1. Phosphorus Nutrition Of Corn

2. Outline – P Nutrition of Corn Changes in root system development over the season Impacts on attainable yield potential Requirements through growth stages Placement options Soil test levels and corn response to P inputs Profitability of P fertility management

3. 36 Days 8 Weeks Mature Source: Weaver, 1926 Corn Root System Development

4. The first roots grow from the seed, but the main root system starts from the first node above the seed. Planting depth affects the depth of the seed roots, but the depth of the initiation of the main root system is the same, regardless of planting depth.

5. Fertilizer P 2 O 5 Rate, lb/A Roots colonized at 6-leaf stage Corn dry matter at silking, tons/A 021%4.5 5519%5.0 11015%5.2 Mean of 2 years, 1997/98, Quebec. Soil test P (Mehlich 3) was 65 to 87 ppm. Adapted from Liu et al., 2002 Effect of fertilizer P on corn mycorrhizae. Mycorrhizae “Fungus-root” Extend to absorb P from more soil Decline with increasing P fertility, fallow

6. P supplied Shoot P @ V1 Shoot P @ V3-V4Kernel,Yield, up to V3-V4%#/plantbu/A High0.580.72444155 Medium0.520.44410138 Low0.490.28398134 All treatments received high P after V3-V4 (ISU) Mean of 2 years, 1985-1986 Source: Barry & Miller, 1989 Early P Nutrition – Outdoor Hydroponics

7. High-yield corn (307 bu/A) Source: Karlen et al., 1988. How a Corn Plant Takes Up Phosphorus

8. Source: Mengel & Barber, 1974 Corn grown in silt loam at Purdue Agronomy Farm, Indiana. Silt loam soil; planted May 5, 1971; final grain yield 187 bu/A. Nutrient Uptake in Corn Versus Stage of Growth 0 10 20 30 40 50 60 70 80 90 0153045607590105120135 Days after planting Total P 2 O 5 uptake, lb/A 75% Silking Maximum uptake rate 2 lb/A/day @ 45 dap Maturity

9. Nutrient Uptake: Total uptake ~0.55 lb P 2 O 5 per bushel of grain yield Silage harvest removes 3.2 - 4.8 lb P 2 O 5 per ton at 65% moisture

10. Source: Heckman et al., 2001 0.34 - 0.44 lb of P 2 O 5 per bushel Nutrient Removal in Grain:

12. P Deficiency in Corn Seedlings

14. Can apply large amounts conveniently Ideal for building soil fertility Minimizes risk of fertilizer injury On fields of low fertility, banded starter P may not be adequate for maximum yield Combinations of broadcast and band applications produce the highest yields on low testing soils Why Broadcast?

15. Overwhelms soil fixation capacity Places nutrients near the seedling –Roots intercept early and proliferate near the band –Including ammonium-N, slows P fixation and lowers pH near the root to improve both P and micronutrient availability Favors the crop over the weeds Keeps nutrients away from the surface –Reduces runoff P concentrations Band Application

16. PP 2 O 5 applied,Grain yield, bu/A applicationlb/A1997-2000 average TillagemethodHigh P siteLow P siteHigh P siteLow P site One-passNone00168104 Starter4050171153 Broadcast80100174164 Fall band4050164144 Strip-tillNone00164103 Starter4050169151 Fall Band4050167143 Source: Randall, et al., 2001 Placement Options

17. Source: G.W. Rehm, Minnesota Fertility Affects Impact of P and K Placement

18. Source: Bates, 1971; Richards, et al., 1985 Ontario research from 1960s and 1970s (52 site-years) showed that 6-24-6 @ 50 lb/A with the seed: –Increased yield by zero to 2.9% –Delayed and sometimes reduced emergence –Hastened time to silking –Decreased grain moisture at harvest Placing P With the Seed

19. P 2 O 5 rate,Corn yield, 1 lb/Abu/A 0137 5151 10146 21148 1 Mean of two hybrids at each of two Ontario sites; seed-placed 8-19-3 2 Mean of three Ontario sites 3 Mean of three products: 10-34-0, 6-24-6, 8-19-3 Corn yield, 2 bu/A Rate, lb P 2 O 5 /A Liquid 3 Granular MAP, 13-52-0 0145 10156 21152157 Source: Lauzon et al., 1995 Seed Placement: Small Amounts, Liquid or Granular

20. Source: Bundy, 2001 Late Planting of Full Season Corn Increased Response to Starter in Wisconsin

21. SymbolCompoundFormulapH TSPmonocalciumCa(H 2 PO 4 ) 2 1.5 phosphate MAPmonoammonium NH 4 H 2 PO 4 3.5 phosphate TPP 1 triammonium(NH 4 ) 3 HP 2 O 7 6.0 pyrophosphate DAPdiammonium (NH 4 ) 2 HPO 4 8.0 phosphate 1 Main P form in liquid 10-34-0 P Sources and Solution pH

22. Soil test Probability of response to P category MN-SD-NDON Very low > 80% Low 60-80%75% Medium 40-60%55% High 20-40%25% Very high < 20%< 25% Category definitions vary among laboratories Soil Test Interpretation: Index of the Likelihood of Crop Response

23. Source: PKMAN Version 1.0, PPI Corn Response to P

24. Data source: Webb et al., 1992 (Iowa) Mining P Reduces Soil Test P 298 lb P 2 O 5 in 1975 0 lb P 2 O 5 in 1975 0 5 10 15 20 25 30 35 40 45 50 19751977197919811983198519871989 Bray P-1 (ppm)

25. Data source: Webb et al., 1992 (Iowa) Residual Effect of P 298 lb P 2 O 5 in 1975 0 lb P 2 O 5 in 1975 50 75 100 125 150 175 200 1976197819801982198419861988 Corn grain yield, bu/A

26. Zn deficiency impairs plant P regulation Either high soil P or large amounts of applied P can induce Zn deficiency if soil Zn is low and no Zn fertilizer is applied P2O5P2O5 ZnYieldLeaf tissue lb/A *bu/AP, %Zn, ppm 001010.1412 0101020.1624 800730.7310 80101620.4117 Data source: Adriano and Murphy * P and Zn band-applied Phosphorus and Zinc

27. Continuous application of very high rates of P does not always induce greater Zn deficiency (Mallarino, 1995) Olsen soil test P, ppm Fertilizer P 2 O 5 applied, lb/A Corn seedling Zn, ppm 1018 608 11521 91518 Adapted from Shang & Bates, 1987 Phosphorus and Zinc

28. Irrigated continuous corn, Kansas, 30 years data, 1961-1991. N rate at MEY: with P = 159 lb/A without P = 145 P increased N use efficiency instead of greatly increasing N fertilizer demand Source: Schlegel et al., 1996 Effect of N and P on Corn Yield 60 80 100 120 140 160 180 200 020406080100120140160180200 N rate, lb/A Yield, bu/A with P without P

29. Source: Schlegel et al., 1996, 30 year average Corn $2.30/bu, N $0.15/lb, P 2 O 5 $0.24/lb; other costs $240/A The economic optimum N rate with P is 159 lb/A. P increased profit by about $120/A at this rate Effect of N and P on Net Revenue -100 -50 0 50 100 150 200 020406080100120140160180200 N rate, lb/A Net revenue, $/A with P without P

30. Source: Schlegel et al., 1996; 30 year average At optimum N rate, P reduced residual nitrate by 66% P Reduces Residual Soil Nitrate and Potential for Nitrate Leaching After 30 Years 0 50 100 150 200 04080120160200 N rate, lb/A Soil NO 3 -N in upper 10 ft, lb/A with P without P

31. Phosphorus Hastens Corn Maturity

32. Corn, $2.50/bu; N, $0.15/lb; P 2 O 5, $0.24/lb Calculated from Dhuyvetter and Schlegel. 1994. Phosphorus Hastens Maturity and Lowers Drying Costs, Adding to Return to P 0 50 100 150 200 250 04080120160200 Fertilizer nitrogen rate, lb/A Net return to 40 lb P 2 O 5 /A, $/A Drying cost reduction Yield response income

33. Summary - P Nutrition of Corn Roots must grow to where the P is, since P is nearly immobile in most soils Seedlings provided with high P develop higher attainable yield potential Uptake of P continues through the season Placement near the seedling often boosts yield. Corn response to P depends on soil test level P fertility management is key to profitability and efficient use of N

34. International Plant Nutrition Institute (IPNI) 655 Engineering Drive, Suite 110 Norcross, GA 30092-2604 Phone: 770-447-0335; Fax: 770-448-0439 www.ipni.net Reference 06128