientist <br />USDA-ARS Water Research Laboratory <br />Fresno, California <br /> <br />Dr. James H. Rhoades <br />Director <br />USDA-ARS Salinity Laboratory <br />Riverside, California <br /> <br />DISCUSSION <br /> <br />Preliminary Soil Tests <br /> <br />Initial soil tests indicated an extremely high salt content on both of the fields being used on this project. <br />Analysis of composite soil samples taken from the two fields used in the demonstration showed electrical <br />conductivity (EC), a measure of salts, at the surface foot in Pivot #7 to average 5.2 mmhos/cm while. <br />EC ranged from 4.7 mmhos/cm on the Apishapa silt clay to 6.9 mmhos/cm on the Bloom silt loam in <br />Pivot #8. Sub soil samples in Pivot #7 ranged from a low of6.1 at the 10 foot level to 8.8 mmhos/cm at <br />the 3 foot level. EC on the Bloom silt loam was 13.6 mmhos/cm at the 2 foot level while staying in the <br />7.3 or less in the Apishapa silty loam, Table 2. <br /> <br />Pivot #7 <br /> <br />Alfalfa was planted on Pivot #7 in the late summer of 1995 but excessive rains in August and the high <br />salt content of the soil and irrigation water caused a total crop failure. <br /> <br />Looking for forage crops with more salt tolerance, grasses and sorghum-sudangrass were planted in <br />1996, again resulting in a crop failure as adequate stands were not achieved. In the spring of 1996, four <br />different mixtures of grasses were planted under the first four spans of the pivot and sorghum-sudangrass <br />was planted under the other four spans on August 15 and 16 with a Krause drill. <br /> <br />The grasses and mixtures were as follows: <br />Span # I - 75% Paiute Orchardgrass <br />25% Lincoln Smooth Bromegrass <br /> <br />Span #2 - <br /> <br />100% NewHy Wheatgrass <br /> <br />Span #3 - <br /> <br />33% NewHy Wheatgrass <br />33% Manska Pubescent Wheatgrass <br />34% Monarch Cicer Milkvetch <br /> <br />Span #4 - <br /> <br />23% NewHy Wheatgrass <br />22% Paiute Orchardgrass <br />22% Oahe Intermediate Wheatgrass <br />34% Noreen Birdsfoot Trefoil <br /> <br />15 <br />