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Phosphorus Nutrition Of Corn

Phosphorus Nutrition Of Corn. 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

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Phosphorus Nutrition Of Corn

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  1. Phosphorus NutritionOf 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. Corn Root System Development 36 Days 8 Weeks Mature Source: Weaver, 1926

  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. Mycorrhizae • “Fungus-root” • Extend to absorb P from more soil • Decline with increasing P fertility, fallow Effect of fertilizer P on corn mycorrhizae. Mean of 2 years, 1997/98, Quebec. Soil test P (Mehlich 3) was 65 to 87 ppm. Adapted from Liu et al., 2002

  6. Early P Nutrition – Outdoor Hydroponics All treatments received high P after V3-V4 (ISU) Mean of 2 years, 1985-1986 Source: Barry & Miller, 1989

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

  8. 75% 90 Silking 80 70 60 50 Total P2O5 uptake, lb/A Maturity Maximum uptake rate 40 2 lb/A/day @ 45 dap 30 20 10 0 0 15 30 45 60 75 90 105 120 135 Days after planting Nutrient Uptake in Corn Versus Stage of Growth Corn grown in silt loam at Purdue Agronomy Farm, Indiana. Silt loam soil; planted May 5, 1971; final grain yield 187 bu/A. Source: Mengel & Barber, 1974

  9. Nutrient Uptake: • Total uptake ~0.55 lb P2O5per bushel of grain yield • Silage harvest removes 3.2 - 4.8 lb P2O5 per ton at 65% moisture

  10. Nutrient Removal in Grain: 0.34 - 0.44 lb of P2O5 per bushel Source: Heckman et al., 2001

  11. P Deficiency in Corn Seedlings

  12. Why Broadcast? • 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

  13. Band Application • 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

  14. Placement Options Source: Randall, et al., 2001

  15. Low fertility High fertility Ridge - Placement Fall chisel Fall chisel Ridge - till till ——— Two - year average, bu/A ——— Control 84 87 156 150 Broadcast 110 102 151 151 Surface band 108 112 152 152 Deep band 118 123 153 153 Fertility Affects Impact of P and K Placement Source: G.W. Rehm, Minnesota

  16. Placing P With the Seed • 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 Source: Bates, 1971; Richards, et al., 1985

  17. Seed Placement: Small Amounts, Liquidor Granular 2 Mean of three Ontario sites 3 Mean of three products: 10-34-0, 6-24-6, 8-19-3 1 Mean of two hybrids at each of two Ontario sites; seed-placed 8-19-3 Source: Lauzon et al., 1995

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

  19. P Sources and Solution pH Symbol Compound Formula pHTSP monocalcium Ca(H2PO4)2 1.5 phosphate MAP monoammonium NH4H2PO4 3.5 phosphate TPP1 triammonium (NH4)3HP2O7 6.0 pyrophosphate DAP diammonium (NH4)2HPO4 8.0 phosphate 1 Main P form in liquid 10-34-0

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

  21. 100 90 80 Iowa 70 Illinois Relative Yield, % Missouri 60 50 40 30 0 5 10 15 20 25 30 35 40 Soil Test P, ppm [Bray P1] Corn Response to P Source: PKMAN Version 1.0, PPI

  22. 50 45 40 35 30 298 lb P2O5 in 1975 25 Bray P-1 (ppm) 20 15 10 5 0 lb P2O5 in 1975 0 1975 1977 1979 1981 1983 1985 1987 1989 Mining P Reduces Soil Test P Data source: Webb et al., 1992 (Iowa)

  23. 298 lb P2O5 in 1975 200 175 150 125 Corn grain yield, bu/A 100 0 lb P2O5 in 1975 75 50 1976 1978 1980 1982 1984 1986 1988 Residual Effect of P Data source: Webb et al., 1992 (Iowa)

  24. Phosphorus and Zinc • 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 * P and Zn band-applied Data source: Adriano and Murphy

  25. Phosphorus and Zinc • Continuous application of very high rates of P does not always induce greater Zn deficiency (Mallarino, 1995) Adapted from Shang & Bates, 1987

  26. Effect of N and P onCorn Yield 200 with P 180 N rate at MEY: with P = 159 lb/A without P = 145 without P 160 140 Yield, bu/A P increased N use efficiency instead of greatly increasing N fertilizer demand 120 100 80 60 0 20 40 60 80 100 120 140 160 180 200 Irrigated continuous corn, Kansas, 30 years data, 1961-1991. N rate, lb/A Source: Schlegel et al., 1996

  27. Effect of N and P onNet Revenue 200 with P 150 The economic optimum N rate with P is 159 lb/A. P increased profit by about $120/A at this rate without P 100 Net revenue, $/A 50 0 0 20 40 60 80 100 120 140 160 180 200 -50 Corn $2.30/bu, N $0.15/lb, P2O5 $0.24/lb; other costs $240/A -100 N rate, lb/A Source: Schlegel et al., 1996, 30 year average

  28. P Reduces Residual Soil Nitrate and Potential for Nitrate Leaching After 30 Years 200 with P without P 150 -N in upper 10 ft, lb/A At optimum N rate, P reduced residual nitrate by 66% 100 3 50 Soil NO 0 0 40 80 120 160 200 N rate, lb/A Source: Schlegel et al., 1996; 30 year average

  29. Phosphorus Hastens Corn Maturity

  30. 250 Drying cost reduction $/A 200 Yield response income /A, 5 O 150 2 100 Net return to 40 lb P 50 0 0 40 80 120 160 200 Fertilizer nitrogen rate, lb/A Phosphorus Hastens Maturity and Lowers Drying Costs, Adding to Return to P Calculated from Dhuyvetter and Schlegel. 1994. Corn, $2.50/bu; N, $0.15/lb; P2O5, $0.24/lb

  31. 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

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

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