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

Average Soil Test Phosphorus 70% medium or above

Soil Test Phosphorus: Corn/Soybean Rotation

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

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)

Corn Yields and Soil Test Phosphorus Levels

Corn Yields: Coastal Plain

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

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?

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

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.

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”

Experiment One: 2007 & 2008 Medium Soil Test P (25-50 PI), High Soil Test P (51-100 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: 34-0-0; P source: 18-46-0 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?

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?

Corn Yield 2007 & 2008: Fletcher High Soil Test Phosphorus

Corn Yield 2007 & 2008: Salisbury High Soil Test Phosphorus

Corn Yield 2007 & 2008: Waynesville High Soil Test Phosphorus

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

Corn Yield 2007 & 2008: Salisbury Medium Soil Test Phosphorus

Corn Yield 2008: Fletcher Low Soil Test Phosphorus

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

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: 18-46-0 N added to all treatments at V6 for a total of 230 lb N ac-1

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?

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

Plant Height at V6

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

Corn Stover: 2008 and 2009 25 lb best, avg stp 40

Stover P Uptake

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

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

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

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.

Thank You. Questions?

Maleic and Itaconic Acid: Skeletal Frame

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

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

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

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

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

Current specialty crop fertility projects

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

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

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

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

Plant Height at V6