1. Corn Yield Response to Starter P Fertilizer and ‘Avail’ P Fertilizer Enhancer Ron Gehl Sheri Cahill Deanna Osmond Dept. of Soil Science NC State University SSSNC Annual Meeting 2010

2. Average Soil Test Phosphorus
70% medium or above

3. Soil Test Phosphorus: Corn/Soybean Rotation

4. Starter P as a Corn Management Option
In some geographic regions, starter P has been shown to increase crop yields even when STP is relatively high
Response dependent on field management, early-season weather, field issues
P availability a concern in many NC soils – need verification of crop response to starter P in NC cropping systems and soils
‘New’ products currently marketed to possibly enhance P availability from applied fertilizers

5. Initial P Starter Research Trials in NC
Work by Osmond et al. in 2005, 2006
39 sites at 17 counties for corn; 14 sites at 8 counties for cotton
STP > 100
N-only starter vs. N+P starter (20-30 lbs N and/or P2O5 per ac)

6. Corn Yields and Soil Test Phosphorus Levels

7. Corn Yields: Coastal Plain

8. Is Starter P Necessary on Very High STP Soils?
Data from 2005 & 2006 should have shown differences due to the cool, wet spring
Across all locations, no difference

9. Theory behind AVAIL: Promotional Claims
Negatively charged organic co-polymer
NOT a slow release product or nutritional product
Maleic and itaconic acids
Increases negative charge around fertilizer, essentially attempts to increase CEC
Reduces formation of
insoluble P – Al, Ca,
Fe complexes
Enough to make a difference?

10. Properties of Maleic and Itaconic Acids
Maleic Acid
Organic compound
Two carboxyl groups
Soluble in water
Similar to organic acids that are pumped out of roots
Itaconic Acid
Organic compound
Formed from the distillation of citric acid
Used in plastics
There is no published information on the mode of action for Maleic-Itaconic copolymer in soil or in agricultural applications

11. Phosphorus Fertilizer Trials: 2007-2009
Two studies with different design, each evaluating similar response variables.
Objectives
Determine whether starter P fertilizer is useful on soils with STP of medium, high, or very high (PI>25)
Evaluate the use of starter P fertilizer, with and without Avail fertilizer enhancer, on early season plant color and height, plant nutrient uptake, stover/silage yield, and grain yield.

12. Soil Interpretation Indexes
Response
0-10
Very Low
High
11-25
Low
26-50
Medium
Medium/Low
51-100
None/Low
100+
Very High
None
PI * 1.2 = ppm M-3 P
PI * 2.1 ~ lb P/ac to 8”

13. Experiment One: 2007 & 2008
Medium Soil Test P (25-50 PI), High Soil Test P ( PI), and Very High Soil Test P (> 100)
Locations: Waynesville (CT), Salisbury (NT), and Fletcher (CT)
Treatments
Starter 30 lb N ac-1
Starter 30 lb N ac-1 and 30 lb P205 ac-1
Starter 30 lb N ac-1 and 30 lb P205 ac-1 + Avail
N source: ; P source:
N added to all treatments at V6 for a total of 200 lb N ac-1
P applied in 4” band over the row
RCBD, 4 Replications
How was N applied?

14. Experiment One: 2007 & 2008 4-row plots, 25’ or 30’ long
Plant height determined ~3 weeks after emergence
Relative color also determined, scaled 0 (dark green) to 3 (yellow or purple)
Corn grain yield from center 2 rows of each plot (20’ total), corrected to 15.5% moisture
Tissue and grain samples at harvest for N and P analysis
How was N applied?

15. Corn Yield 2007 & 2008: Fletcher High Soil Test Phosphorus

16. Corn Yield 2007 & 2008: Salisbury High Soil Test Phosphorus

17. Corn Yield 2007 & 2008: Waynesville High Soil Test Phosphorus

18. Corn Yield 2008: Waynesville Medium Soil Test Phosphorus
One year only

19. Corn Yield 2007 & 2008: Salisbury Medium Soil Test Phosphorus

20. Corn Yield 2008: Fletcher Low Soil Test Phosphorus

21. Trial 1 Conclusions: Starter Phosphorus Fertilizer
Yields similar across STP levels
No treatment affect on grain or silage yield
No treatment affect on grain N or P
For mineral soils, starter phosphorus fertilizer is not necessary for corn when soil test P is high or very high
For piedmont and mountain soils, starter phosphorus fertilizer may not be necessary for corn when soil test P is medium
No advantage to Avail fertilizer enhancer on any measured variables

22. Experiment Two: 2008 & 2009 P Rate Trial
Medium Soil Test P (25-50 PI)
Location: Fletcher
P recommendation: 70 lb P205 ac-1
Starter Fertilizers
39 lb N ac-1 N
39 lb N ac-1 N + 25, 50, 75, 100, 125 lb P205 ac-1
39 lb N ac-1 N + Avail + 25, 50, 75, 100, 125 lb P205 ac-1
Starter surface banded 2” to side of seed furrow
N source: 30%UAN; P source:
N added to all treatments at V6 for a total of 230 lb N ac-1

23. Experiment Two: 2008 & 2009 P Rate Trial
RCBD, 4 or 5 replications
4-row plots, 30’ long
Plant height determined ~3 weeks after emergence
Relative color also determined, scaled 0 (dark green) to 3 (yellow or purple)
Corn grain yield from center 2 rows of each plot (20’ total), corrected to 15.5% moisture
Tissue and grain samples at harvest for N and P analysis
How was N applied?

24. Plant Color at V6 Rating Color Dark green 1 Green 2 Light green 3
Dark green 1
Green 2
Light green 3
Yellow/purple

25. Plant Height at V6

26. Corn Grain Yields: 2008 and 2009 This is pooled data-both years
25 lb best, avg stp 40
12000 = 192 bu/ac
13000 = 208 bu/ac

27. Corn Stover: and 2009
25 lb best, avg stp 40

28. Stover P Uptake

29. Trial 2 Conclusions: Starter Phosphorus Rate and Avail
No treatment affect on grain yield or stover
No treatment affect on grain or stover N or P
Early season differences in color and height (2009) did not translate into yield differences
For CT mountain soils
Starter P fertilizer may not be necessary for corn when soil test P is medium
No advantage to Avail fertilizer enhancer, regardless of rate, on any measured variables

30. Take Home Message
Starter P not likely to result in positive yield response for corn grown in mineral soils with STP medium or above
Avail fertilizer enhancer did not improve yields or P uptake by corn on medium STP soils

31. Acknowledgements Wesley Childres, Soil Science
Randy Weisz, Crop Science
Ron Heiniger, Crop Science
Dan Israel, Soil Science
Agrium
Corn Growers Association of North Carolina
North Carolina Small Grain Growers Association
NCDENR – USEPA 319 funds
Southern States
Yara

32. Participants in Starter P Study
Mike Carroll – Craven
Josh Gady - Duplin
Keith Wood - Cherokee
Art Bradley – Edgecombe
Louie Johnson – Greene
Mark Keene – Lenoir
Josh Beam – Lincoln
Bryant Spivey – Onslow
Ben Knox – Union
Kevin Johnson – Wayne
Norman Harrell - Wilson
Producers who helped!
Sheri Cahill – NCSU, Soils
Amy Johnson – U. Tenn
David Hardy – NCDA&CS
Gaylon Ambrose – Beaufort/Hyde
Anthony Cole – Buncombe, Alleghany, Rowan, Henderson
Seth Nagy/Lynn Howard – Caldwell
Mark Powell – Camden
C. Mike Williams – Chowan
Al Wood – Pasquotank
Many field agents across North Carolina helped with these trials, as did some NCDA&CS staff. We greatly appreciate those farmers who worked with us.

33. Thank You Questions?

34. Maleic and Itaconic Acid: Skeletal Frame

35. Phosphorous in an acidic soil environment
Soil system has significant Fe and Al oxides
CEC occupied by Fe and Al

36. Phosphorous in an acidic soil environment
Formation of insoluble Fe and Al Phosphates
P no longer readily available to plants

37. Phosphorous in an acidic soil environment
Formation of insoluble Fe and Al Phosphates
P no longer readily available to plants

38. Concept of P Fertilizer treated with AVAIL
AVAIL adds negative charge around the P molecules

39. Concept of P Fertilizer treated with AVAIL
Soil cations attracted to the negative charges, allowing P molecules to remain plant available

40. Current specialty crop fertility projects

41. Fundamental Issues
Fertilizer cost, limited product availability at local level
Consequently, many growers have reduced or eliminated fertilizer inputs….impact on longer term effects???
Growers looking for alternatives - renewed industry push of ‘specialty’ fertilizers and products
“Green” movement: public perception and environmental issues at the forefront
Buy local! Produce quality vs. quantity

42. Conclusions: Starter Phosphorus Fertilizer
For mineral soils, starter phosphorus fertilizer is not necessary for corn when soil test P is high or very high
For piedmont and mountain soils, starter phosphorus fertilizer may not be necessary for corn when soil test P is medium
Starter phosphorus still needed for organic or mineral organic soils for low, medium and high soil test P

43. Corn Grain Yields: Fletcher
This is pooled data-both years
25 lb best, avg stp 40
12000 = 192 bu/ac
13000 = 208 bu/ac

44. Corn Yields Grain: Fletcher
This is 2008 data
25 lb best, avg stp 40

45. Plant Height at V6