Phosphorus Product Properties for 4R Nutrient Stewardship. Tom Bruulsema, Phosphorus Program Director, IPNI

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1 Phosphorus Product Properties for 4R Nutrient Stewardship Tom Bruulsema, Phosphorus Program Director, IPNI

2 The International Plant Nutrition Institute is supported by leading fertilizer manufacturers. Formed in 2007 from the Potash & Phosphate Institute, its mission is to develop and promote science for responsible management of crop nutrition

3 Outline 1. Phosphorus Sustainability Issues 2. 4R Nutrient Stewardship Principles of right source Why right time and right place also matter 3. P Balance Trends P use efficiency Soil test P levels

4 Environmental Impact Eutrophication Hypoxia Harmful Algal Blooms Photo credit: Carrie Vollmer-Sanders, The Nature Conservancy

5 Ancaster, Ontario 26 June 2009 tilled corn SOIL EROSION IS A REAL RISK

6 Northwest of Guelph, Ontario 6 April 2014 no-till DISSOLVED P IN RUNOFF AN INVISIBLE RISK

7 Scientific principles for Right Source 1. Consider rate, time, and place of application 2. Supply nutrients in plant-available form 3. Suit soil physical and chemical properties 4. Recognize synergisms among nutrient elements and sources 5. Recognize blend compatibility 6. Recognize benefits and sensitivities to associated elements

8 Research shows potential for altered P placement needs in high density high yield maize Banding P fertilizer cm deep Yield, t/ha Dr. F.E. Below, University of Illinois none 15cm beside under

9 Fertilizer P is Soluble P MAP ( ) has water solubility of 370 g/l = 84 grams P per litre = 84,000 mg P per litre Maumee river target for DRP = mg P per litre Targets for Lake Erie: Western Basin mg/l Central Basin mg/l Eastern Basin mg/l

10 Phosphorus Adsorption Oxygen Hydrogen Phosphorus Diffusion Ligand Exchange Clay, Carbonate, Oxide Surfaces

11 Solubility 3 to 4 molar Pathway of P fertilizer in temperate soils Granule wetting: capillary flow of H 2 O into granule bringing Al, Fe, Ca along; diffusion of P out of granule Time needed in incubations Most P leaves granule within days MAP ( ) NH 4 H 2 PO 4 NH 4 P minerals Dicalcium phosphate dihydrate (DCPD) Mineral residues can be left behind like crandallite (a Ca-Al- OH phosphate) for months 5 weeks Moderately acid soils Fe, Al, Ca P minerals (strengite, vivianite, variscite, apatite analogs) Alkaline soils Ca P minerals (octacalcium phosphate, apatite analogs) 10-5 to 10-6 molar ( mg L -1 ) 6 months or longer P sorbed by hydrous oxides of Fe & Al, apatite analogs Based on solubility and spectroscopic evidence P sorbed by CaCO 3 or Fe oxides replacing H 2 O & OH, apatite analogs

12 Dissolved P, ppm Rotational tillage & dissolved P Waterloo, IN before fertilizer application Time (minutes) 15-year no-till sites, corn-soybean rotation. Tillage 12 April with finisher chisel plow to 6 depth. Residue cover 57% for NT and 20% for RT. Rainfall applied 22 June to 2 July. Smith et al Soil & Tillage Research 95: Rainfall intensity, inches/hour Runoff volume higher in NT than in RT: 61 vs 39 mm

13 Rotational tillage & dissolved P Waterloo, IN Dissolved P, ppm one day after fertilizer surface 100 lb/a P 2 O Rainfall intensity, inches/hour P 2 O 5 loss 7.3 lb/a 2.5 lb/a Time (minutes) 15-year no-till site, corn-soybean rotation. Tillage 12 April with finisher chisel plow to 6 depth. Residue cover 57% for NT and 20% for RT. Rainfall applied 22 June to 2 July. Smith et al Soil & Tillage Research 95:11 18

14 Effect of tillage on preferential flow and phosphorus transport Soil type: Silt loam Tile depth: 36 Soil test P: 30 ppm Mehlich-3P Tillage: No-till TD management May 6 th Applied 180 lb/a May 8 th Tilled field TD1 (disc) (TD2 remained no-till) Study Objective Compare P transport before and after tillage and between tilled and no-till fields TD meters Drainage area Tile outlet Rain gauge Ohio, USA UBWC Williams and King, USDA-ARS, Columbus, Ohio Water Resources Research 52:

15 Broadcast variable rate application on May 6, 2014 Williams and King, USDA-ARS, Columbus, Ohio

16 DRP (g/ha) Discharge (mm) DRP (mg/l) Before P application & tillage (April 28 th ) TD1 Discharge Preferential flow DRP TD After P application & tillage (May 12th) P incorporated P not incorporated TD TD Discharge DRP Incorporating P reduced DRP loss by 85% Williams and King, USDA-ARS, Columbus, Ohio Water Resources Research 52:

17 Understanding of agricultural P loss Old New Focused on total P Soil erosion is the greatest loss Reduce P loss by soil erosion with conservation tillage Source rate time place unimportant in comparison to erosion (except when soil test P excessive) Dissolved P more available to algae than particulate Conservation tillage increases loss of dissolved while decreasing particulate Source rate time place AND tillage all important

18 Ohio Ag Retailer survey Lake Erie basin March 2013 a lot of P is applied without incorporation! Soil testing: >80% Grid (2.5 A) 25% Soil type 11% Management zone 6% Variable Rate Application 33% Placement: Planter band 30% Strip-till band 4% Incorporation <7 d 15% Broadcast NT or >7d 51% Timing: Fall 41% Spring 41% Greg LaBarge and Steve Prochaska, Ohio State University Extension, 2014.

19 Lower solubility fertilizer right source? Struvite, brushite, etc. Water solubility 3 orders of magnitude lower than MAP and DAP (0.2 g/l versus 370 to 580 g/l) But still considerably higher than critical P concentration for plants & algae (25 versus 0.2 & 0.03 mg/l) Efficacy as fertilizer Plant recovery of P equal to that of MAP in greenhouse pot studies (Katanda et al., 2016) Runoff comparisons not available

20 Phosphorus Balance Trends Crop removal of P increasing with yield P input exceeded crop removal in the past In 2010, surplus increasing in Asia but gone in high income countries High income countries China and India Bouwman et al., Nature Scientific Reports 7:40366 DOI: /srep40366

21 Soil test P determines right rate and source

22 Strip tillage with granular placement puts P in the right place and controls erosion.

23 Summary 1. Among phosphorus sustainability issues, eutrophication is the most urgent. 2. 4R Nutrient Stewardship addresses sustainability issues including eutrophication. 3. Runoff risks can be managed by placement or timing. 4. The wide range in soil test levels suggests need for a range of phosphorus products for building soil fertility, replenishing crop removal, or enabling drawdown.