PHOSPHORUS UPTAKE BY SILAGE
CORN IN SOUTHERN IDAHO
Amber Moore, Steve Hines, Brad Brown, Mario
de Haro Marti, Christi Falen, Mireille Chahine,
Tianna Fife, Rick Norell, and Jim Ippolito
Introduction
• 545,000 dairy cows in Idaho
– Produce an estimated 12,000 tons of phosphorus
every year
– Applied to crops
• Corn silage – primary crop for P removal
– Greater P removal potential than wheat, beans,
potatoes, sugar beets, and other Idaho crops
– Feed for cows
Idaho OnePlan (NRCS)
recommendations
• Plans written from June 2007 to present
– Estimate P tissue 0.185 % P, based on NRCS plant
database
– For 32 ton/acre yield, estimate P removal at
41.4 lb P /acre, or 94.8 lb P2O5/acre
• Plans written prior to June 2007
– Estimate P tissue 0.260 % P, based on national
averages
– For 32 ton/acre yield, estimate P removal at 58.2
lb/acre, or 133.3 lb P2O5
Soil test P and nutrient uptake
• Increased soil test P may
– Increase potential for P removal, as has been seen in
triticale
– Induce Zn and Mn deficiencies, as has been seen in
high applications of P fertilizer
– Reduce Ca, Mg, and/or K uptake due to cation
competition
• Need to determine if these effects are occurring
– To account for them in the Idaho OnePlan software
– To help growers avoid potential toxicities and
deficiencies
Objective 1
• Estimate phosphorus removal by
irrigated corn silage crops cultivated
throughout Southern Idaho with
variable soil test P concentrations
Objective 2
• Identify effects of increasing soil test
P on potassium (K), calcium (Ca),
magnesium (Mg), zinc (Zn), and
manganese (Mn)
Site selection and description
• 42 corn silage fields sampled in 2008 and 2009
– Varying P fertilizer and manure application
histories
– 21 fields per year
– Sub-sampled 3 plots in each field
– Plot size - 2 rows X 10 ft.
Soil and tissue analysis
• Determine Olsen P of the soil at harvest
• Determine P, K, Ca, Mg, Zn, and Mn content of
the corn tissue at harvest
• Determine harvested yield of each plot
Why test soil P at harvest only?
• Our goal is to determine if P uptake in the
plant is influenced by the P content of the soil
• It was not our intent to look at a P budget
• Limited funds for study, could not afford to
sample fields more than once per season
Locations of corn silage fields in Southern Idaho selected for
sampling, by county.
# of fields sampled
County
2008
2009
Jerome
3
4
Twin Falls
4
4
Lincoln
3
2
Canyon
3
2
Cassia
3
2
Franklin
2
2
Gooding
2
5
Payette
1
0
Total
21
21
Yield and dry matter for corn silage harvested from 42 in 2008
and 2009 throughout Southern Idaho with varying fertilizer and
manure application histories. Soil test P varied from 3 to 300
ppm Olsen P.
Variable
Mean
Std. Dev
Minimum Maximum
Yield (wet
ton/acre)
31.7
7.0
15.7
47.2
Yield (dry
ton/acre)
11.2
2.6
5.2
17.4
% dry
matter
33.8
6.4
23.8
54.5
Whole plant tissue analysis for corn silage harvested from 21 fields in 2008
and 21 fields in 2009 throughout Southern Idaho with varying fertilizer and
manure application histories. Soil test P varied from 3 to 300 ppm Olsen P.
Tissue (ppm)
Mean
Std. Dev
Minimum
Maximum
P
2078
361
1163
3067
K
8885
2862
4385
16839
Mg
965
290
596
1660
Ca
1380
670
531
2791
Zn
12.7
4.1
6.2
27.3
Mn
24.7
12.0
8.5
57.2
B
4.6
1.8
2.5
12.4
Nutrient uptake for corn silage harvested from 21 fields in 2008
and 21 fields in 2009 throughout Southern Idaho with varying
fertilizer and manure application histories. Soil test P varied
from 3 to 300 ppm Olsen P.
Variable
Nutrient uptake (lb/acre)
Mean
Std. Dev
Minimum
Maximum
P
43.7
11.7
17.0
76.3
K
187
73.2
69.4
339
Mg
20.6
8.3
8.3
36.7
Ca
30.0
18.0
6.8
73.2
3500
y = 0.2276x + 2060.4
R² = 0.0009
Whole plant tissue P (ppm)
3000
2500
2000
1500
1000
500
0
0
20
40
60
80
100
120
140
160
180
200
220
Olsen P
Whole plant tissue P analysis related to Olsen P for corn
silage harvested from 21 locations in 2008 and 21
locations in 2009 throughout Southern Idaho.
P uptake recommendations
• Average P uptake – 44 lb/acre (for 32 ton/acre
yield)
• Average tissue P conc. – 0.21%
– 39 of 42 fields between 0.15 and 0.25%
– Over 20 ppm, increasing soil test P up to 200 ppm
with manure applications had not significant effect on
P removal
• Recommend Idaho OnePlan use 0.21% P for P
uptake estimates for newer and older plans
– 0.185 % - may be underapplying based on P uptake
– 0.260 % - likely overapplying based on P uptake
18000
Whole plant tissue K (ppm)
16000
14000
12000
y = -2.9768x + 8900.4
R² = 0.0031
10000
8000
6000
4000
2000
0
0
20
40
60
80
100
120
140
160
180
200
220
Olsen P
Whole plant tissue K analysis related to Olsen P for corn
silage harvested from 21 locations in 2008 and 21
locations in 2009 throughout Southern Idaho.
1800
Whole plant tissue Mg (ppm)
1600
1400
y = 0.0078x2 - 3.4621x + 1152.5
R² = 0.1241
1200
1000
800
600
400
200
0
0
20
40
60
80
100
120
140
160
180
200
220
Olsen P
Whole plant tissue Mg analysis related to Olsen P for
corn silage harvested from 21 locations in 2008 and 21
locations in 2009 throughout Southern Idaho.
3000
Whole plant tissue Ca (ppm)
silt, loam & silt loam
sandy loam & loamy sand
2500
2000
1500
y = -6.4411x + 1991.3
R² = 0.1529
1000
y = -2.4818x + 1233.5
R² = 0.09
500
0
0
20
40
60
80
100
120
140
160
180
200
220
Olsen P
Whole plant tissue Ca analysis related to Olsen P for
corn silage harvested from 21 locations in 2008 and 21
locations in 2009 throughout Southern Idaho.
Whole plant tissue Zn (ppm)
30
25
20
y = -0.012x + 13.395
R² = 0.0185
15
10
5
0
0
20
40
60
80
100
120
140
160
180
200
220
Olsen P
Whole plant tissue Zn analysis related to Olsen P for
corn silage harvested from 21 locations in 2008 and 21
locations in 2009 throughout Southern Idaho.
70
Whole plant tissue Mn (ppm)
silt, loam, and silt loam
60
loamy sand and sandy loam
50
40
y = -0.1275x + 38.259
R² = 0.219
30
20
10
0
y = -0.012x + 16.2
R² = 0.0108
0
20
40
60
80
100
120
140
160
180
200
220
Olsen P
Whole plant tissue Mn analysis related to Olsen P for
corn silage harvested from 21 locations in 2008 and 21
locations in 2009 throughout Southern Idaho.
Summary
• Recommend tissue P % for corn silage be
changed to 0.21 % in the Idaho OnePlan
• Identified potential trends of decreasing Mn, Ca,
and Mg with increasing Olsen P
• Identified possible soil texture affect on Mn and
Ca relationship to Olsen P
• Need controlled studies to further evaluate
relationships between soil test P, manure
application, soil texture, and nutrient
deficiencies/toxicities
Acknowledgements
• Dick Johnson – Idaho NRCS
• Anna Carey – Soils technician
• Josh and Jonathan Wisniewski – Dairy science
support
• UI Analytical Labs
• USDA ARS – Kimberly, Idaho
Thank you!
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Phosphorus uptake by silage corn in southern Idaho