Corn Early Nutrient Uptake and
Yield as Affected by In-Furrow
Fluid Potassium
Starter
Antonio P. Mallarino
Iowa State University
Fluid Fertilizer Foundation Forum
February 14-16, 2010
Plant Roots and P - K Uptake
 Relatively immobile nutrients, main
uptake mechanism is slow diffusion
through soil water to roots from a short
distance
 Actively growing large root system with
fine roots is key for P and K uptake
 Limited P and K uptake with
- cold, dry, compacted, or loose soil
- diseases and pruning by insects
Physiological-Root Growth Effects
 Fertilizing a fraction of the root zone
- Uptake compensation function
- Higher uptake per unit root surface
- Increased root growth/proliferation in
the zone and also outside the zone
 Reduced effects at high rates
- upper limits for uptake rate, salt
damage effects, crop differences
Fertilizer-Soil-Plant Interactions
 Does reaction with soil really decrease
P and K availability? If so:
- Banding increases uptake beyond
mass action flow, enhanced uptake
by unit root surface, induced root
proliferation
- This can compensate for a reduced
volume of fertilized soil and roots,
laterally or vertically
Residue Cover and Drought
 High residue cover
- In spring colder and wetter soil may
limit plant growth, P-K diffusion
- In summer increased water infiltration
and cover improves uptake efficiency
 Frequent dry surface soil
- Shallow roots are impaired and
subsurface placement can enhance P
and K uptake
Iowa P-K Placement Research
 Corn and soybean, granulated or fluid
fertilizers, side band, deep band, infurrow, for different tillage systems
 No consistent crop response to band P
 Corn response to deep-band K with
ridge-till, sometimes no-till or strip till
 Banding may be better at very low rates
and/or soil-test values that limit yield
and the efficacy of crop production
P & K Placement for No-Till Corn
Dry Fertilizer, 28 to 56 lb P2O5/acre, 35 to 50 lb K2O/acre
EARLY GROWTH
RELATIVE INCREASE (%)
140
NUTRIENT UPTAKE
PHOSPHORUS
GRAIN YIELD
POTASSIUM
135
130
PHOSPHORUS
125
120
115
110
105
PHOSPHORUS
POTASSIUM
POTASSIUM
100
CHECK
BROAD
DEEP
PLANTER
Mallarino, Bordoli, Borges, Barker (ISU)
Banding and Starter: Confusion
 What does “starter” mean?
- A small amount of fertilizer in the root
zone to supplement primary fertilizers
when needed, necessarily a band
 Fertilizer can be banded with planter
attachments or other tools. Can't apply
too high rates with the seed due to salt
effect and/or ammonia toxicity
 So banding in the furrow or in the root
zone may have a starter effect
Response to Starter P-K Alone
STARTER PK FOR NO-TILL CORN - 8 ON-FARM TRIALS OVER TWO YEARS
CHECK
STARTER
CORN YIELD (bu/acre)
200
NO PREPLANT PK APPLIED
NC
175
150
SW
NE
SE
SW
SE
SW
SE
125
100
75
VH
VL
L
VL
VL
SOIL-TEST P CLASS
L
L
L
Mallarino, ISU
Response to Starter After Broadcast
STARTER PK FOR NO-TILL CORN - 8 ON-FARM TRIALS OVER TWO YEARS
CHECK
STARTER
CORN YIELD (bu/acre)
200
WITH PREPLANT PK APPLIED
NC
175
NE
150
SE
SW
SW
SE
SW
SE
125
100
75
VH
VL
L
VL
VL
SOIL-TEST P CLASS
L
L
L
Mallarino, ISU
When is a True Starter Effect Likely?
 When an early plant growth delay can't
be offset during the season
 Applied nutrients aren't in the seedling
root zone (in topsoil or too deep).
 Cold and wet soil or disease/pests limit
early root growth and nutrient uptake
 Unlikely when broadcasting only once P
and K needed by corn and soybean, the
most common practice in Iowa
In-Furrow 3-18-18 Fluid Starter
Relative Increase (%)
100
Corn Early Growth
Early P Uptake
Broadcast: 100-140 lb P2O5 & K2O
80
Starter: 10-14 lb P2O5 & K2O
40
Broadcast
+ Starter
Broadcast
+ Starter
60
Starter
Broadcast
Starter
Broadcast
20
0
Relative Increase (%)
100
Early K Uptake
Corn Grain Yield
Broadcast
+ Starter
80
60
40
20
Broadcast
Starter
Starter
Broadcast
0
16 Iowa sites. Kaiser, Mallarino, and Bermudez, 2005
Broadcast
+ Starter
In-Furrow Starter N-P Sources
Corn Grain Yield
39 lb P2O5
8
Early Plant Growth
96 lb
P2O5
6
4
2
0
13 lb P2O5
9
24
3
9
24
3
10
34
0
MAP
10
34
0
Relative Increase (%)
Relative Increase (%)
10
75
39 lb P2O5
60
13 lb P2O5
45
30
15
9
24
3
13 lb P2O5
40
0
10
34
0
9
24
3
10
34
0
96 lb
P2O5
MAP
Relative Increase (%)
Relative Increase (%)
39 lb P2O5
9
24
3
96 lb
P2O5
MAP
Early P Uptake
60
20
10
34
0
0
Early N Uptake
80
10
34
0
9
24
3
39 lb P2O5
100
80
60
13 lb P2O5
9
24
3
40
20
9
24
3
10
34
0
10
34
0
0
Six Northern Iowa sites. Kaiser, Mallarino, and Bermudez, 2005
96 lb
P2O5
MAP
Relative Increase (%)
Fluid (2x2) N-P-K or N Starter
50
Early Corn Growth
Corn Grain Yield
NPK+N
40
N
30
NPK
20
10
NPK
N
NPK+N
Relative Increase (%)
0
50
Early N Uptake
NPK+N
N
40
NPK
30
Early P Uptake
NPK+N
NPK
N
20
10
0
Eight Iowa high-testing no-till sites. Mallarino and Bermudez, 2004
Starter P-K and Broadcast P
Early Corn Growth
Relative Increase (%)
70
STP
<16 ppm
P-K Starter: 5-25 lb P2O5 & K2O
60
STP
21-30
ppm
50
40
30
20
10
Corn Grain Yield
STP
16-20
ppm
P-K Broadcast: 100-160 lb P2O5,
100-180 lb K2O
P-K Starter + Broadcast
STP
> 30 ppm
STP
<16 ppm
STP
16-20
ppm
STP
21-30
ppm
STP
> 30 ppm
0
Mallarino, 2009
Response to Starter N, P, or K?
 Potentially higher early response to
increased N and P in the root zone than
for K
- K diffuses a greater distance than P
- Upper limit of early uptake rate/unit
root surface for K than for P, but
earlier root zone depletion
- More root proliferation for P than K
- Higher total plant uptake of K than P
In-Furrow Starter P-K and Starter K
 Conventional small plots, six trials
 Six treatments, four replications
- control, 3-18-18, 0-0-30, broad PK,
broad + 3-18-18, and broad + 0-0-30
 NAS 3-18-18 and NAS 0-0-30 applied at
10-14 lb of P2O5 or K2O/acre
 Broadcast PK: Current recs to apply
before corn of corn-soybean rotations
 Uniform N preplant and sidedressed
Corn Grain Yields by Site
220
Control
PK Starter
K Starter
PK Broadcast
PK Broad + PK Starter
PK Broad + K Starter
Corn Yield (bu/ac)
200
180
160
140
120
Field 4
Field 2
Field 5
Field 1
Field 6
Field 3
P4
K 82
P5
K 103
P 15
K 117
P 16
K 103
P 13
K 143
P 56
K 148
Average
Mallarino and Kaiser, ISU
Comparative Response Across Sites
Increase From Fertilizer (%)
60
Early Plant Growth
P Concentration
K Concentration
50
40
30
20
10
0
K
SP
SK BPK SPK *SK
B
B+
K
SP
SK BPK SPK *SK
B
B+
K
SP
SK BPK SPK *SK
B
B+
Mallarino and Kaiser, ISU
Comparative Response Across Sites
Increase From Fertilizer (%)
120
Early P Uptake
Early K Uptake
Grain Yield
100
80
60
40
20
0
K
SP
SK BPK SPK *SK
B
B+
K
SP
SK BPK SPK *SK
B
B+
K
SP
SK BPK SPK *SK
B
B+
Mallarino and Kaiser, ISU
In-Furrow Starter K Alone
 Eight replicated strip trials, 2 years,
managed with GPS, yield monitors, GIS
 Spit plot, 4 treatments, 3 replications:
- No K, broadcast K at 120 lb K2O/acre
- Split into no starter or NAS 0-0-30 at
15-22 lb K2O/acre
 Strip width 40 - 90 feet
 Strip length 960-2200 feet
Corn Grain Yield by Responsive Soil
240
Control
K starter
K Broadcast
BK + SK
Corn Yield (bu/ac)
220
200
180
160
140
120
Field 4
102
Field 6
130
Field 5
Field 3
Field 7
Field 1
155
180
214
236
Average
Bergmann, Mallarino, and Kaiser (ISU)
Comparative Response Across Sites
0
Early K Concentration
Early Plant Growth
B+SK
20
Increase from K Fertilizer (%)
-5
-10
SK
10
-15
BK
15
BK
B+SK
SK
5
-20
0
Grain Yield
Early K Uptake
20
20
15
15
BK
10
5
0
B+SK
SK
10
SK
BK
B+SK
5
0
Bergmann, Mallarino, and Kaiser (ISU)
Is There a True Starter K Effect?
 K has no true starter effect or is much
smaller and much less frequent than for
N and P
 Early corn growth response is a very
poor index of soil K deficiency and yield
response to K fertilization, "hidden
hunger" very often
 This doesn't mean that small starter K
rates may not be useful
Liquid Starter in High-Testing Soils
 The most clear comparative advantage
of small starter rates over broadcast
 Small probability of crop response, but
many farmers apply unneeded high
removal-based rates
 Small starter rates are sufficient to
catch any unlikely small corn response,
and much better for water quality
Liquid Starter with Optimum Test
 Low probability of small or moderate
crop response, maintenance based on
removal is recommended for long-term
profitability and reduced risk
 Starter or low broadcast rates catch any
response and is more profitable in the
short term, but will not maintain soil
test levels over time
 Flexibility, various options depending
on prices, land tenure, and philosophy
Liquid Starter in Low Testing Soils
 High probability of a large response,
broadcast fertilization and buildup is a
safe investment in most soils
 Starter rates usually don't apply enough
P and K. Why risk limiting yield?
 Very unlikely response to starter when
2-year rates are applied before corn
 May be a response to starter in some
conditions when "one crop rate" or
lower broadcast rates are applied
Within-Field Response Variation
80
Field 1
CORN
VL
Soil K Classes
Corn Yield Increase (bu/acre)
70
VL < 90 ppm
L = 91 to 130
O = 131 to 170
H = 171 to 200
60
50
Field 3
40
VL
L
30
Field 7
Field 5
Field 2
O
10
Field 6
Field 4
20
H
O
L O
H
L
VL
VL
L
O
H
Field 8
VL
VL
VL
L
L
L
L
OH
O
O H
0
Mallarino and Wittry, ISU
High Small-Scale Soil-Test Variation
Mallarino, 1996
Another Possible Role for Starter
 Much of the very small-scale variation
in many fields may not be fixed or
managed with large bulk dry fertilizer
applicators
 A small amount of liquid starter applied
across an entire field may be an
effective low-cost insurance to avoid
yield loss in small but perhaps frequent
field areas
Acknowledgements
 Early research (2000 - 2005)
- Nachurs/Alpine Solutions
- Agroculture Fertilizers
- Leopold Center for Sustainable Agriculture
 Recent research (2006 - 2009):
- Fluid Fertilizer Foundation
- Na-churs/Alpine Solutions
- International Plant Nutrition Institute