1. Forage Fertilization 29 March 2018 Eastern Oklahoma Beef Cattle Summit
Nathan Slaton
Professor, Soil Testing
Assistant Director, Agricultural Experiment Station
29 March 2018
Eastern Oklahoma Beef Cattle Summit

2. Tools You Can Use on Phone or Computer
WebSoil Survey
SoilWeb Ap for Smart Phone
IPNI Nutrient Removal Calculator

3. Topic Outline Lime Nitrogen Potassium Particle size & effectiveness
Pelleted lime vs ag lime
Effect of N fertilizer source and rate on pH
Nitrogen
Productivity without N
N sources and urease inhibitors
Potassium
Why, how and when K is needed!

4. Lime Fundamentals Source & Quality Lime basics Sources
Soil test regularly
Know your lime source
Incorporate when possible
Forage establishment
Don’t wait too long!
Subsoil acidity
Sources
Ag Lime
Pelleted lime
Poultry litter

5. Relative Effectiveness Avg Relative Effectiveness
Effectiveness of Lime
Particle Size
Soil pH after 1 year
Relative Effectiveness
Avg Relative Effectiveness
Calcitic
Dolomotic
mesh pH %
avg
No lime
5.0
4-8 5 8
20-30
5.6
5.5 54 39 47
40-50
5.9
5.8 74 65 70
60-80
6.3
6.2 96 84 90
100
6.5
6.6
Source: University of Idaho Pub #CIS0787, R. Mahler

6. Pelleted Lime vs Ag lime
Pelleted lime often marketed as being much more effective than ag lime – NOT TRUE
Typically
Little, if any, difference in
Purity
Reaction speed
Pelleted lime has advantage of smaller size, but disadvantage of binding agent
Pelleted lime usually has a higher ECCE score
BUT equivalent rates are usually only a few hundred pounds apart (See example on next slide)

7. Lime Quality – Compare $ources
Overall
Quality Score
Lime Purity
Lime Source
CCE†
Fineness Factor Information‡
ECCE§
Equal Rates¶
10 mesh
60 mesh
100 mesh
Fineness Factor
- - - lb/acre - - -
Ag lime
91%
93%
44%
32%
62.4
56.8
2,000
Pelletized lime
80%
100%
100.0
80.0
1,420
†CCE, calcium carbonate equivalent.
‡The values in each column represent the percentage of material passing through a 10, 60 and 100-mesh sieves. Fineness factor coefficients of 0, 0.4, 0.9 and 1.0 are multiplied by the percentage of lime having a diameter of >10-mesh (7%), <10-mesh and >60-mesh (49%), <60-mesh and >100- mesh (12%) and <100-mesh (32%) were used to calculate the fineness factor.
§ECCE, effective calcium carbonate equivalent, is the product of [fineness factor x (CCE/100)].
¶Equivalent rates, the amount of lime needed from each source to neutralize the same amount of acidity. Calculated by [((Ag lime ECCE/pelletized lime ECCE) × 2,000 lb ag lime/acre) = lb pelletized lime/acre]
Source: Arkansas Soybean Handbook, Chapter 5

8. Lime Rate on Captina Silt Loam
Ag Lime rate
ECCE
Water pH
Salt pH
Jan 2007
April 2007
Dec 2007
Feb 2008
Jan
2007
April
Dec
Feb
2008
lb/acre
Soil water pH
Soil Salt pH --
5.5
5.4
5.1
5.2
4.8
4.3
4.5
1250 56
5.0
4.4
4.7
2500
5.7
5.8
5.9
5.3 90
6.0
4.6
5000
6.4
6.1
56.3 ECCE for Mixture & 90 ECCE for Fines. Soil sample depth was 4 inches
Lime applied in January 2007 and sampled in April and December 2007 and February Ag lime obtained from bulk lime pile in at Coop in Morrilton, AR
5000 lb Ag lime was UA recommendation.

9. Soil pH – Seasonal Variability
5.7 (high pH)
5.4 (mean pH)
5.1 (low pH)
Source: Keogh and Maples, 1972 (AES Bull. #777)

10. Effect of N rate/source on Soil pH
Effect of N Source
(applied at 360 lb N/A)
Effect of Annual N Rate
Captina silt loam, After 2-years of N fertilization

11. Bermudagrass Response to N
2-yr study
4-yr study
2-yr study

12. Summary of Bermudagrass Yields Receiving no N-fertilizer
Irrigated
Non-irrigated
ton/acre #
%RY
<1 1 8 5 10
1-2 3 18 26
2-3 4 39
3-4 37 2 52
4-5 77

13. Bermudagrass Response to N Rate
No N yield range
1520 to 5940 lb DM/acre
80% Yield 274 lb N/acre
90% Yield 364 lb N/acre
Maximum yield across sites was 7.5 ton/acre.
Source: Seay and Slaton (2008, Forage & Grazinglands)

14. N Source Preferences Urea UAN NH4NO3 Ammonium Sulfate
5 to >20% of N loss via NH3 volatilization (typical)
Apply to dry forage/soil
Often cheapest per unit of N
UAN
Assume one-half of N loss from urea
NH4NO3
Best forage N-fertilizer, if available and priced right
Ammonium Sulfate
Use to supply part of N where S deficiency occurs
Controlling/Reducing Loss with Urea or UAN
Apply before rain
Amend with urease inhibitor
Only NBPT-containing inhibitors are recommended (e.g., Agrotain, Arborite, Factor, N-Fixx, etc…)

15. N-Fertilizer Additives
What are they?
Nitrification inhibitors
Delay conversion of NH4-N to NO3-N
Probably not needed for actively growing forage
Urease inhibitors
Delay conversion of urea to NH4-N and reduce ammonia loss (NH3) when conditions are favorable
Use with surface-applied urea or UAN.
Urease inhibitors
From a few to many products in past 10 years
Should you use one?
Check for NRCS incentives
Depends on conditions and N source

16. Urease inhibitor reduces N loss from urea (or UAN)
Ammonia Loss
No NH3 loss from NH4NO3
Urease inhibitor reduces N loss from urea (or UAN)
Majority of Urea-N loss occurs in first 2 to 3 days.
Need 0.25 to 0.5 inch of rain within 24 to 36 hours after application to incorporate.
Rain at 72 hours is too late…
N loss becomes worse as temps increase
Source: Massey (2007) Captina silt loam

17. Agrotain for Urea – 2007 Captina soil
N rate
NH4NO3
Urea
Urea+Ag
PPL
lbs N/A
lbs forage/A
4617
45 x 2
8151
7647
7537
6764
60 x 3
10120
9389
9168
7758
90 x 3
11718
10429
10259
9235
120 x 3
11017
10983
11012
10821
150 x 3
12528
11578
11994
12076
LSD0.1
766

18. Urease Inhibitor Benefits Use in Bermudagass Hay Production
Fertilizer
Yield Total
Calhoun 2008
Calhoun 2009
Eatonton 2008
Eatonton 2009
Tons hay/acre/season (4 total cuttings)
Ammonium Nitrate
10.1 a
9.6a
5.1 a
5.9 a
Urea
8.7 cd
7.5 cd
4.2 b
5.4 ab
Urea+NBPT
9.7 ab
8.8 ab
4.5 ab
5.7 a
Urea+Nutrisphere
8.5 cd
8.2 bc
4.4 ab
5.1 b
UAN
9.5 ab
7.8 bcd
5.5 ab
UAN+NBPT
9.6 ab
7.0 d
4.8 ab
5.2 b
No N
5.0
5.2
1.3
1.1
University of Georgia (Connell et al., 2011; Crop Sci.)
N applied in two-split applications of 150 lb N/acre at spring greenup and after 2nd harvest.
Site pHw ranged from 6.2 to 6.9.

19. Urease Research Summary
Urease inhibitor NBPT applied to urea granules or UAN sometimes increase bermudagrass yield as compared to untreated urea.
Forage fertilized with NH4NO3 tended to produce highest overall yields.
Poultry litter, 50 to 70% N equivalence to inorganic fertilizer-N.

20. N Sources for Tall Fescue mid-March N (75 lb N/acre)
Comparison
Mt Vernon, MO
Columbia, MO
2006
2007
2008
% Yield Difference (Urea as standard)
Urea vs NH4NO3 4 8 16 14 2
Urea vs Urea+AS -3 7 19 -7
Urea vs Urea+NBPT 5 21
<1
Urea vs no N
-46
-55
-50
-58
-54
Urea Yield (lb/acre)
7779
3680
3139
4037
4716
Source: Univ. Missouri
Bold red Values Indicate a significant difference at P=0.20
Positive values indicate urea yielded less than compared N source
% Difference Calculation = [(N Source – Urea)/Urea] x 100

21. Nitrogen Sources for Tall Fescue mid-August N (75 lb N/acre)
Comparison
Mt Vernon, MO
Columbia, MO
2005
2006
2007
% Yield Difference (Urea as standard)
Urea vs NH4NO3 55
-13 -6 28
Urea vs Urea+AS 1 -3
<1 4
Urea vs Urea+NBPT 22
-15 18
Urea vs no N
-61
-70
-78
Urea Yield (lb/acre)
1245
2201
2865
1935
Source: Univ. Missouri
Bold red Values Indicate a significant difference at P=0.20
Positive values indicate urea yielded less than compared N source
% Difference Calculation = [(N Source – Urea)/Urea] x 100

22. Tall Fescue N Summary Spring/Greenup Application
Urea & ammonium nitrate yields same in 3 of 5 years
NBPT benefit only 1 of 5 years
Positive yield response to ammonium sulfate was likely from N loss rather than S
Late Summer/Fall Application
Ammonium nitrate yields greater than Urea in 2 of 4 years
Benefit from NBPT treated urea tended to be more common in fall (August application) than spring

23. Forage Needs POTASH

24. Forage Nutrient Removal
P2O5
K2O
IPNI Values
lb nutrient/ton
Bermudagrass 46 12 50
Fescue 37 54
Ryegrass 43
Bahiagrass 35
Arkansas Database Values
Bermuda (ARK) 44 13
Fescue (ARK) 14 51
IPNI Nutrient Removal Calculator,
Davis (2000, AES Research Series #478)

25. P and K Value: Bermudagrass Hay
Nutrient
Unit
Content
Fertilizer
Fertilizer Price
Value
lb P2O5/ton
$/unit
$/ton
Phosphorus 13
DAP,
0.47
6.11
Potassium
lb K2O/ton 50
Potash,
0.28
14.00
Sum (P and K)
$20.11
Fertilizer Prices from
$436/ton diammonium phosphate
$335/ton potash
$361/ton urea

26. Soil-Test K and K Fertilizer Rate Bermudagrass Hay
Seay and Slaton (2008)

27. Soil-K Depletion Rate Bermudagrass hay
Soil K depletion appears to be quadratic rather than linear for this system with large K removal and inputs. Do soils have an low equilibrium threshold for K? This has been suggested in the literature.
Bermudagrass hay

28. K-Fertilizer Rate & Bermudagrass Hay Yield

29. Bermudagrass Yield Response to K
K rate
5-yr Avg Yield
% of Max
lb K2O/A
Ton/A/yr %
3.4 51
100
5.0 75
200
5.9 88
300
6.1 91
400
6.4 96
500
6.7
Slaton et al. ( , AAREC)

30. Soil Test K and Bermuda Forage Yield
Potential for yield loss when soil-test K is <120 ppm and no K is applied
Stand loss may/will begin if K is inadequate.
Sufficient K helps plants assimilate nitrate
Soil samples collected from 0-4 inch depth

31. Forage NO3-N and Potassium
High NO3-N content of forage may be a sign of K deficiency
Crude protein content of forage may also be higher in K-deficient forage
Brown leaf spot is a sign of K deficiency
Forage nitrate (ppm)

32. Luxury Uptake of K by Forage
K Sufficient
Source: Slaton et al. (2011, AES Research Series 588)
Data from 5th year of fertilization and cropping

33. Luxury Uptake of K by Forage
K Sufficient
Source: Slaton et al. (2011, AES Research Series 588)
5th year of annual fertilization and cropping

34. Relationship of Forage RFV and Potassium Average RFV of 987 Bermuda Samples Grouped by Forage K Level : “Quality Forage” Program:
*Each bar represents average RFV for all samples within the forage
K level group shown, when K is averaged in increments of 0.20%
Source: Robert Seay (CEA-retired), Benton County, AR

35. K Fertilizer Management Summary
Soil test routinely
Avoid Luxury Consumption
Split apply the K
Blend with N
Close to a 1:1 N:K ratio
Monitor nutrient balance
K input – Crop K removal

36. Thanks for Your Attention
Questions??

38. Cool-Season Grass & N Late summer and fall fertilization
Apply lb N/acre N from mid-August to early September to stimulate growth for grazing, hay or stockpiling
Late-winter or early-spring fertilization
Apply lb N/acre at first sign of greenup usually in early to mid March
For intensive hay management apply N after first hay cutting if moisture and temperatures are suitable
Figure Source: Murdock (1982, Univ. Kentucky)

39. Critical Humidity & Urea Ammonia Loss
Moisture moves from air to urea
Moisture moves from urea to air
Slide from Dr. David Kissel, Univ. Georgia

40. Luxury Uptake of P by Forage
Source: Slaton et al. (2011, AES Research Series 588)
Data from 5th year of fertilization and cropping

41. Luxury Uptake of P by Forage
Source: Slaton et al. (2011, AES Research Series 588)
5th year of annual fertilization and cropping

42. Agrotain for Urea – 2007 Johnsburg soil
N rate
NH4NO3
Urea
Urea+Ag
PPL
lbs N/A
lbs forage/A
6224
45 x 2
9583
8591
9063
7339
60 x 3
10438
9437
10173
8651
90 x 3
10316
10027
10353
9575
120 x 3
11045
10432
10628
10558
150 x 3
11372
11053
10848
10466
LSD0.1
628

43. Biostimulents, Fertilizer Additives, and Alternative Fertilizers
Product that stimulates plant physiological processes, ‘stress gene’ stimulents, or contains hormones, microbes, humic acids, etc…
Usually applied at low rates
Fertilizer Additives
Urease and nitrification inhibitors
Biostimulents (see above)
Polymer coatings (some good & some bad)
Alternative fertilizers
Manures & biosolids
Other products (e.g., liquid poultry litter)

44. Relationship of Forage Crude Protein and Potassium Average CP level of 987 Bermuda Samples Grouped by Forage K Level “Quality Forage” Program:
*Each bar represents average CP for all samples within the forage
K level group shown, when K is averaged in increments of 0.20%
Source: Robert Seay (CEA-retired), Benton County, AR

45. Relationship of Forage TDN and Potassium Average TDN of 987 Bermuda Samples Grouped by Forage K Level “Quality Forage” Program:
*Each bar represents average TDN for all samples within the forage
K level group shown, when K is averaged in increments of 0.20%
Source: Robert Seay (CEA-retired), Benton County, AR