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

Elemental Concentrations
Tall fescue accumulated the greatest amount ofCI- and Na+. Broad-Ieafbirdsfoot accumulated
the greatest amount of Ca2+ and Mg2+ among the three species. Generally tissue Ca2+
concentrations were higher in treatments 1 thru 3 (good soil) than treatments 4 thru 6 (poor soil)
for all species, while Na+ and CI- concentrations increased in shoot tissue in treatments 4 thru 6
(Table 5 and 6). Generally, soil EC levels and all tested elements increased with addition of poor
quality water. Interesting to note; soil EC did not increase to the same magnitude in postharvest
soils from tall fescue as compared to both varieties of birds foot trefoil (see Table I).

Discussion

Based upon the conditions described and presented by Colorado State University Extension, tall
fescue appeared to tolerate the poor soil and poor quality water conditions better than narrow and
broad-leafbirdsfoot trefoiL

Plant tolerance to salinity is usually appraised in one of three ways: I) the ability ofa plant to
survive on saline soils, 2) the absolute plant growth or yield, and 3) the relative growth or yield on
saline soil or with saline water compared with that on nonsaline conditions. In this study, the
third point of criteria was primarily used for determining salt tolerance. Salinity can affect plants
at all stages of development, but sensitivity sometimes varies from one grov,'!h stage to the next.
Tall fescue did not appear to show significant decreases in dry matter production among the
different treatments at any clipping, although DM gradually increased to a point in its growth
cycle and then gradually decreased. For both narrow- and broad-Ieafbirdsfoot; significant DM
differences among the treatments were easier to detect. Interestingly, treatments containing either
poor soil or poor quality water slightly stimulated DM production in both varieties of birds foot,
especially in narrow-leaf The influence of clipping frequency or interval regime on biomass
production was not evaluated in this study, but likely influences growth of tall fescue and
birdsfoot trefoiL

Current evidence indicates that, in general, plant growth of any plant is most closely related to
water uptake. We found this relationship to be true in our study. During our designated growing
season, tall fescue received up to 27 liters of water per pot, while both varieties of birds foot
trefoil received approximately 20 liters, irrespective of treatments. Consequently, total dry matter
yields were considerably greater for tall fescue. Care was taken with irrigation to avoid contact
with plant and water applications. This precaution allowed for a more accurate evaluation to be
made on the species ability to accumulate ions through their roots, since plants can absorb ions
directly through their leaves.

Changes and differences in shoot ion concentrations with salinity treatments could be observed in
the three species, Generally leaves are susceptible to injury by the toxic accumulation of CI", or
Na-, or both in the leaves. Injury may depend more on leaf characteristics and the leaves' rate of
absorption than on a plant's tolerance to soil salinity. Rates of salt absorptions may increase when

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