Baking Quality Response to Late Season N with Variable Moisture During Grain Fill' K' OBrien, B' Bro

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Baking Quality Response to Late Season N with
Variable Moisture During Grain Fill. K.
OBrien, B. Brown, and R. Gibson. University of
Idaho
Results continued Flour Protein-Fpro generally
declined as additional water during grain fill
increased yield. The higher EN rate increased
Fpro in two years but LSN increased Fpro in all
years. The increase in Fpro with 90 kg ha-1
ranged from 0.6 to 2.1 percentage units. The
Fpro response to LSN was generally greatest with
the first LSN increment. Mixograph Peak-Mpk
decreased with additional water during grain fill
and these effects were generally greater than the
effects of EN and LSN. EN increased Mpk slightly
whereas LSN had little affect other than in 1997
when it reduced Mpk. Mixograph Tolerance-Higher
Mto gives more flexibility for adjusting mixing
time to capture optimum gluten strength.
Watering during grain fill had mixed effects,
appreciably decreasing Mto in 95 and 97 but
increasing Mto in 96. LSN generally reduced
Mto. Seasons typically had more influence on Mto
than LSN treatments. Mixograph Height-Mht, an
indication of gluten strength, decreased with
additional water during grain fill. Moisture and
seasonal influence generally were greater than
LSN affects, which were mixed, appreciably
increasing Mht in 1997 but reducing it slightly
in 1998. Mixograph Absorbance-Mab is the capacity
of flour to absorb moisture. Added moisture had
minimal effects on Mab other than in 96 when IR
reduced Mab 5.8 units. LSN typically increased
Mab from 0.4 to 2.6 units, but the effects were
minimal compared to the seasonal influence. Bake
volume-Added moisture during grain fill had
contrasting effects in different years,
increasing Bvo in 95 but reducing it in 96 and
98. LSN increased Bvo every year, moreso in
97-98 than in 95-96. Bvo tended to increase
with higher protein regardless of whether the
protein increase was due to additional N or lower
yields from moisture stress. Bvo improvement
with LSN was limited if wheat without LSN was at
or above 15 protein. Baking volumes were
not consistently related to specific protein
concentrations. For example, 96 Bvo associated
with 17 protein was smaller than Bvo in 97 or
98 wheat testing less than 14 protein. Baking
quality is clearly dependent on more than crude
protein. Nevertheless, baking quality was
invariably improved when protein was enhanced
with LSN. Bvo/Fpro-Higher R values indicate
better quality protein. Despite increased
protein with stress, R decreased. In contrast,
with the exception of 97, protein quality was
only marginally affected by LSN. Acceptable
protein and baking quality was achieved in this
study without sacrificing yield by stressing
wheat during grain fill. Whereas yield limiting
late moisture stress increased protein in three
years, overall end quality (represented by Bvo)
was improved in only two years, and protein
quality (represented by R) actually decreased
each year. In contrast, LSN improved both Fpro
and Bvo every year of the study without affecting
protein quality (R).
Introduction High protein premiums and
higher prices have increased traditional
irrigated soft white wheat grower interest in the
production of the hard red classes. Higher
returns from the hard red spring class are
dependent on avoiding discounted prices for low
protein (lt14). The importance of adequate
nitrogen (N) for yield and protein is generally
appreciated. Late season N (LSN) fertilizer
applied at heading (Feekes 10.1-5) has increased
wheat protein in several environments and the
practice is common in many hard wheat production
areas. But LSN rates appropriate for protein
enhancement in limited rainfall low yield
environments may not be appropriate for irrigated
high yield environments. Producers of high
yielding irrigated hard red wheat frequently fail
to consistently raise wheat protein to desirable
levels (14) with low to moderate LSN rates
reported in published studies (1,2). Higher
wheat protein is generally associated with
improved baking quality, thus the high protein
premium and low protein discounts in market
prices. But there are reports that LSN may not
improve wheat baking quality even if wheat
protein is increased (3). Yield is
frequently limited by moisture during grain fill.
Many irrigated producers and those that serve
them commonly believe that higher and acceptable
protein is only possible with late season
moisture stress. The effect of moisture stress
on the protein and baking quality response to LSN
has received little attention. Objective
To determine the milling and baking quality
response to LSN in wheat that varies in yield due
to late season available moisture. Methods
A hard red spring wheat field study was conducted
for four seasons (1995-98) at the University of
Idaho Parma Research and Extension Center
involving early season N (ESN) rates of 67 and
135 kg ha-1, LSN rates of 0, 45 and 90 kg ha-1
applied at heading, and irrigation treatments
(IR) of 0, 0.5, and 1.0 times estimated ET from
the last uniform wetting prior to flowering. ESN
and LSN were topdressed urea incorporated with
sprinkler irrigation. Treatments were arranged
as a split plot randomized complete block design
with four replications. The ESN rate and IR
treatments were randomized among the main plots.
Main plots were 3m wide and 27.4m long and were
divided into three subplots of LSN each 9.1m
long. The soil was a Greenleaf-Owyhee silt
loam ((fine-silty, mixed, superactive, mesic,
xeric calciargids) ). Previous crops were sudan
grass (1995-97 seasons) and potatoes (1998
season). Vandal hard red spring wheat was seeded
at 110 kg ha-1 with 17.8 cm row spacing. The
wheat
Methods continued- received uniform rainfall or
sprinkler irrigation through the boot to heading
stage. The IR treatments during grain filling
were imposed using a drip irrigation system.
Four drip lines were spaced 0.6m apart and
parallel to the planted rows in the 3.0m wide
main plots that received additional water during
grain fill. Different amounts of moisture were
applied during each drip irrigation set by
spacing emitters 30cm (full irrigation) or 60cm
(0.50 estimated ET) in the drip line. Bureau of
Reclamation (BOR) evapotranspiration estimates
from the Agrimet System were used to schedule
irrigations after heading. Baking quality
measures included flour protein (Fpro), flour
yield (Fyd), Mixograph peak time (Mpk), height
(Mht), tolerance (Mto), absorbance (Mab), bake
or loaf volume (Bvo), and Bvo/Fpro ratio (R).
Baking quality was determined using AACC method
No. 10-10B at the University of Idaho Aberdeen
Wheat Quality Laboratory. Bake volume was
determined using rape seed displacement. All
data were analyzed using analysis of variance
procedures available in SAS. Results Moisture
Received Water received uniformly as rain or
irrigation after May 15 was 5.1 cm in 95, only
1.5 cm in 96, 7.8 cm in 97, and 5.3 cm in 98. By
the end of the season, wettest and driest IR
treatments differed by 16.5, 32.6, 12.7, and 17.4
cm water for the 95, 96, 97, and 98 seasons,
respectively. IR treatments differed more in 96
because they were started earlier and there was
little rainfall during the rest of the
season. Grain Yield and Protein Grain yield
and crude protein were reported in greater detail
in a previous poster and are not shown here.
Briefly, water added at the 0.5ET rate during
grain fill increased yield in all seasons but the
full irrigation treatment was necessary for
maximum production in only 96 and 97. Yield
increased from as little as 28in 95 to as much
as 286 in 96 with additional water during grain
fill. Except for the 95 season, crude
protein declined as yield increased from the
first increment of added water. With a threefold
yield increase in 1996 with full IR, protein
decreased from 17.5 to 13. Crude protein
increased linearly in all years with each
increment of LSN, unless protein without LSN was
above 16. Baking Quality Baking quality
measures as affected by IR and LSN main effects
are shown in Tables 1 and 2. Flour Yield-
Avoiding moisture stress during grain fill
increased Fyd in three of four years. The higher
EN rate reduced Fyd in two years but LSN did not
affect Fyd. Fyd was affected no more than 2 by
treatments in any year but varied as much as 5.8
among years.
Summary The results suggest that stressing
wheat during grain fill is a poor strategy for
improving protein and baking quality as compared
to enhancing protein with LSN. Contrary to
previous concerns that LSN enhanced protein may
result in poorer protein quality, we found
protein quality surprisingly stable with
LSN. References 1. Stark, J. C., and T. A.
Tindall. 1992. Timing split applications of
nitrogen for irrigated hard red spring wheat. J.
Prod. Agric. 5221-226. 2. Christensen, N. W. ,
and R. J. Killorn. 1981. Wheat and barley
growth and N fertilization under sprinkler
irrigation. Agron. J. 73307-312. 3.
Sylvester-Bradley, R. 1990. Does extra nitrogen
applied to breadmaking wheat benefit the baker.
In Cereal Quality II Aspects of Applied Biology
No. 25, Association of Applied Biologists pp.
217-228.