ArkValley Irrigation Grant Final Report

• Project Type: Ag/Muni Grant
• Applicant: Colorado State University Cooperative Extensions
• Project Name: Improvement of Irrigation Technology in Arkansas River Valley
• Title: Demonstrations of Irrigation Technology to Improve Crop Yields, Returns and Water Quality in the Arkansas River Valley of Colorado Summary and Conclusions
• County: Larimer
• Water Conservation - Doc Type: Final Report

The laboratory analysis conducted on the Colorado soil samples included EC" SAR,
boron, saturation percentage, soil pH, relative % water content, and a full soil cation and anion
analysis. Some pertinent summary statistics concerning these variables are given for each field in
tables 1,2, 3, and 4. Note that these tables list information about the distribution statistics, soil
chemistry, and chemical correlation matrix for each field. The means, standard deviations, and
quantile estimates for the sample salinity, SAR, boron, and SP data for each sampling depth are
displayed under distribution statistics, The mean and standard deviation of the sample pH levels
are displayed under the soil chemistry heading, along with the % cation proportions (again for
each sample depth). The chemical correlation matrix displays the joint correlation structure
between the depth-averaged In(salinity), In(SAR), In(boron), pH, SP, and relative % water
content sample data.

Figures 1 through 4 display plots of the In(salinity) data versus the In(SAR), In(boron),
and SP data for fields I through 4, respectively. Note that the data shown in figures I through 4
are the same data that the chemical correlation estimates are based on.

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Some of the pertinent sample information for each field contained in tables 1-4 and figures
1-4 is summarized below:

Field 1.

Field 2.

Field 3.

The sample salinity data displayed extremely little variation across the field. In the
0-30 cm depth, all the soil salinity samples fell between 4.5 and 6.8 dS/m. The
most variability occurred in the 60-90cm depth; the salinity values at this sampling
depth ranged from 5.6 to 10.2 dS/m (again, relatively minimal variation).
Likewise, the SAR and boron data also showed relatively little spatial variation.
The average SP levels were around 60%, and both the means and standard
deviations increased with depth. Note that the sample salinity and SAR levels
were highly correlated, and that the salinity appeared to be somewhat positively
correlated with soil texture (SP) and negatively correlated with the relative
% water content.

Both the mean and standard deviation of both the sample soil salinity and SAR
levels increased with depth in field 2. Both the salinity and SAR levels were
high enough in this field to be problematic. The boron levels were minimal, but
the SP data appeared rather variable. The salinity and SAR were again highly
correlated. However, there appeared to be no correlation between soil texture
and salinity, and only weak positive correlation between salinity and water content.

The salinity and SAR levels were much lower in field 3, as compared to
field 2. Again, however, both tended to increase with depth. As with field
2, the SP levels were quite variable, and the salinity / SAR correlation was
quite high. Unlike field 2, there appeared to be no correlation between
salinity and water content, and moderate positive correlation between salinity
and SP. There also happened to be reasonably strong negative correlation
between salinity and boron in this field (which is unusual).