|Abstract or Summary
- The objectives of this study were to evaluate the effects of site
potential, season and plant part on percent crude protein, percent
digestibility of dry matter and yield of cereal residues. Three cereal
types, club wheat (Triticum aestivum) tall, bearded wheat (T.
aestivum), and barley Hordeum vulgare) were examined.
Stress conditions more than actual site potential produced
higher crude protein levels. Stress was usually the result of low soil
moisture, though an interaction of soil moisture conditions and fertilization
were believed to also be important. When fertilizer treatments
were held constant for both high and low potential sites, crude
protein levels in all three cereals were higher on the low potential
sites. Prior to fall rains, crude protein in the leaves of club wheat
and barley on the low potential sites ranged as high as 8 and 9 percent.
Club and barley leaves on the high potential sites had only 2.2
and 3.4 percent crude protein, respectively. When only the high
potential site was fertilized, as in barley in 1978 and bearded wheat
in 1977 and 1978, crude protein levels on the high potential site were
equal to or greater than those on the low potential site.
The effect of season on crude protein levels in leaves and culms
was important only when a high initial protein content was observed.
Crude protein levels exceeding 6 percent decreased rapidly with the
onset of fall precipitation.
Crude protein levels were consistently higher in leaves as compared
to culms in all cereal types, when averaged across site potentials
and sampling dates. Crude protein levels ranged from 1.2 to
2.1 percent in culms and 3.0 to 4.1 percent in leaves.
Percent in vitro dry matter digestibility in leaves, culms and
chaff was usually not affected by site potential or plant part. However,
season consistently affected the digestibility of leaves and
culms. In most cases digestibility decreased over time, with the
greatest decrease occurring at the second sampling date. This indicated
a rapid loss of soluble carbohydrates once the rains began.
Stubble yield was, except in two instances, significantly affected
by site potential. Leaf, culm and total (leaves + culms) production was
greater on the high potential sites. Yields of standing stubble on high
potential sites averaged 700 kg/ha more than on low potential sites.
Leaf/culm ratios were consistently higher on the low potential sites.
Though not actually sampled, leaf availability was noted to decrease
dramatically over the season.