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Nutrient Management of Forages and
Legumes
Crop Pest Management SchoolBozeman, January 6, 2010
by Clain Jones, Extension Soil Fertility Specialist
and Kathrin Olson-Rutz research associate
[email protected]; 994-6076
http://landresources.montana.edu/soilfertility
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Goals
1. To review use of Fertilizer Guidelines to
determine fertilizer N rates on forages
2. To present yield and economic responses of
pasture and hay to fertilizer
3. To provide an update on new fertilizer
products that could benefit forage producers
4. To illustrate some benefits of phosphorus,
potassium and sulfur on legumes and forages
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Do you or your clients grow forages?
Annual
Per
ennia
l
Both
None
0% 0%0%0%
1. 0 of 5
1. Annual
forages
2. Perennial
forages
3. Both
4. None
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How much N should be applied to alfalfa-grass stands?
Can use Fertilizer Guidelines for Montana Crops (EB 161)
Need to divide by fraction of N in fertilizer to find total
fertilizer need
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How much N should be applied to grass?
Fertilizer Guidelines for Montana Crops (EB 161):
http://www.montana.edu/wwwpb/pubs/eb161.html
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Single N application on dryland grass
pasture
• near Willow Creek, MT
• 0, 50, 100 lb N/acre spring broadcast
• harvested once
• dryland grasses
• Natv Bnch: Basin wldrye
• Natv Rhizom: Western whtgrs
• Hybrid Bnch: whtgrs (2), wldrye (4)
• Intro Rhizom: whtgrs (3)
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Single N application on dryland
grass pasture
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Yie
ld (
ton
s/a
cre
)
Willow Creek, MT, 1 year
lb N/ac applied once in springCarlstrom, Cash, and Ditterline 2003
0 50 100
Natv bnch (Basin Wldrye)
0 50 100
Natv rhiz(Wstrn Whtgrs)
0 50 100
Hybrid bnch (6)
0 50 100
Hybrid rhiz (3)
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First year marginal return as hay
-25
-20
-15
-10
-5
0
5
10
15
Marg
inal R
etu
rn a
s H
ay (
$/a
cre
)
50 100
Natv bnch (Basin Wldrye)
50 100
Natv rhiz (Wstrn Whtgrs)
50 100
Hybrid bnch (6)
50 100
Hybrid rhiz (3)
Willow Creek, MT, 1 yr harvest
lb N/ac applied once in spring
$375/ton urea, $80/ton hayCarlstrom, Cash and Ditterline 2003
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First year marginal return as forage
-45
-35
-25
-15
-5
5
Ma
rgin
al
Re
turn
as
Fo
rag
e (
$/a
cre
)
50 100
Natv bnch(Basin Wldrye)
50 100
Natv rhiz(Wstrn Whtgrs)
50 100
Hybrid bnch (6)
50 100
Hybrid rhiz (3)
Willow Creek, MT
lb N/ac applied once in spring
$375/ton urea, $15.75/AUM, 750 lb DM/AUM, 50% utilization
Carlstrom, Cash and Ditterline 2003
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Why would anyone fertilize
pasture?
Potential long term effect
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Single N application to dryland
grass pasture
• near Havre, MT
• 0, 50 and 100 lb N/acre fall broadcast once
• harvested for 6 years
• dryland grasses
• Natv Bnch: Basin wldrye, Beardless whtgrs, Green
needlegrs, Slender whtgrs
• Natv Rhizom: Thickspike whtgrs, Western whtgrs
• Intro Bnch: Crested whtgrs, Russian wldrye, Tall whtgrs
• Intro Rhizom: Pubescent whtgrs, Intermed whtgrs (2)
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Single 50 lb N application increases yields over
control on some grasses for several years
0
100
200
300
400
500
600
700
800
900
Natv bnch Natv rhizm Intro bnch Intro rhizm
Grass type and harvest year
Yie
ld d
iffe
ren
ce
ab
ov
e c
on
tro
l
(lb
/ac
re)
Havre, dryland grasses
single fall broadcast 50 N lb/acreLorbeer et al. 1994
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6
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Single N application increases
dryland grass yields
0
1
2
3
4
5
6
Natv bnch Natv rhizm Intro bnch Intro rhizm
6-Y
ear
To
tal
Yie
ld (
ton
s/a
cre
)
0 50 100 0 50 100 0 50 100 0 50 100
Havre, dryland grasses
single fall broadcast N lb/acreLorbeer et al. 1994
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First year marginal return on dryland
grass fertilization
-50
-40
-30
-20
-10
0
10
1s
t-Y
r M
arg
ina
l R
etu
rn o
n H
ay
($
/ac
re) Havre, dryland grasses
single fall broadcast N lb/acre
$375/ton urea, $80/ton hay
50 100
Natv bnch
50 100
Natv rhizm
50 100
Intro bnch
50 100
Intro rhizm
Lorbeer et al. 1994
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6-yr average annual marginal return
as hay
-10
-5
0
5
10
15
20
25
30
35
Natv bnch Natv rhizm Intro bnch Intro rhizm
6-Y
r A
ve
rag
e A
nn
ua
l M
arg
ina
l R
etu
rn
($/a
cre
/yr)
Havre, dryland grasses
$375/ton urea, $80/ton hay
single fall broadcast N lb/acre Lorbeer et al. 1994
50 100 50 100 50 100 50 100
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6-yr average annual marginal
return on forage
-6
-4
-2
0
2
4
6
8
6-Y
r A
ve
rag
e A
nn
ua
l M
arg
ina
l R
etu
rn
($/a
cre
/yr)
Havre, dryland grasses
$375/ton urea, $15.75/AUM
750 lb DM/AUM, 50% utilization
single fall broadcast N lb/acreLorbeer et al. 1994
50 100
Natv bnch
50 100
Natv rhizm
50 100
Intro bnch
50 100
Intro rhizm
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Under what situation would you advise N
fertilization?
Local
hay
market
Buying
hay
Intro
rhizom
grass
0% 0%0%
1. Only if there is a
local hay market
2. On any grass if
individual is also
buying hay
3. Only with introduced
rhizomatous species
1. 0 of 5
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Effect of N Rate on Irrigated Western
Wheatgrass, Blaine County
0
0.5
1
1.5
2
2.5
3
3.5
4
0 50 100 150 200
N rate (lb/ac)
Yie
ld (
t/a
c)
Christiansen, unpub. dataEconomics?
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QUESTIONS?
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Placement
• Granular: On established forage, surface broadcast is essentially only option. Others?
• Liquid (UAN; 32-0-0 or 28-0-0): Surface broadcast including fertigation, surface band, or knifed.
Method Forage Yield
Broadcast 2.9 t/ac
Knife 2.8 t/ac
Surface Band 3.4 t/ac
N. Central Regional
Extension Pub #326, KSU
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Foliar application
• Some N can be absorbed through leaves
• However, most foliar applied N ends up being
washed off and taken up by roots:
• Only 8-11% of foliar applied liquid urea was
taken up by leaves, whereas 37-67% of soil-
applied N was taken up by plant in same study
(Rawluk et al., 2000).
• Risk of burn? Likely not an issue due to low
rates applied (~25 lb N/t). Has anyone seen
grass ‘burn’?
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Timing
• Yield and quality are affected by timing
• Because urea may take days to weeks
to become available, urea should be
applied earlier than AN historically was
for fast green-up (AN simply dissolves,
UR requires a chemical reaction to
become available).
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Enhanced Efficiency Fertilizers and
forage production
• Forage production lacks incorporation, and plant
residue intercepts fertilizer, increasing chance for
volatilization
• EEFs retain N on site by reducing losses through:
• Stabilizing or inhibiting soil processes to extend N
availability (NSN®) or reduce urea conversion to ammonia
(Agrotain®: urease inhibitor – 14 days max) or ammonium
to nitrate (DCD)
• Slow release of urea through a coating (polymer coated –
PCU such as ESN®, sulfur coated - SCU)
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What is your experience with EEFs?
Never
hear
dH
eard
/no u
seU
sed o
nce
Used >
once
Recom
men
ded
0% 0% 0%0%0%
1. Never heard of them
2. Heard of them but
never used
3. Have used once
4. Have used more than
once
5. Have recommended
their use
1. 0 of 5
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Nitrogen EEF and forage production
• Can increase mid to late season cuttings
and protein, and encourage uniform
growth through season
• Can be blended with urea to meet goal
• Large early crop?
• Season-long forage or a late cutting?
PCU too slow, but urease
inhibitor can help reduce urea loss
Delayed release of PCU desirable
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• Allow application flexibility - e.g. fall
broadcast on coarse soil
• Are environmentally responsible but more $
• Are a Conservation Stewardship Program
enhancement
Enhanced Efficiency Fertilizers (EB0188) http://landresources.montana.edu/soilfertility
Go to Fertilizer Information
EEFs
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General considerations for dryland
grass N fertilization
• Species response to fertilization varies greatly
• Introduced and hybrid grasses tend to respond
more than native grasses
• A single moderate fertilization (50-100 lbs) may
increase production for several years
• Equal amounts of total N applied once or
annually over several years can yield the same
total production
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• Dryland grass pasture tends to hold N on
site and respond during wet years
• Protein and digestibility may improve with
N added
• Net economic gain as hay, but most likely
not as forage. What does this tell you?
Other considerations for dryland grass
N fertilization
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QUESTIONS?
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Phosphorus (P)
Why often deficient in Montana soils?
Binds with calcium to form poorly
soluble calcium phosphate
minerals
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Advantages of phosphorus (and potassium,
sulfur) fertilization on alfalfa-grass stand?
• Helps with N fixation in nodules
• Favors alfalfa over grass
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0
2
4
6
8
10
12
14
Geyser (6.2 ppm) Moore (5.2 ppm)
To
tal
4-y
r A
lfa
lfa
Yie
ld (
ton
/ac
re) 0-0-0-0
50-0-50-25
50-100-50-25
bb
a
ab
b
a
Location (Olsen P)
Single P application increases alfalfa
yield for several years
Wichman unpubl. data
One single application
Economics?
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• At $80/ton hay and $0.40/lb P, net revenue of P
fertilization = $22/acre/year
• At $80/ton hay and $1.20/lb P, net revenue of P
fertilization = $2/acre/year
P fertilization strategy
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P rate and source on alfalfa yield
0
1
2
3
4
5
6
7
0 P
MAP -
68
MAP -
138
APP -
68
APP -1
38 0 P
MAP -
95
MAP -
188
APP -
95
APP -
188
To
tal A
lfalf
a Y
ield
(to
ns/a
cre
)
2002Olsen P = 7.8 ppm (0-12 in.)
2003Olsen P = 4.0 ppm (0-12 in.)
Koenig et al. 2009 - Iron County, UT, 2 site-years
P rate = lb P2O5/acre
spring broadcast/sprayed
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Marginal return on P by rate
and source
-125
-75
-25
25
75
125
175
225M
AP
- 6
8
MA
P -
138
AP
P -
68
AP
P -
138
MA
P -
95
MA
P -
188
AP
P -
95
AP
P -
188
Ma
rgin
al R
etu
rn (
$/a
cre
)
2002Olsen P = 7.8 ppm (0-12 in.)
2003Olsen P = 4.0 ppm (0-12 in.)
Koenig et al. 2009 - Iron County, UT, 2 site-years
P rate = lb P2O5/acre, spring broadcast/sprayed
$400/ton MAP and APP, $100/ton hay
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P rate and source on yield
2002
yes
no
no
2003
yes
yes
yes
P > no P
MAP > APP
full P > 1/2P
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What to recommend to producers when $400/ton MAP
and $100/ton hay on a site with Olsen P < 8 ppm?
None Single
large
Small
annual
0% 0%0%
1. No application
2. Single large
application
3. Smaller annual
applications
1. 0 of 5
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How might your recommendation be
different when MAP is $1050/ton?
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Marginal return on P by rate
and source at high $ P
-125
-75
-25
25
75
125
MA
P -
68
MA
P -
138
AP
P -
68
AP
P -
138
MA
P -
95
MA
P -
188
AP
P -
95
AP
P -
188
Ma
rgin
al R
etu
rn (
$/a
cre
)
2002Olsen P = 7.8 ppm (0-12 in.)
2003Olsen P = 4.0 ppm (0-12 in.)
Koenig et al. 2009 - Iron County, UT, 2 site-years
P rate = lb P2O5/acre, spring broadcast/sprayed
$1050/ton MAP and APP, $100/ton hay
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Phosphorus fertilization considerations
• Low P soil should yield higher return on P
investment
• Yield response to P varies with growing
conditions
• On average, MAP is more economical
than APP, but not in every case
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QUESTIONS ON
NITROGEN OR
PHOSPHORUS?
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Potassium (K)
Needed in Montana?
Useful on many soils, even some
having high K values (especially in
spring due to cool temperatures)
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Which forages have largest K needs?
K removal amounts in forage crops
Crop Assumed Yield per Acre
K2O removal (lb/acre)
Alfalfa 2.5 t 150
Brome grass 1.5 t 95 Orchard grass 1.5 t 75 Timothy 1.5 t 94 Corn silage 20 t 167
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How might K, or lack of K, affect
an alfalfa-hay field?
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Factors decreasing S availability
1. Irrigated with low S in irrigation water
2. Sandy, acidic, or low organic matter
soils
3. Cold soils
4. Soils formed from minerals low in S or
far from industrial sources
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Sulfur (S)
Responses seen in alfalfa-grass fields?
Note: Yield increased 30% at Moccasin (See Fert. Fact 27)
Pro
tein
con
ten
t (%
)
Geyser
+S
-S+S
+S-S
-S
Moore Moccasin
Alfalfa-grass
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QUESTIONS ON
SULFUR?
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Special considerations for
grass fertilization
• If sub-irrigated fertilize for high yield potential
but apply P in fall
• On irrigated/wet meadows apply nutrients in
spring
• Split N generally does not increase total yield
• If seeding on fallow, OM >3% provides
adequate N for 2-3 years
• If N is banded or seed placed do not exceed
10-15 lb N/acre, also for P as ammonium-
phosphate
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Special considerations for
forage fertilization
• Broadcast most effective on perennial stands –
deep banding OK on old alfalfa stands
• Late fall/early spring for cool season mix (except
on sandy soil), mid-May for warm season mix
• In dryland consider ‘build up’ of P and K prior to
seeding
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Fertilization of annual legumes
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Do you grow or advise on annual
legumes for:
Fora
ge/h
ay
Seed
cro
pG
reen m
anure
Mix
None
0% 0% 0%0%0%
1. 0 of 5
1. Forage/hay
2. Seed crop
3. Green manure
4. A mix of the
above
5. Do not grow or
advise on annual
legumes
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Phosphorus and potassium uptake
NutrientPeas, Lentils,
ChickpeasWheat
Phosphorus (lb/bu) 0.67 0.62
Potassium (lb/bu) 0.87 0.38
P levels are often low in Montana (due to calcareous soils).
K levels are often moderate to high in Montana. No
research located on K and legumes in region.
BOTH P and K needed for N fixation!
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Effect of P on spring pea yield (2004-2005)
Sidney
10
15
20
25
30
0 17.5 35 70
P rate (lb P2O5/acre)
Gra
in Y
ield
(b
u/a
c)
Data from J. WaddellOlsen P = 10-14 ppm
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Montana phosphorus fertilizer
guidelines for annual legumes
Olsen P (ppm)
0 to 6 inches
Application rate
(lb P2O5/acre)
4 30
8 25
12 20
16 15
Above 16 0 up to crop removal** - Assume 2/3 lb P2O5 per bushel of grain
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Why are P fertilizer needs of annual legumes
somewhat less than for small grains and oilseeds?
• Lower yields
• Annual legume roots are shallower-
better able to take advantage of higher P
levels in upper 6 inches
• Legumes lower soil pH, mobilizing P
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Montana potassium fertilizer guidelines
for annual legumes
Soil Test K (ppm)
0 to 6 inches
Application rate
(lb K2O/acre)
100 35
150 30
200 25
250 20
Above 250 0 up to crop removal** - Assume 0.87 lb K2O per bushel of grain
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Fertilizer placement for legumes
• No nitrogen (N) or potassium (K) fertilizer
with the seed
• Small amounts of phosphorus (<10 lb
P2O5/ac) with the seed
• Ideal placement is below the seed
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Rooting patterns and starter and deep band
fertilizer placements
Wheat Legumes
Primary root
systems
Secondary root
system
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Conclusions
• Nitrogen, phosphorus, potassium, and sulfur can
all produce growth responses in Montana forage.
• Economic benefits often aren’t realized in the first
year (so don’t trust 1 year studies!).
• Soil testing is critical for determining fertilizer
needs.
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Questions?
Additional info at
http://landresources.montana.edu/soilfertility