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000019 Technical Advisors: Dr. Gary Banuelos Soil/Plant Scientist USDA-ARS Water Research Laboratory Fresno, California Dr. James H. Rhoades Director USDA-ARS Salinity Laboratory Riverside, California DISCUSSION Preliminarv Soil Tests Initial soil tests indbrt"d on "ytreme~' high S?l' "on'''n, on hoth of the fields being used on this project. Analysis of composite soil samples taken from the two fields used in the demonstration showed electrical conductivity (EC), a measure of salts, at the surfuce foot in Pivot #7 to average 5.2 mmhos/cm while. EC ranged from 4.7 mmhos/cm on the Apishapa silt clay to 6.9 mmhos/cm on the Bloom silt loam in Pivot #8. Sub soil samples in Pivot #7 ranged from a low of 6.1 at the 10 foot level to 8.8 mmhos/cm at the 3 foot level. EC on the Bloom silt loam was 13.6 mmhos/cm at the 2 foot level while staying in the 7.3 or less in the Apishapa silty loam, Table 2. Pivot #7 Alfalfa was planted on Pivot #7 in the late summer of 1995 but excessive rains in August and the high salt content of the s.oil and irrigation water caused a total crop failure. Looking for forage crops with more salt tolerance, grasses and sorghum-sudangrass were planted in 1996, again resulting in a crop failure as adequate stands were not achieved. In the spring of 1996, four different mixtures of grasses were planted under the first four spans ofthe pivot and sorghum-sudangrass was planted under the other four spans on August 15 and 16 with a Krause drill. The grasses and mixtures were as follows; Span # 1 - 75% Paiute Orchardgrass 25% Lincoln Smooth Bromegrass Span #2 - 100% NewHy Wheatgrass Span #3 - 33% NewHy Wheatgrass 33% Manska Pubescent Wheatgrass 34% Monarch Cicer Milkvetch Span #4 - 23% NewHy Wheatgrass 22% Paiute Orchardgrass 22% Oahe lntennediate Wheatgrass 34% Norcen Birdsfoot Trefoil 16 ~'1oY Cm<-fOoAP. .J...o f.u.J +-t..d-'VQll k rvl'< ~~ ~i