Spring Barley Production Guide - College of Agricultural and Life ...

tatoes, sugarbeets, and onions are based directly on soil
test N levels and yield goal. These row crops have adequate
tissue N concentrations to allow for rapid residue
decomposition. However, mature grain residues have very
low tissue N levels which greatly slows residue decomposition
by soil microorganisms. Consequently, additional
N must be added to facilitate grain residue decomposition.
Compared to row crops, grain crops require an additional
15 lb N per acre for each ton of residue returned to
the soil, up to a maximum of 50 lb N per acre.
Legumes such as peas, beans, and alfalfa have high
tissue N concentrations and release substantial amounts
of N as they decompose. Pea and bean residues decompose
rapidly and their potential N contribution to spring
barley will be accounted for in the spring soil test N results.
By comparison, alfalfa residues typically decompose
more slowly; fall-plowed alfalfa usually provides an additional
60 to 80 lbs available N per acre beyond what is
detected by spring soil sampling.
Yield Estimates Nitrogen recommendations should be
adjusted according to the yield growers can reasonably
expect for their soil, environmental conditions, and management
practices. Historical yields usually provide a fair
approximation of yield potential if growing conditions and
cultural practices remain relatively unchanged. However,
anticipated changes in variety selection, water management,
pest management, and lodging control may require
adjustment of yield estimates. Areas of the field known
to differ significantly in yield potential may also require
adjustment in yield estimates.
Figure 5. Grain plump, grain protein, and plump kernels
in malting varieties as a function of residual plus applied
N, southern Idaho silt loam soils.
IDAHO SPRING BARLEY PRODUCTION GUIDE
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Manures Spring barley fields occasionally receive animal
manure or lagoon waste applications. Nutrient contributions
from these sources can be substantial and therefore
should be taken into account when estimating available
N. Since these materials can vary considerably in
nutrient content, they should be analyzed to develop accurate
estimates of nutrient contributions to the cropping
system. For specific information on determining nutrient
contributions from manures, refer to PNW 239, How to
Calculate Manure Application Rates in the Pacific Northwest.
Determining N Application Rates Nitrogen application
rates for spring feed barley following row crops such
as potatoes, onions, sugarbeets, beans, and peas, or following
grain with the residue removed, can be determined
from the information presented in the upper section of
Table 12. To calculate the recommended N rate, first convert
the NO3-N and NH4-N concentrations for the top two
feet of soil to lb N per acre as illustrated in Table 11. After
residual available N is determined, the fertilizer recommendation
can be determined by reading across the table
from the calculated spring soil test N level to the appropriate
yield goal. For example, the N recommendation for
a field with 80 lb of residual N per acre and a yield goal of
120 bu per acre would be 100 lb N per acre. Nitrogen
recommendations following alfalfa can be determined in
the same manner using the lower section of Table 12.
For fields previously cropped to grain with the straw
incorporated into the soil, the row crop section of Table
12 should be used with an additional 15 lb N per acre
applied for every ton of straw per acre, up to a total of 50
lb N per acre.
Malt Barley Figure 5 shows an example of the relationship
between the sum of soil plus fertilizer N applied and
malt barley yield, percent grain protein, and kernel plumpness.
Maximum grain yield under irrigation occurs at about
100 to 140 lb N per acre depending on variety and yield
potential. At N rates higher than that required for maximum
yield, grain protein can increase to unacceptably
high levels while percent plump kernels can drop below
desirable levels. This response varies considerably among
varieties and, therefore, varietal response should not be
predicted from this graph. However, as the result of these
N effects on malt barley quality, malt barley N recommendations
are somewhat lower than those for feed barley.
Total N recommendations for malt barley will typically be
20 to 40 lb N per acre lower than those presented in Table
12 for feed barley.