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Phosphorus Nutrition of Soybean

Phosphorus Nutrition of Soybean. Outline – P Nutrition of Soybean. P uptake by above-ground plant tissue Soybean root morphology P influx by roots Yields and soil test P levels P placement P timing P and soybean pests/diseases. Examining uptake throughout the season.

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Phosphorus Nutrition of Soybean

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  1. Phosphorus Nutrition of Soybean

  2. Outline –P Nutrition of Soybean • P uptake by above-ground plant tissue • Soybean root morphology • P influx by roots • Yields and soil test P levels • P placement • P timing • P and soybean pests/diseases

  3. Examining uptake throughout the season P Uptake by Above-Ground Plant Tissue

  4. 450 400 N P2O5 K2O 350 300 250 Aerial accumulation (lb/acre) 200 150 100 50 0 0 20 40 60 80 100 120 140 160 Days after planting Nutrient Uptake by 80 bu/A Soybeans Source: Henderson and Kamprath, 1970

  5. Soybean P Uptake 100 90 80 Total P uptake:12 – 24 lb P2O5/A Beans 70 60 Pods 50 % of total uptake Petioles Stems 40 30 20 Petioles (fallen) Leaves Leaves(fallen) 10 0 Days after emergence 0 28 56 84 112 V1 V6 V10 R4 R6 R7 Growth stage (inferred) Source: Hanway and Weber, 1971

  6. Soybean Phosphorus Derivedfrom Fertilizer Source: Ham and Caldwell, 1978

  7. Soybean Phosphorus Content Derived from Fertilizer Soil P level 60 Low 50 40 Medium 30 % of P derived from fertilizer High 20 10 0 20 40 60 80 100 120 Days after planting Source: Bureau et al., 1953

  8. Establishing a background for discussions of P placement Soybean Root Morphology

  9. Soybean Root Growth 6 in. • Phase 1(1st month after planting) • Rapid vegetative top growth • Downward taproot growth • Development of horizontal laterals in upper soil profile Source: Mitchell and Russell, 1971

  10. Soybean Root Growth • Phase 2(2 – 2.5 months after planting) • High rates of top growth(from flowering through pod formation) • More laterals develop in upper soil profile • Some laterals begin to turn downward 6 in. Source: Mitchell and Russell, 1971; Raper and Barber, 1970

  11. Soybean Root Morphology • Left side:single soybean plant grown in isolated plot • Primary lateral roots branch from taproot within upper 15 cm (6 in.) • Below 15 cm (depth of cultivation), taproot degenerated to a root with a diameter similar to primary laterals but with less branching (approx. 10 wk. after planting) Source: Raper and Barber, 1970

  12. Soybean Root Morphology • Right side:soybean grown in 30 in. rows • Primary lateral roots branch from taproot within upper 15 cm (6 in.) • Near center of rows (45 cm or 18 in.), laterals angle down sharply as they encounter root zone of neighboring plant (approx. 10 wk. after planting) Source: Raper and Barber, 1970

  13. Soybean Root Growth • Phase 3(Seed set to maturity) • Continued rapid rates of downward extension of laterals • Laterals penetrated deeper than the tap root Source: Mitchell and Russell, 1971

  14. Roots Proliferate in Zones of Higher P Concentration 0.8 Soybean 0.7 Corn 0.6 1:1 0.5 Portion of total root lengthin P-treated volume 0.4 0.3 0.2 0.1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 P treated soil portion, % Source: Borkert and Barber, 1985

  15. Effects of P or Mycorrhizae on Soybean Shoot Dry Weight Greenhouse study Non- mycorrhizal DM Mycorrhizal DM 3.0 100 Non-mycorrhizal infection Mycorrhizal infection 2.5 80 2.0 60 Shoot dry weight, grams % of root colonized 1.5 40 1.0 20 0.5 Initial Bray 1 soil test P = 8 ppm 0 0 0 115 345 920 Applied P rate, lb P2O5/A Source: Lambert et al. 1979

  16. Cultivar choice Root angle Root elongation rate Planting date Soil temperature Soil moisture Photoperiod Quantity of radiation Tillage Soil moisture Soil temperature Soil bulk density Soil aeration Soil fertility Plant dry matter distribution Root proliferation Irrigation Soil moisture profile Management Factors Affecting Soybean Root Morphology Source: Coale and Grove, 1986

  17. Examining how quickly roots can absorb P P Influx by Roots

  18. Nutrient Influx by Roots • Ions are not simply absorbed according to their ratios in solution • Ions with this characteristic influx pattern require energy to be absorbed • H2PO4-, HPO42- • K+ • Maximum influx is reached at higher solution concentrations (Imax) 22-23 day old soybean roots 3.0 Imax 2.5 2.0 1.5 Influx, 10-14 lb P2O5 / (in2 s) 1.0 0.5 0.0 0 1 2 3 4 5 -0.5 Solution P, 10-6 lb P2O5/gal Sources: Barber, 1984; Edwards and Barber, 1976

  19. Nutrient Influx Depends on Both P and K Fertility Low P limits P diffusionand energy for P uptake Low P limits energyfor K uptake P2O5 influx by soybean roots K2O influx by soybean roots 10.0 55 ppm Bray P-1 9.0 8.0 7.0 55 ppm Bray P-1 6.0 Influx, 10-13 lb / (in2 s) 5.0 4.0 3.0 11 ppm Bray P-1 11 ppm Bray P-1 2.0 1.0 0.0 50 70 90 110 130 150 50 70 90 110 130 150 Soil test K, ppm Source: Hallmark and Barber, 1984

  20. Corn P Influx Varies withPlant Age 5 4 3 Influx, 10-5 lb P2O5 / (in. day) 2 1 Soybean 0 0 20 40 60 80 100 120 -1 Plant age, days Sources: Barber, 1978; Mengel and Barber, 1974

  21. Examining how productionlevel is related to soil testP level Yields and Soil Test P Levels

  22. 100 80 60 Relative grain yield, % 40 Corn Soybean 20 0 0 0 10 10 20 20 30 30 40 40 50 50 60 60 70 70 80 80 Soil test Bray P-1, ppm Soil Test P Calibration Data Source: Mallarino, 1999

  23. MO IL AR KY MS AL Comparisons of Soil Test P Calibration Data 120 100 80 60 Relative yield, % 40 20 0 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 Bray P-1 soil test level, ppm Source: Snyder, 2000

  24. Broadcast and bandedapplications P placement

  25. Nutrient Placement Considerations Conceptual model(nutrient deficient soil) • Banding: • Less soil volume fertilized • Smaller portion of fertilizer is “tied up” • Roots proliferate where N and P are found • Rate may be too low to maximize yield • Fewer roots exposed to supply • Increase in influx rate by roots may not compensate for fewer total number of roots near P supplies High nutrient rate Dry matter yield Low nutrient rate 0 20 40 60 80 100 Fertilized soil fraction, % Source: Anghinoni and Barber, 1980

  26. Starter vs. Broadcast:Irrigated Zone • 3 of 10site-years responded significantly • pH: 7.6 – 8.1 • Olsen P: 5.6 – 10.7 ppm • Calcareous soil • Band placement:2 in. below2 In. to the side (2x2) Range in average yields:50 - 71 bu/A 25 20 Broadcast 15 2x2 Band 10 Soybean yield response, % 5 0 0 20 40 60 80 100 -5 P2O5 rate, lb/A Source: Rehm, 1986

  27. Starter vs. Broadcast:Dryland Zone 60 50 1 in. below 40 1 in. x 1 in. 30 Yield response, % With seed 20 Spring broadcast 10 Fall broadcast 0 0 25 50 75 100 125 -10 P rate, lb P2O5/A Source: Bullen et al., 1983

  28. Starter vs. broadcast:Temperate Rain Fed Zone • 20 site-years at research stations • 4 – 29 ppmBray P-1 • 9 sites tested Very Low to Low(6 to 15 ppm Bray P-1) • 7 of the 9 sites (78%)(6 to 11 ppm Bray P-1) showed significant responses to P • P placement did not influence soybean yield Averaged overresponsive sites 13.1 14 11.6 12 Averaged overall sites 10 8 Yield response, % 6 3.9 3.9 4 2 0 Starter Starter Broadcast Broadcast Source: Borges and Mallarino, 2000

  29. Comparison of Placement Combinations and Rates 19.9 19.6 20 Bray P-1: 3.5 ppmNH4OAc K: 150 ppm 14.0 15 Yield response, % 10 7.2 broadcast + w/seed 5.0 broadcast + band 5 broadcast w/seed band 0 N: 4 10 0 4 10 P2O5: 18 46 60 78 106 K2O: 5 12 30 35 42 Source: Ham et al., 1973

  30. Deep Banding vs. Broadcast • 20 site-years at research stations • No-till systems • 0 – 6 in. soil samples: • 4 – 29 ppm Bray P1 • pH 5.9 – 7.1 • Significant responses to P occurred on 7 sites ranging from 6 – 11 ppm Bray P1 • Average response at these sites:4.6 bu/A • 5 of the 7 sites showed no differences in placement Range in average yields:26 – 63 bu/A 30 in. 6 - 8 in. 30 in. Source: Borges and Mallarino, 2000

  31. Deep Banding vs. Broadcast • 11 site-years on farmer fields • No-till systems • 0 – 6 in. soil samples: • 5 – 34 ppm Bray P1 • pH 5.8 – 7.5 • Across all site-years, there was a slight(1 bu/A) advantage to P fertilization, and no difference between placement methods Range in average yields:37 – 58 bu/A 7.5 in. 6 - 8 in. 30 in. Source: Borges and Mallarino, 2000

  32. Considerations forPlacement • Banding is expected to be superior when soil test levels are low and only smaller rates of P are applied • Broadcast applications may be superior to banded applications when rainfall or irrigation keeps moisture in the upper part of the soil profile • Placement of bands directly below the seed may be better than other band placements • Band and broadcast applications used together may be better than either one applied on its own

  33. Comparing fresh andresidual effects of fertilization P Timing

  34. Annual vs. Biennial:Broadcast Applications Range in average yields:24 – 48 bu/A • Corn/soybean rotation • Long no-till history • P timing (0-46-0) • Every 2-yr.80 lb P2O5/A • Every yr.40 lb P2O5/A • 2 of 4 site-years showedno timing differences • 1 site (18 ppm Bray P1):annual > biennial by 3 bu/A • 1 site (37 ppm Bray P1): biennial > annual by 3 bu/A 30 in. Source: Buah et al., 2000

  35. Annual vs. Biennial:Broadcast Applications • Corn/soybean rotation • Long no-till history • P timing • Every 2 yr.(0, 30, 80, 160 lb P2O5/A) • Every yr. (0, 15, 40, 80 lb P2O5/A) • Direct > residual 2 out of 3 years • 2 bu/A average response • Bray P-1: 6 – 14 ppm Range in average yields:37 – 46 bu/A 10 in. Source: Buah et al., 2000

  36. Annual vs. Biennial:Starter Applications • Corn/soybean rotation • Long no-till history • P timing (0-46-0) • Every 2-yr.80 lb P2O5/A • Every yr.40 lb P2O5/A • 2 of 4 site-years showedno timing differences • 1 site (18 ppm Bray P1):annual > biennialby 6 % • 1 site (37 ppm Bray P1): biennial > annual by13 % Range in average yields:24 – 48 bu/A 30 in. 3 - 4 in. 2 in. 30 in. Source: Buah et al., 2000

  37. Annual vs. Biennial:Starter Applications • Corn/soybean rotation • Long no-till history • P timing • Every 2 yr.(0, 30, 80, 160 lb P2O5/A) • Every yr.(0, 15, 40, 80 lb P2O5/A) • Annual > biennial 2 out of 3 years • 2 bu/A average response • Bray P-1: 6 – 14 ppm Range in average yields:37 – 46 bu/A 10 in. 4 in. 30 in. Source: Buah et al., 2000

  38. Residual effect of a single, large application of P 0 lb P2O5 applied initially67.5 lb P2O5/A applied annually 120 110 100 90 % of yield attained with 600 lb P2O5/A applied initially, and 67.5 lb P2O5/A applied annually 80 600 lb P2O5 applied initially 0 lb P2O5/A applied annually 70 60 50 40 1975 1980 1985 1990 1995 2000 Year Source: Dodd and Mallarino, 2005

  39. Timing Considerations • Cases where annual applications may be better than biennial applications in no-till systems: • Soils with lower soil test levels • Soybeans planted in narrower rows • Other tillage systems need to be investigated • Single, larger applications of P can have significant residual value • Builds soil test levels • Can be performed when economics of larger applications are favorable • Allows P to be omitted in times of unfavorable economic conditions

  40. Phosphorus and soybean pests/diseases

  41. Nutrition and Foliar Diseases:Asian Rust Source: Piccio and Fanje, 1980

  42. Nutrition and Diseases:Soybean mosaic virus 50 K2O 45 40 35 30 P2O5 SMV incidence, % 25 N 20 15 Total N + P2O5 +K2O,at equal rates 10 5 0 0 25 50 75 100 125 150 Nutrient rate, lb/A Source: Pacumbaba et al., 1997

  43. Nutrition and Nematodes:Soybean cyst nematode (SCN) Cultivar highly susceptibleto SCN races 3 and 4 18 30 16 25 14 Yield response 12 20 10 Cysts / 100cc 15 Yield response, % 8 6 10 4 5 2 0 0 0-0 30-30 60-60 90-90 120-120 Fertilizer mixture (P2O5 - K2O), lb/A C/C S/S C/S Yield response Source: Howard et al., 1998

  44. Nutrition and Nematodes:Soybean cyst nematode (SCN) Cultivar resistantto SCN races 3 and 4 18 30 16 25 14 12 20 Yield response 10 Yield response, % Cysts / 100cc 15 8 6 10 4 5 2 0 0 0-0 30-30 60-60 90-90 120-120 Fertilizer mixture (P2O5 - K2O), lb/A C/C S/S C/S Yield response Source: Howard et al., 1998

  45. Conclusions • At harvest, most of the P in the above-ground portion of soybean is in the grain • At lower soil test levels, more of the P taken up by the plant comes from applied P • In the first month after planting, root development is primarily characterized by elongation of the taproot • In subsequent months, soybean develops much of its root system near the soil surface • Compared to corn, the rate of P influx by soybean roots is about 4 times slower in the first 20 days • P proliferates soybean roots when present in concentrated zones • Mycorrhizae can increase soybean growth at low soil test P levels, even when P is applied

  46. Conclusions • Soil test calibration data provide a biological evaluation of chemical tests • Average calibration relationships can be similar across large geographies • Placement of bands directly below the seed may be better than other band placements • Band and broadcast applications used together may be better than either one applied on its own • Annual applications appear to be superior to biennial applications when plant spacing is narrower and soil tests are low • P can help reduce the incidence and or severity of some soybean diseases

  47. 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

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