introduction higher market prices relative to the predominant soft white class has increased grower...
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IntroductionHigher market prices relative to the predominant soft white class has
increased grower interest in the production of hard red spring wheat.
Less hard red wheat is currently grown under irrigation in part due to
concerns about productivity and the management required for producing
wheat with acceptable protein. Discounts for low protein need to be
avoided or minimized to maximize the returns for the hard red class.
Increasing late season available N is frequently used to improve grain
protein of irrigated hard red spring. But the N is frequently applied
without knowing the likelihood of significant protein enhancement. Flag
leaf total N concentration (FLN) was reported to provide a reasonable
indication of the extent to which late season N can increase grain protein
(1,2 ). Little if any protein increase with late season N was reported in
these studies if FLN concentrations at heading measured 4.2-4.3%.
Whereas most reports of flag leaf N involve sampling at heading (FHD) or
flowering (FFL), earlier sampling at full flag leaf emergence (FEM) would
provide additional time for (1) the wheat’s N status to be determined, (2)
the decision made to provide supplemental N for protein enhancement,
(3) the application to be scheduled and applied, and (4) in some cases
the time necessary to fully incorporate the applied N either by irrigation
or natural rainfall.
In a practical sense, although sampling at heading is typically the target
sampling stage, it may not be feasible to sample large numbers of fields
precisely at the same growth stage. Knowing the FLN change between
Feekes stages 9 (ligule just visible), 10.5 (mid heading), and 11.5 (mid
flowering) may be useful in interpreting FLN of samples collected either
before or after heading. Information is needed on the flag leaf N
response of hard spring wheat to growth stage, and other practices
potentially affecting production and grain protein.
Therefore the objectives of this study were to (1) examine the effects of
planting dates and varieties on flag leaf N contents from full emergence
to flowering in a replicated study, and (2) to monitor FLN changes in
grower wheat fields in relation to reported critical FLN values.
MethodsResponse to Variety and Planting Dates
A three year field study was conducted on a Greenleaf silt loam (fine-
silty, mixed, superactive, mesic, xeric calciargids) at the University of
Idaho Parma Research and Extension Center to measure the flag leaf N
response of three hard spring varieties (Vandal and WPB 936 hard reds,
and ID377S hard white) grown under wide ranging planting dates (late
fall, early spring, and late spring), with four late season N rates (0, 28, 56,
and 84 kg ha-1) applied at heading. Factorial treatments were arranged
in a randomized complete block with four replications.
Planting dates ranged from 11-23 Nov for the late fall planting, 7-15
March for the early spring planting, and 10-14 April for the late spring
planting. Urea N was topdressed each year to the entire experiment
when the early spring planting was emerging (dates ranged from 23-30
March). Timing corresponded to the tillering stage for the late fall
planting and preceded the late spring planting by 15 to 19 days. This N
was dependent on rainfall for incorporation and significant rain in any
year exceeding 5mm did not occur prior to the first irrigation on 23 April
(1999), 24 April (2000), or 19 April (2001). The trial was irrigated each
year with sprinklers.
Flag leaves were collected only from treatments that did not receive late
season N. The samples in the 2000 and 2001 seasons for each variety
and planting date were collected at full flag leaf emergence (Feekes 9),
mid-heading (Feekes10.5), and mid-flowering (Feekes11.5). Tissues were
dried and ground and total N was determined by combustion analysis at
the University of Idaho Analytical Services Laboratory. Treatment
effects were evaluated with ANOVA and Regression options in SAS 8.0.
FROM FLAG LEAF EMERGENCE TO FLOWERING: INTERPRETING N CONTENTS FOR IRRIGATED WHEAT PROTEIN . B. Simko, B. Brown, S. Reddy, and J. Neufeld, Oregon State University and University of Idaho
Methods-continuedFlag Leaf Monitoring of Producer Fields
Flag leaves were collected at FEM, FHD, and FFL from 14 producer fields
of irrigated hard red spring wheat in southwest Idaho and eastern
Oregon over three seasons. Flag leaves were frozen or refrigerated until
they could be oven dried, ground and submitted for total N (Kjeldahl)
analysis at local commercial laboratories. Information from producers
was obtained regarding the N fertilization practices used during the
season.
Head samples were collected from each field at late dough, the heads
dried sufficient to thresh the grain, and the protein determined (12%
moisture) by Kjeldahl. Grain protein of the harvested wheat was also
obtained when available from the producer based on samples they
submitted from storage to local elevators or distant FGIS facilities.
However, harvest samples were not collected using the same sampling
pattern as the flag leaves or late dough samples and in some cases were
averages of several fields. Therefore, FLN was related to late dough
protein because the sampling was more consistent. Late dough and
harvest protein were linearly related (r2=0.78).
ResultsPlanting Date and Variety Effects on Flag Leaf N
Planting dates significantly affected FLN, especially in 2000 (Fig. 1 ). FLN
was highest for the late fall planting at each growth stage in the 2000
season and FLN for the late spring planting was lowest in two of three
samplings. In contrast, FLN in 2001 did not differ as widely among
planting dates as in 2000. FLN for the late fall planting in 2001 was lowest
at FEM whereas the late spring planting was highest at FFL.
Varieties differed significantly in FLN in 2000 with Vandal and WPB 936
averaging higher than ID377S at all growth stages . In contrast, WPB 936
FLN was higher than both Vandal and ID377S FLN in 2001.
FLN averaged across all variety and planting date treatments in 2000
decreased 0.56%N from the first to last sampling. In contrast, FLN in
2001 decreased only 0.07%N from the first to last sampling.
Flag Leaf N Monitoring in Producer Fields
Producer fields sampled over the 1999-01 period are listed in Table 1 with
their designations, late dough protein and N fertilization. Yields ranged
from 6.05 to 8.54 Mg ha-1 (90-127 bu A-1) and protein from 12.6 to 17.4%.
Only 5 of the 14 producer fields had late dough protein exceeding
14%despite late season N intervention (applied between boot and
flowering stages) in all but two fields. Late season N (20-135 kg ha-1) was
applied by various means; solutions through the lines, topdressed dry,
foliar, and water run in furrows. Repeated applications were made in
some fields.
FLN values from the 2000 season are suspect as they fluctuated widely
among growth stages. We find it unlikely that these fluctuations occur
naturally within such short time periods. We suspect analytical
difficulties in the commercial lab used and the FLN results from 2000 are
not included in the following discussion.
FLN at FEM ranged from 3.12 to 4.98%N in 1999 and 2001 grower fields.
FLN in producer fields either increased, was unchanged, or decreased
after FEM and the change was not related to the total late season N
applied. Late N was, in some cases, applied in repeated applications
throughout the period of sampling. The change in FLN from FEM to FHD
ranged from a decrease of 0.52% N to an increase of 0.84% N over a
period of time ranging from 3 to 10 days. The FLN change was unrelated
to the number of days between samplings. FLN, with minimal mid or late
season N applied (22-34 kg ha-1), decreased in producer fields at a daily
rate ranging from 0.036 to 0.086% N.
Results -- continuedFLN generally decreased in producer fields after heading with the
exception of two fields where FLN slightly increased as a result of late
season N > 112 kg N ha-1. The largest drop in FLN occurred in 1999
(decreases of 1.55 and 1.68% N) with minimal late season N applied.
Of all samplings, FLN at FFL would be expected to be the most closely
related to late dough protein, but there was no significant relation
between them when the data from all years were included (data not
shown ).
Previously reported critical levels of 4.2-4.3% FLN at heading could not
be supported from these limited data from commercial fields. Several
fields had FLN at heading or later that exceeded the critical levels and
yet late dough protein was 13% or less. FLN was a poor indicator of
grain protein in producer fields when used on a commercial scale.
References1. Tindall, Terry A., Jeffrey C. Stark, and Randall H. Brooks. 1995. Irrigated spring wheat response to topdressed nitrogen as predicted by flag leaf nitrogen concentration. J. Prod. Agric. 8:46-52.
2. Westcott, Mal, Joyce Eckhoff, Rick Engel, Jeff Jacobsen, Grant Jackson, and Bob Stougaard. 1997. Rapid diagnosis of grain protein response to late-season nitrogen in irrigated spring wheat. Proceedings, Western Nutrient Management Conference. Salt Lake City, Utah. March 6-7. pp 77-81.
Figure 1. Flag leaf N contents at full flag leaf emergence (Fem), heading (Fhd), and flowering (FFl) growth stages as affected by planting dates. Parma, 2000-2001.
Fla
g L
eaf
N (
%)
3.0
3.5
4.0
4.5
5.0
5.5Parma, 2000 Late Fall
Early SpringLate Spring
Fla
g L
eaf
N (
%)
3.0
3.5
4.0
4.5
5.0
Parma, 2001
ab a
ac
bc
c
b
aab a a
b baab
a
flem hdng flrg
Sampling Growth Stage
Fla
g L
ea
f N
(%
)
3.0
3.5
4.0
4.5
5.0
5.5Parma, 2000
Fla
g L
ea
f N
(%
)
3.0
3.5
4.0
4.5
5.0
Parma, 2001
flem hdng flrg
Sampling Growth Stage
ab
a
a
a
b
a
ab
ab b
a
bb
a
b
b
VandalWPB 936ID377S
Figure 2. Flag leaf N contents at full flag leaf emergence (Fem), heading (Fhd), and flowering (FFl) growth stages as affected by varieties. Parma, 2000-2001.
Figure 3. Flag leaf N in 14 grower fields as affected by wheat growth stage. The number following the field designation in the key is the late season N applied.
Fla
g L
eaf
N (
%)
2
3
4
5
6Malheur Co, 1999
Cow Valley 81
Fruitland 34Nyssa 22
Fla
g L
eaf
N (
%)
2
3
4
5
Malheur Co, 2000
Clark 45Locust 22
Fla
g L
eaf
N (
%)
2
3
4
5
Malheur Co, 2001
Crn B4 45Crn B1 45Crn Lc 45Crn S2 45
Growth stage
Fla
g L
eaf
N (
%)
2
3
4
5
Washington and Ada Co, 2001
Heading FloweringFlag Leaf just emerged
Vandal 0 King 0
Noble 0YamSh 134YamBCt 134
Table 1. Treasure Valley HRS Late Dough Protein and WheatNitrogen Fertilization. 1999-2001
Nitrogen AppliedField County Dough
ProteinPreplant Mid
seasonLate Total
% ---------------kg ha-1--------------
1999Frtlnd Malheur 14.06 103 22 34 159Nyssa Malheur 13.88 134 0 22 157CowV Malheur 17.35 168 0 81 249
2000CrnClk Malheur 14.35 157 0 45 202CrnLcst Malheur 13.09 157 0 22 179
2001CrnB4 Malheur 12.60 168 0 45 213CrnB1 Malheur 13.19 179 0 45 224Crnlc Malheur 12.91 168 0 45 213CrnS2 Malheur 12.90 168 0 45 213Noble Ada 13.14Yamsh Ada 13.76 84 56 134 275Yambct Ada 15.88 112 0 134 252RbtsVa Washington 13.89 0 123 0 123RbtsKg Washington 14.89 0 123 0 123
SummaryPlanting dates and varieties significantly affected FLN at specific growth stages. FLN monitoring across seasons in producer fields receiving late season N indicated that FLN was not consistently related to late dough protein. We found annual variability in the FLN-protein relation as well as the FLN change between growth stages. The influence of seasons, cultural practices, and other factors will make interpretation of FLN and it’s consistent use every year for predicting the need for protein enhancing late season N intervention difficult.