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<br /> <br />United States <br />Department of <br />Agriculture <br /> <br />Agricultural Pacific West Area <br />Research <br />Service <br /> <br />u.S. Salinity Laboratory <br />450 W. Big Springs Road <br />Riverside, CA 92507-4617 <br /> <br />Tel. 909-369-4867 . <br />Fax. 909-342-4962 <br />Email. Jrhoades@ussl.ars.usda.gov <br /> <br />November 8, 1996 <br /> <br />Jim Valliant <br />Regional Irrigation Specialist <br />Colorado State University <br />411 North 10th Street <br />Rocky Ford, CO 81067 <br /> <br />Dear Jim: <br /> <br />Please find enclosed a summary of the mobile-assessment and laboratory analysis results- <br />for the fields involved in what Scott called the "Colorado Expedition" trip. Also enclosed is a <br />table of analytical data for the soil samples we collected. We normally would not do so much <br />laboratory work, but we did this time to make sure you got some good data/results-since the <br />fields were drier than we like them to be for our instrumental measurements. <br /> <br />A few comments about the analytical results: Sulphate is the dominant anion; the cations <br />are mixed and generally in the order: Na>Mg>Ca. Boron is low and not a problem; nor is pH. <br /> <br />Now a few comments about the results given in the "Expedition Report". Average soil <br />salinity levels(about 5.7-8.0)are high enough in field #1 to reduce the yield of crops like beans, <br />alfalfa, clover, fescue, mil kvetch, maize(forage), sudangrass(forage), trefoil and other such <br />sensitive and moderately sensitive crops and forages-especially those grown for vegatative- <br />growth. However, the observed levels should not cause undue yield-losses for more salt-tolerant <br />crops like wheat, sugarbeets, barley, maize(grain), taIl wheatgrass, sorghum(grain), etc. The <br />above conclusion assumes irrigation by flood techniques is used (as was the case for this field) <br />with reasonably good irrigation management during the seedling establishment period to obtain <br />satisfactory stand using whatever water has been being used there. This conclusion is based on the <br />observation of the levels of soil salinity that have resulted from the use of that water and on the <br />salt-tolerance data of the USSL. It precludes the use of sprinkler-irrigation-since this could <br />introduce foliar-salt/uptake problems, as discussed next in terms of the other fields. The levels of <br />salinity within field #1 are rather uniform as fields go, as you can see in Tables I & 5 and in <br />Figures 6 & 10. The levels of SAR in the soil are not overly high; I would not expect a serious <br />~pdicity-related problem in this field, especially given the corresponding salinity levels and fact <br />that the field is furrow-irrigated. <br /> <br />Soil salinity levels in field #2 are sufficiently high to limit crop production to only salt- <br />tolerant crops such as barley, sugarbeets, rye, bermudagrass, etc. (The mean ECe is essentially 10 <br />