1. Western Crop Science of America
Conference
June 10-13, 2013
Pendleton, OR
Olga Walsh
Assistant Professor, Soil Nutrient Management
Western Triangle Agricultural Research Center
Montana State University
Foliar Nitrogen Fertilizers in Wheat Production

2. Outline
 Literature review:
 Rationale
 Uptake Mechanisms
 Potential Benefits
 Efficiency
 MSU’s Foliar N study in spring wheat

3. Rationale for foliar application
Plants are known to attain water and
nutrients though foliage (Wittwer and Teubner, 1959)
Foliar is Beneficial/Potential when:
Soil applied nutrient uptake is limited due
to soil conditions (pH, soil moisture)
Significant potential for loss soil applied
nutrients (leaching, runoff)(Fernandez et al., 2013)

4. Foliar N products’ manufacturers claim
that foliar feeding increases NUE, saves
money, labor and time to wheat producers.
 Limited research on foliar fertilizers and
contradicting results
 Negative results – mainly due to leaf burn
Justification

5. Where does foliar fertilization fit
in?
 “Foliar fertilization can result in rapid
nutrient absorption and utilization to
correct deficiencies or to merely prevent
nutrient shortages during critical periods
of growth.
 However, unlike roots, plant leaves are not
adapted to assimilate large amounts of
nutrients and meet the bulk of the nutrient
requirement “ (IPNI, 2008).

6. 1. Adsorption (adherence to the leaf surface)
2. Movement through leaf surface
3. Absorption (cellular
compartmentalization)
4. Translocation and utilization by the plant
(Fernandez et al., 2013)
Mechanism sequence

7. Permeation studies:
 Leaf stomata (Below et al., 1984) facilitate the
mineral nutrient uptake
 Stomata size ~0.9 nm (Tyree et al. ,1990; Schonherr,
1976; Schonherr and Bukovac, 1979) - diameter of many
ions <0.8 nm in hydrated state facilitates
uptake
 Hydrophilic pores of the leaf cuticle (Barel and
Black, 1979) - depending on plant species, N
source, leaf side and aperture of stomata 6 -
62% of total N uptake (Eichert and Goldbach, 2008)
Mechanisms of foliar uptake

8. Foliar N – uptake efficiency
More efficient because many pathways
for N loss are avoided (leaching, runoff,
denitrification)
N is directly “fed” to the plant, the
available N is readily taken up, translocated
and utilized
Smaller amounts of N would be sufficient
to satisfy crop N requirements and to
effectively correct N deficiency mid-season
(Mosali et al.,2005)
N, P, and K are readily taken up via plant

9.  Huge range in literature: from 5% to 75%
depending on the crop and various factors
 Average for cereal crops ~30%
% N taken up through the
leaves
Crop/plan
t
N
source
% N taken up Reference
Bermuda
grass
Liquid
urea
24-57 Stiegler at al., 2009. Univ. of
Arkansas
Winter
wheat
UAN 30 Woolfolk et al., 2002. Oklahoma
State Univ.
Spring
wheat
UAN 28 Angus and Fischer., 1991.
Australia

10. Best Cond’s for Foliar
Applications
 Time of Day: late evening (after 6:00 p.m.)
and early morning (before 9:00 a.m.)
 Temperature: 65-85½ F; 70½ ideal
 Humidity: greater than 70% relative
humidity
 Temperature/Humidity Index: 140-160
 Wind Speed: less than 5 mph (Midwest

11. Things to consider
 Plant size and leaf area adequate for the
foliar sufficient uptake (midseason
application, crop is well established)
 Nutrients interaction: one nutrient may
enhance or inhibit the absorption of
another nutrient when applied together (Ling
and Silberbush ,2002)
 Foliar fertilisers likely to be cost effective
if price is no more than 15% greater than
N in urea (Angus, 2004)

12. Immediate response, prolonged flowering,
increased yields, enhanced growth during dry
spells, increased cold and heat tolerance,
increased pest and disease resistance,
maximized plant health and quality, improved
internal circulation of the plant
Most foliar products are highly compatible
with other chemicals (herbicides, pesticides),
easy to store and transport
Foliar N – potential benefits

13. Foliar N in wheat
 Objective - improved quality, increased
protein in wheat
 Increase in protein from 10.8% to 21% in
winter wheat (Finney et al., 1957); from 14.9% to
16.5% in winter wheat (Woolfolk et al., 2002)
 Most success – just prior to flowering
(Woolfolk et al., 2002) or immediately post
flowering (Gholami et al., 2011; Blandino and Reyneri, 2009)

14. Foliar N study in spring wheat
 Funded by MT Fertilizer Tax Advisory
Committee
 1st year of study, will continue for 2
more year
 3 locations (2 dryland and 1
irrigated)

15. Objectives
 To compare the efficacy of foliar N
fertilizers (UAN, liquid urea, and High
NRG-N) applied to spring wheat
 To determine the optimum N rate and
dilution ratio of foliar fertilizers and
the threshold at which spring wheat
grain yield is reduced due to leaf
burn

16. Protein Yield concept
 Spring wheat is produced for its quality,
represented by high grain protein content.
 Evaluating NUE in spring wheat should
take into an account both grain yield and
protein content.
 Combining yield and protein into protein
yield, as proposed by Jackson (1998)
makes sense because N is vital to both
yield and protein production.
 Protein Yield = grain protein content (%) * grain yield (lb ac-1)

17. PRODUCTS: UAN
 Urea Ammonium Nitrate (UAN)
 28-0-0 or 32-0-0, non-pressurized mix
of urea and ammonium nitrate
 Nitrate-N = quick response
 Ammonic-N = longer lasting response
 Sustained feeding from the water
soluble organic N in urea

18. PRODUCTS: LIQUID UREA
 Water-based urea solution (23-0-0)
Proposed benefits:
 Slower uptake by the plant
 Helps to maintains N levels within the
soil-plant system
 Application during the warm growing
months for rapid correction of N
deficiency

19. PRODUCTS: LIQUID UREA
 Dry urea is mixed with water to
produce liquid (15 to 23%) N by weight
 Dissolution is slow, product may
recrystallize (at below 60F)
 Filtering prevents nozzle clogging
 % of N is lower than in UAN,
transportation costs are normally
higher per unit of N (Jones et al, 2007)

20. PRODUCTS: high NRG-N
N and S (27-0-0-1) plus
Contains chlorophyll building elements
(Fe, Mg, Mn, Zn)
Reduced Salt Index - Less corrosive
than UAN solutions
Multi-forms of nitrogen - matches crops
demand curve
Lower application rates

21. Treatment Structure
Trt
Preplant N
Fertilizer
(urea) Rate, lb
N ac-1
Topdress N
Fertilizer Source
Topdress N
Fertilizer
Rate, lb N ac-1
Todress N
Fertilizer/Water
Ratio, %
1 0 - - -
2 80 UAN 40 100/0
3 80 UAN 40 66/33
4 80 UAN 40 33/66
5 80 LU 40 100/0
6 80 LU 40 66/33
7 80 LU 40 33/66
8 80 HNRGN 40 100/0
9 80 HNRGN 40 66/33
10 80 HNRGN 40 33/66

22. Applying foliar N fertilizers to spring wheat plots
using an ATV-mounted stream bar sprayer.
WTARC, Conrad, MT, 2012.

23. Results: Yield
Trt
Preplant
N
Fertilizer
(urea)
Rate, lb
N ac-1
Topdress
N
Fertilizer
Source
Topdress
N
Fertilizer
Rate, lb N
ac-1
Todress N
Fertilizer/W
ater Ratio,
%
Mean spring wheat grain yield,
lb ac-1
PATTON WTARC WARC
1 0 - - - 2256 (bcd) 4795 (c) 5022 (abc)
2 80 UAN 40 100/0 1893 (de) 5331 (ab) 5364 (abc)
3 80 UAN 40 66/33 1994 (cde) 5182 (bc) 5094 (abc)
4 80 UAN 40 33/66 1863 (e) 5209 (bc) 5666 (ab)
5 80 LU 40 100/0 2299 (bc) 5391 (ab) 4825 (c)
6 80 LU 40 66/33 2303 (bc) 5527 (ab) 4834 (bc)
7 80 LU 40 33/66 2399 (ab) 5539 (ab) 4949 (abc)
8 80 HNRGN 40 100/0 2511 (ab) 5692 (ab) 5728 (a)
9 80 HNRGN 40 66/33 2331 (bc) 5681 (ab) 5610 (abc)
10 80 HNRGN 40 33/66 2705 (a) 5757 (a) 5486 (abc)

24. Results: Protein
Trt
Preplant
N
Fertilizer
(urea)
Rate, lb
N ac-1
Topdress
N
Fertilizer
Source
Topdress
N
Fertilizer
Rate, lb N
ac-1
Todress N
Fertilizer/W
ater Ratio,
%
Mean spring wheat grain protein
content, %
PATTON WTARC WARC
1 0 - - - 13.8 (c) 10.8 (c) 13.4 (f)
2 80 UAN 40 100/0 17.2 (a) 12.8 (b) 14.4 (bcde)
3 80 UAN 40 66/33 16.8 (ab) 13.2 (ab) 13.9(def)
4 80 UAN 40 33/66 17.0 (ab) 13.1 (ab) 14.2 (cde)
5 80 LU 40 100/0 16.7 (ab) 13.2 (ab) 15.1 (a)
6 80 LU 40 66/33 16.8 (ab) 13.7 (a) 15.0 (ab)
7 80 LU 40 33/66 16.5 (b) 13.1 (ab) 14.9 (abc)
8 80 HNRGN 40 100/0 16.9 (ab) 13.1 (ab) 13.8 (ef)
9 80 HNRGN 40 66/33 17.1 (a) 13.2 (ab) 14.6 (abcd)
10 80 HNRGN 40 33/66 16.8 (ab) 12.9 (b) 14.0 (def)

25. Results: Protein Yield
Trt
Preplant
N
Fertilizer
(urea)
Rate, lb
N ac-1
Topdress
N
Fertilizer
Source
Topdress
N
Fertilizer
Rate, lb N
ac-1
Todress N
Fertilizer/W
ater Ratio,
%
Mean spring wheat protein yield
PATTON WTARC WARC
1 0 - - - 312 (d) 517 (b) 673 (b)
2 80 UAN 40 100/0 326 (d) 682 (a) 770 (ab)
3 80 UAN 40 66/33 336 (cd) 687 (a) 707 (ab)
4 80 UAN 40 33/66 317 (d) 684 (a) 805 (ab)
5 80 LU 40 100/0 384 (bc) 714 (a) 730 (ab)
6 80 LU 40 66/33 386 (bc) 755 (a) 723 (ab)
7 80 LU 40 33/66 395 (b) 723 (a) 735 (ab)
8 80 HNRGN 40 100/0 424 (ab) 743 (a) 788 (ab)
9 80 HNRGN 40 66/33 399 (b) 751 (a) 818 (a)
10 80 HNRGN 40 33/66 456 (a) 740 (a) 767 (ab)

26. Yield: 100% product to 0% water ratio
 When undiluted N products were used, the highest grain yields were
obtained with HNRGN at all 3 sites
 Supports the product manufacturer’s claim that HNRGN is less corrosive to
plant tissues compared to other liquid products, including UAN, due to its
lower free ammonia content and reduced salt index.
 The higher yield could also be the result of HNRG’s formulation which,
according to manufacturer, has been developed to minimize N loss and
2256 1893
2299 2511
4795
5331 5391 5692
5022 5364
4825
5728
1000
2000
3000
4000
5000
6000
Springwheatgrainyield,lbac-1 PATTON WTARC WARC
de
bc
ab
c
ab ab
ab
abc
abc
a
c
bcd

27. Yield: 66% product to 33% water
 At the ratio of 66% product to 33% water, both HNRGN and LU performed
better than UAN at dryland sites.
 Supports the suggestions that both HNRGN and LU are less corrosive and
that damage incurred due to foliar application of these products should be
lower compared to UAN.
 At the irrigated site – WTARC, however, grain yields were lower with LU,
compared to when UAN and HNRGN were used
2256 1994 2303 2331
4795 5182 5527 5681
5022 5094 4834
5610
1000
2000
3000
4000
5000
6000
Springwheatgrainyield,lbac-1
PATTON WTARC WARC
bcd bc bc
abc
bc
ab ab
abc abc
abc
bc
cde

28. Yield: 33% product to 66% water
 Similar to 66% product to 33% water dilution, when the solutions were most
diluted (ratio of 33% product to 66% water), at the irrigated site, LU resulted
in lower grain yields compared to UAN and HNRGN.
 On the other hand, at both of the dryland sites grain yields increased
significantly depending on product used as: UAN<LU<HNRGN
2256 1863
2399 2705
4795 5209 5539 5757
5022
5666
4949
5486
0
1000
2000
3000
4000
5000
6000
Springwheatgrainyield,lbac-1 PATTON WTARC WARC
bcd ab
a
bc
a
abc
ab abc
abc
e
ab
c

29.  Comparing protein by source at 3 different sites,
averaged over the 3 ratios.
Protein: N sources
17.0 16.6 17.0
13.1 13.3 13.0
14.1 15.0 14.1
10
12
14
16
18
UAN LU HNRGN
Grainprotein
content,%
Fertilizer N source
Patton WTARC WARC
a
b
a
a
a
b ab
a
b

30. Protein: N source
17.0
13.1
14.1
16.6
13.3
15.0
17.0
13.0
14.1
12
14
16
18
Patton WTARC WARC
Grainproteincontent,%
Fertilizer N source
UAN LU HNRGN
ab
b
a
a
a a
b b
a
 Comparing protein by site with 3 different N
sources, averaged over the 3 ratios.

31.  Comparing protein yield by source at 3 different
sites, averaged over 3 ratios.
Protein Yield: N Source
366 435 477
766 818 834852 817 886
0
200
400
600
800
1000
UAN LU HNRGN
ProteinYield
Fertilizer N source
Patton WTARC WARC
b
a
c
b
a a
a
a
a

32. Protein Yield: N Source
366
766
852
435
817 818
477
886 834
200
400
600
800
Patton WTARC WARC
ProteinYield
Fertilizer N source
UAN LU HNRGN
b
c
a
a
a a
a
b
a
 Comparing protein yield by site with 3 different
N sources, averaged over the 3 ratios.

33. Product to water ratio
 There were no significant differences in
yield, protein or protein yield associated
with product to water ratio at any of three
sites.
 In general, the highest yield, protein and
protein yield were achieved with the ratio
of 33%/66%, followed by 100%/0%, and the
lowest – at the ratio of 66%/33% at all three
sites.

34. Conclusions: Yield
Overall, due to LU and HNRGN’s lower
corrosiveness compared to UAN, even
when applied undiluted, LU and HNRGN
may be a better choice among the three
foliar products evaluated.
The cost of HNRGN at the time of
application was ~25% higher than cost of
LU, and almost 30% higher than cost of
UAN.

35. Conclusions: dryland vs
irrigated
 Preliminary results (one year of study, 3
site-years)
It is difficult to hypothesize why LU
performed worse at the irrigated site
compared to other products, and especially
compared to UAN.
If this trend continued in the next growing
season, it will be reasonable to suggest that
different products should be recommended
for dryland and for irrigated wheat
production systems.

36. Conclusions: Protein
Grain protein was maximized with LU at
the irrigated location, lower protein was
obtained with UAN and HNRGN. At
WTARC, similar trend was observed, but
the differences were not significant.
At Patton, grain protein increased as
LU>HNRGN>UAN.

37. Conclusions: Protein Yield
 Evaluating NUE in spring wheat should
take into an account both grain yield and
protein content.
At dryland sites, HNRGN resulted in a
combination of highest protein yield At the
irrigated site, the same trend was
observed, but the differences were not
significant.
The lowest protein yield at the dryland
sites was achieved with UAN, and with LU
- at the irrigated site.
 HNRGN resulted in superior grain yield,
and protein yield at all three experimental

38. THANK YOU!