Pasture Fertility
Glen Harris – UGA (Tifton)
50-10-40 lb.
N-P2O5-K2O
per ton
Exports
Hay Removes A Lot of Nutrients
Pastures Recycle Nutrients
Inputs
Nutrient Cycle
Exports
* fertilizer
* manure
* legumes (N)
* feed
* calves
* beef
Nutrient Removal
Crop
Yield
N-P2O5-K2O
Bermuda hay
8 tons
400-80-300
Corn grain
Corn silage
120 bu
16 tons
115-47-32
160-67-160
Peanuts
2 tons +
vines
60 bu
60 bu
240-39-185
Wheat grain
grain+straw
70-33-20
100-40-122
Fescue pasture 300 lb. beef
9-7-1
Bahia pasture
6-5-1
200 lb. beef
UGA Fertilizer Recommendations
(Medium Soil Test P and K)
Hay
400-60-200
Pasture
175-40-40
Hay Production – 2008
Cost Breakdown – C. Lacy
15%
2%
3%
1%
3%
8%
70%
Fertilizer
Interest on Var. Costs
Labor
Lime
Fuel & Repairs
Pesticides
Fixed & Mgmt Costs
Fertilizer Prices (cents/lb)
90
80
70
60
Pre=2005
2008
2009
2010
2011
2012
50
40
30
20
10
0
N
P2O5
K2O
Basics of Soil Fertility for
Forages
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•
•
•
Nitrogen
pH and Liming
Potassium
Soil Testing
Comparing Nitrogen Fertilizers
Nitrogen Source
Comments
Anhydrous Ammonia (82%N)
Gas
Safety/Dealer Insurance
Methamphetamines
UAN Solutions (28-32%N)
Liquid
Urea+Ammonium+Nitrate
Urea (46%N)
Solid
Concentrated
Volatilization
Ammonium Nitrate (34%N)
Solid
Regulations/Availability
Ammonium Sulfate (21%N)
Least Concentrated
Acidifying
Nitrogen Fertilizers Sold in Georgia - 2010
X 1000 tons
250
234
200
150
100
63
50
0
20
25
AS
AN
2
AnyH
Urea
N Soln
Enhanced Efficiency Fertilizers
For Cotton in the Southeast
Glen Harris
UGA - Tifton Nutrisphere -N
“Enhanced Efficiency (EE)” Fertilizers
New Term Coined by The Fertilizer Institute (TFI)
“…products that minimize the potential of nutrient loss to the environment.”
Slow/Controlled Release
Absorbed
Coated
Occluded
Reacted
CoRoN
Stabilized/Additive
Urease Inhibitors
Nitrification Inhibitors
Stabilizers
Humates
Nutrisphere – N (?)
Association of American Plant Food Control Officials (AAPFCO)
Fertilizer additive that inhibits
degradation of urea by urease
(NBPT)
“Agrotain Plus” (for UAN liquids)
– also includes a nitrification
inhibitor (DCD)
Does not affect microbes
(or other soil organisms) directly
Reduces loss of surface applied
urea-N to volatilization (up to 14
days under drying conditions)
and reduces nitrate leaching
Specialty Fertilizer Products
through Southern States
Polymer “Nutrisphere”
technology
Active Ingredient =
“40 % maleic-itaconic copolymer”
Claims Urease + Nitrification
Inhibition
Mode of action = “shields” N
from Nickel for urease and from
microbes for nitrification
(documented ?)
Understanding Current Fertilizer Alternatives
Volatilization and Nitrification
Volatilization = Urea ----- Ammonium (NH3) gas
Nitrification = Ammonium (NH4+) --- Nitrate (NO3-)
Forms of Nitrogen
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•
•
•
Ammonia – NH3 (gas)
Ammonium – NH4+
Nitrate – NO3Urea – CO(NH2)2
Composition of Ammonium Nitrate (34%N)
50%
Nitrate (NO3)
50%
Ammonium(NH4)
Composition of Urea (46%N)
100%
100%
Urea
Composition of UAN (32 – 28 % N)
25%
50%
25%
Urea
Ammonium(NH4)
Nitrate (NO3)
Composition of “19-E” (19 – 18 %N)
41%
59%
Nitrate (NO3)
Ammonium(NH4)
Composition of 24-0-0-3(S)
(Urea+Ammonium Nitrate+Sodium Nitrate)
30%
35%
35%
Urea
35%
Ammonium(NH4)
Nitrate(NO3)
Materials and Methods
Volatilization
• Closed Chambers
• 6 inch diameter PVC with cap
• Acid Trap analyzed for NH4-N after 7 days
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•
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•
Treatments:
Solids: Urea, NSN, Agrotain
Liquids: UAN, NSN, Agrotain Plus
UTC
N Volatilization – Cotton, 3 Location Average
50
48
49
45
40
35
NH4
mg/L 30
25
20
15
15
10
5
0.3
0
Urea
NSN
Agrotain
Control
N Volatilization – Forages, 2 Location Average
Dr. Dennis Hancock – University of Georgia, Athens
140
132
128
120
100
NH4
mg/L 80
60
2008
2009
59
46
44
40
23
20
1.75 0.1
0
Urea
Agrotain
NSN
Control
Dr. Dennis Hancock – UGA, Athens
‘Russell’ Bermuda Grass Yields (lbs DM/a) - 2008
19291
20000
17302
18000
16000
14000
12000
10000
8490
8908
8704
8000
6000
4000
2000
0
Eatonton
Urea
Calhoun
Agrotain
NSN
16985
Dr. Dennis Hancock – UGA, Athens
‘Russell’ Bermuda Grass Yields (lbs DM/a) - 2009
17525
18000
16464
16000
14955
14000
12000
10730
11431
10226
10000
8000
6000
4000
2000
0
Eatonton
Urea
Calhoun
Agrotain
NSN
Dr. Dennis Hancock – University of Georgia,
Athens
Agrotain Treated Urea
as compared to urea applied in the same
way (averaged over 4 site-yrs):
• Reduced ammonia volatilization by
over 63%.
• Produced 11% more forage yield.
• Recovered 19% more of the applied N
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•
•
•
•
Agrium Company
ESN = Environmentally Smart Nitrogen
Polymer Coated Urea
Company = Agrium
“Controlled Release” (not “slow release”
?)
• “Releases as the Soil Warms”
• Slow Release vs. Split Applications
The Value of Litter
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Pre 2005 Prices
60# N x .28 x .6 = 10.08
60 # P2O5 x .22 x .8 = 10.56
40 # K2O x .12 x .8 = 3.84
» Total = $24.48
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•
•
•
2008 Prices
60#N
x .85 x .6 = 30.60
60#P2O5 x .85 x .8 = 40.80
40#K2O x .80 x .8 = 25.60
» Total = $97.00
» 2013 Prices
• 60#N
x .72 x .6 = 25.92
• 60#P2O5 x .55 x .8 = 26.40
• 40#K2O x .52 x .8 = 16.64
» Total = $68.96
Other Nutrients ?
Organic Matter ?
Liming ?
Nematode Suppresion ?
Why Lime?
Nutrient Availability
Nutrient Unavailability
Provide Ca and Mg
Nitrogen Fixation
Biological Activity
Source: Foth and Ellis
Soil Fertility
Calcitic and Dolomitic Lime
(x 1000 tons)
Magnesium Ratings for Forages
( Coastal Plain Soils - lb/a, Mehlich 1)
*Low = 0 – 30
*Medium = 31- 60
High = 61 +
From The Soil Test Handbook for Georgia” :
“If soil test magnesium is low,
use dolomitic limestone” !
K is for Persistence !
Deficiency
Weeds
Winterkill
Loss of
Stand
K is for Persistence !
Deficiency
Weeds
Winterkill
Loss of
Stand
N with no K can kill a stand in 2 year
Questions ?