Baking Quality Response to Late Season N with Variable Moisture During Grain Fill. K. O’Brien, B. Brown, and R. Gibson. University of Idaho

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 (<14%).

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.

ResultsMoisture 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 28%in ‘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.

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).

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.

References1. Stark, J. C., and T. A. Tindall. 1992. Timing

split applications of nitrogen for irrigated hard red

spring wheat. J. Prod. Agric. 5:221-226.

2. Christensen, N. W. , and R. J. Killorn. 1981.

Wheat and barley growth and N fertilization under

sprinkler irrigation. Agron. J. 73:307-312.

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.

Table 1. Late season water effects on Vandal hard red springwheat baking quality. 1995-98.

ET Fpro Fy Mpt Mh Mt Ma Bv R% % % cm3 cm3/%

19950 14.2 70.4 4.18 6.73 71.4 66.3 976 68.80.5 15.0 70.3 2.88 6.62 61.5 68.0 1056 70.71.0 14.8 70.2 3.28 6.60 65.6 67.8 1045 70.7

*** ns *** ** *** *** *** *

19960 15.7 67.8 4.44 6.94 70.5 68.2 1092 69.90.5 12.9 69.3 4.23 6.67 72,8 63.2 991 77.01.0 12.3 69.3 3.96 6.34 73.7 62.4 977 79.8

*** *** ns *** * *** *** ***

1997.0 13.3 67.8 4.08 7.18 72.4 61.9 1148 86.90.5 12.6 69.3 3.75 6.80 72.3 61.4 1145 91.41.0 13.0 69.9 3.53 7.01 67.4 61.8 1167 90.2

* *** ** ** *** ns ns *

19980 14.3 62.1 4.76 6.67 76.0 60.4 1213 84.90.5 12.6 64.6 3.62 6.26 75.8 57.3 1138 90.31.0 13.0 64.6 3.98 6.12 76.6 58.2 1194 91.8

*** ** ** ns ns ns * *ns, *, **, *** refer to nonsignificant , and significant at the 10, 5, and1% probability levels, respectively.

Table 1. Late season nitrogen effects on Vandal hard red springwheat baking quality. 1995-98.

LSN Fpro Fy Mpt Mh Mt Ma Bv Rkg ha-1 % % cm3 cm3 %-1

19950 14.3 70.3 3.43 6.58 67.3 67.1 1004 70.445 14.8 70.4 3.52 6.65 65.5 67.6 1037 70.390 14.9 70.1 3.39 6.72 65.8 67.5 1037 69.5

*** ns ns ns ns ns *** ***

19960 13.2 68.6 4.28 6.63 73.8 63.8 999 76.845 13.7 68.9 4.29 6.59 72.3 64.6 1021 75.390 14.0 68.8 4.07 6.75 71.1 65.4 1040 74.6

*** ns ns ns ** *** ** **

1997.0 11.9 68.9 4.13 6.53 74.5 60.5 1090 92.245 13.0 69.2 3.67 7.04 69.4 61.9 1170 90.290 14.0 69.0 3.56 7.43 68.2 62.7 1200 86.1

*** ns *** *** *** *** *** ***

19980 12.6 64.2 4.11 6.47 76.9 57.2 1122 89.245 13.4 63.6 4.08 6.24 76.5 58.9 1195 89.690 14.0 63.4 4.18 6.33 75.1 59.8 1230 88.2

*** ns *** *** *** *** *** ***ns, *, **, *** refer to nonsignificant , and significant at the 10, 5, and1% probability levels, respectively.