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This is a PDF version of a power point presentation developed for my soil fertility class. Email if you would like to receive a copy of the powerpoint -

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  • If you are a farmer who found this presentation to be informative, please consider sharing answers to all or some of the questions on slide 50. You can post your answers anonymously here as a comment or you can email them to me -

    Questions on slide 50
    Age? Education? Location? Type and scale of agricultural enterprises?

    What is your typical N program for corn following corn?

    What is your typical N program for corn following soybeans?

    What is your typical N program for corn following other crops?

    If you vary these programs with respect to factors such as soil type, expected yield, price of inputs... please explain

    If consultants or industry agronomists play a role in your N management decisions, please briefly describe.

    Are you familiar with the new N rate calculator on the IA State website? If so, how did you become aware of it and have you spent any time using it?

    Have you read or looked at the N management chapter in the new 24th edition of the IL Agronomy Handbook?

    If you are familiar with the N rate calculator, are you using it as part of your N management decision making?

    Briefly, how has your N management for corn changed during your career?
    Are you sure you want to  Yes  No
    Your message goes here
  • Be the first to like this


  1. 1. NITROGENhas two stable isotopes, 14N and 15N 14N = 99.6% of all NWhy might a researcher decide to use N fertilizer spiked with 15N?
  2. 2. Where is the N on planet earth ?? N Reservoir MegaTons % of Total Biomass 2.8 x 105 0.0002 Water 2.3 x 107 0.014 Atmosphere 3.86 x 109 2.3 Geosphere 1.636 x 1011 97.7 Crust 0.13 - 1.4 x 1010 0.78-8.4 Soils and Sediments 0.35 - 4.0 x 109 0.21-2.4 Mantle and Core 1.6 x 1011 95.6 Most geosphere N is deep within the earth and has little relevance to biological cycles.
  3. 3. Biologically relevant NReservoir/Pool Type MegaTons BR N % of TotalBiomass 2.8 x 105 <0.01 0.0002Water 2.3 x 107 < 1% 0.014Soil 0.35 x 109 ~8% 0.21Atmosphere 3.86 x 109 2.3 % > 90 N2 ~ 78% of the earth’s atmosphere
  4. 4. Why is N2 so unreactive ???N2 is chemically unreactive at the temperatures and pressures of the hydrosphere,biosphere, and atmosphere because of its triple bond. This triple bond can only bebroken under extreme temperatures and or pressures or in the presence of selectenzymes.
  5. 5. Lightning Pollution Reactive (primarily from engines) NReactive Industrial Reactive N fixation N N Biological N fixation in Reactive agricultureBiological Nfixation in nature N
  6. 6. ~ 5 MT NH3 manufacturing plants currently produce ~ as ~ 20 MT much reactive N as all other processes on planet earth ~ 30 MT ~ 85 MT > 130 MT ~ 90% used for fertilizer
  7. 7. Human activities ~ 20 MT are fertilizing the entire planet with reactive N~ 30 MT > 130 MT
  8. 8. Nitrogen has many different oxidation states ! Species Name Oxidation State C-NH2 Organic N Plant NH3, NH4+ Ammonia, ammonium ion -3 Most reducedmetabolism N2H4 Hydrazine -2 more NH2OH Hydroxylamine -1 electrons N2 Nitrogen 0 Poorly drained N2O Nitrous oxide +1 soils NO Nitric oxide +2 less HNO2, NO2- Nitrous acid, nitrite ion +3 electrons Well NO2 Nitrogen dioxide +4 aerated soils HNO3, NO3- Nitric acid, nitrate ion +5 Most oxidized
  9. 9. Do any of you remember this view ???Why is this Ammonium Nitrate is a powerfulcombination nitrate oxidizingexplosive ? + agent! diesel fuel April 19, 1995 - Alfred P. Murrah Federal Building
  10. 10. The on-going process of N shifting from one form to another is collectively called the N cycle Soil Microbial biomass Plant biomass Can youCan you identify all theidentify all the N transformationsdifferent forms of N? and/or translocations?
  11. 11. Why do plants need N ?Nitrogen is an integral component of many essential plant compounds Amino acids 2.5 - 4% of Proteins enzymes Nucleic acids plant dry matter Chlorophyl
  12. 12. Old leaves first Evidence of N These symptoms Deficiency should not be used to identify when N is needed. yellowing (chlorosis) that Major irreversible starts at the tip yield loss has and moves in already occurred when these along the midrib symptoms are present
  13. 13. Nitrogenase: the key to biological N fixation
  14. 14. Added N often has no impact on legume yields Only way that N “fixation” can occur at low temperatures and pressuresSubstantial energy input is still required ~ 8 lbs of C per lb of N fixed Major constraint on legume yields
  15. 15. Legume nodules come inmany shapes and sizes
  16. 16. Legume inoculantscan be purchased in a variety of forms
  17. 17. Inoculation groups for commonly grown forage legumes. Alfalfa Group Alfalfa (Rhizobium meliloti) Black medic Bur clover Button clover White sweetclover Yellow sweetclover Clover Group Alsike clover (Rhizobium trifolii) Arrowleaf clover* Ball clover Berseem clover Crimson clover Hop clover Persian clover Red clover Rose clover* Subterranean clover* White clover Cowpea Group AlycecloverSoybean has its own inoculation group (Bradyrhizobium japonicum spp.) Cowpea Kudzu Peanut
  18. 18. Typical amounts of N fixed by forage legumes N fixed Crop (lb/A/year) Alfalfa 150-300+ Red clover 75-200 White clover 75-150Other annual forage 50-150 legumes
  19. 19. Not all legumes are efficient N fixers !Efficient N fixersforage legumes, soybeanscowpeas, peanutsInefficient N fixerssnap beansgarden peaslima beansOften responsive to added N
  20. 20. Some legumes (e.g., Styphnolobium affine) are not able to fix N symbiotically. Styphnolobium affine Some non-legumes (e.g., alder trees)fix N symbiotically with bacteria other than rhizobia. Some N fixing bacteria (e.g., azotobacter) are free-living - meaning that they do not need host plants.
  21. 21. CH4 Industrial Nprocess Haber-Bosch fixation invented over 100 yrs ago, refined but not replaced Where doesthe hydrogencome from??
  22. 22. Industrial N fixation is very energy intensive!> 700 GDF/ton NH3 Large improvements in energy efficiency were made during the 20th century. ~ 300 GDF/ton NH3 5.5 lbs N/GDF ~ 185 GDF/ton NH3 ~ 130 gallons of diesel fuel per ton of NH3 8.9 lbs N/GDF GDF = gallon of diesel fuel Fig. 6.12 in Smil (2001)
  23. 23. Nitrification inhibitors like N-serve disrupt the first step of this process Nitrification NH4+ NO2- NO3- Nitrification is actually a multi-step process NO2- is a toxic intermediate productWarm, aerated, near neutral conditions promote rapid nitrification
  24. 24. Nitrification is slower in cold soils
  25. 25. “If the industry is tocontinue the practice of fall N application, wemust police ourselves orrisk losing the option ofapplying nitrogen in the fall.”
  26. 26. “Being smart about the timing of anhydrous application canpay large dividends!WAIT UNTIL DAILY MAXIMUM SOIL TEMPERATURES AT4-INCHES ARE BELOW 50 DEGREES FAHRENHEIT.The rate of nitrification is significantly reduced when soiltemperature is below 50 degrees F, but microbial activitycontinues until temperatures are below freezing.In order to minimize risk, don’t apply nitrogen before the thirdweek of October in central Illinois, or the second week innorthern Illinois, even if air temperatures are getting cooler.In addition, do not use nitrogen or nitrogen with a nitrificationinhibitor if you live south of Illinois Route 16 or if soils areprone to leaching.”
  27. 27. Maximum soil temps under bare soils at 4” DOof I anhydrous U NOT APPLY application guidelines are basedYOUR WHEN on daily maximumIS RED! AREA temp at 4”Fall N application south of IL HWY 16 is never recommended by the U of I
  28. 28. Nitrification inhibitors are only cost-effective whenweather conditions occur that cause both significant nitrification and loss of nitrate Sample Date Dec. 8 Apr. 2 May 3 Application N-serve % NH4-N Remaining No 39 19 3 Nov. 7 (>50°F) Yes 63 28 17 No 40 33 7 Nov. 18 (<50°F) Yes 67 58 26
  29. 29. It is normally more efficient to apply N in the spring even if a nitrification inhibitor is used Spring w/o N serve Fall with N serve Fall without N serve
  30. 30. Impact of pH and N-serve on % nitrification Inhibitor = N-Serve w/o N serve w/ N serve% Nitrification High ph inhibits nitrification as Low ph can override N-serve much or more than N-serve Soil pH
  31. 31. Soil pH should be considered an important factor affecting the risks and benefits associated with fall applications of anhydrousammonia under climatic conditions found in the Corn Belt.Relatively rapid nitrification in higher-pH soils increases the potential for leaching and denitrification of NO–3 before plants begin rapid growth and uptake of N. N-Serve is probably a waste of money on low pH soils!
  32. 32. N2O (nitrous oxide) is an ozone depleter and potent greenhouse gas Denitrification NO3- NO2- NO N2O N2Warm, anaerobic conditions + OM promote rapid denitrification
  33. 33. Why is nitrate such a slippery character ? • Nitrate is an anion (i.e., negatively charged) • Nitrate compounds are very soluble • Nitrate is next in line as an electron acceptor when O2 is not present Denitrification
  34. 34. Immobilization
  35. 35. Net immobilization Net mineralization
  36. 36. SOM-N frequently does not become plantavailable fast enough for maximum yield Potential N uptake by wheat pasture Mineralized soil N Jenkinson
  37. 37. Well-fertilized the N often obtain Where does crops come frommore than half of their Ncrop ? that enters a corn from SOM Why Less more N tie-up ! uptake? Magdoff and Weil (2003)
  38. 38. What happens to fertilizer N ?100 So how were the scientists90 able to track the fertilizer N? Environmental losses during80 They used fertilizer spiked with N15! growing season Which N rate is likely to result in the most Measured after harvest leaching over the winter?
  39. 39. N rates applied to corn in the UShave been relatively stable for 3 decades 150 kg/ha = 134 lbs/ac
  40. 40. Corn yields have increased steadily since ~ 1940 160 bu/acre2010 1532009 corn crop = 165 bu/ac (national average) What do you think it will be this year?
  41. 41. As a result…Yield per unit of N has increased over the last 30 years ? lbs of grain per lb of N Some IL farmers consistently harvest more than 75 lbs of grain (1.3 bu) for each lb of N applied
  42. 42. Should N rates for corn be based on expected yield?Basing N rate on yield is logical - unfortunately optimal yield:N rate relationships vary widely from site to site and season to season
  43. 43. Relationship between optimal N rate and optimal corn yield in IL (72 site years)Only 13 out of 72 site-years in IL required more than 1 lb of N per bushel too high 96% of the time 1.2 : 1 line 1 : 1 line BOTTOM LINE There is no line that fits too high 82% this data well of the time Yield is a poor predictor of optimal N rate !!
  44. 44.
  45. 45. Can you believe prices werethis low just5 years ago?
  46. 46. Current version of the N rate calculator
  47. 47. Maximum return to N 0.20 when price ratio is 0.05PRICE RATIO
  48. 48. So why do you thinkThe N rate calculator uses regularly updateddata from regional N rate experiments and a the N rate calculator logical “Maximum Return to N” approach. is not more widely It is clearly more science based than yield based methods of setting N rates but is used? currently not used by many farmers.
  49. 49. So how do IL farmers manage N for corn?Each of you needs to collectanswers to these questionsfrom 2 farmers that differ in one of the following ways: > 50 yrs vs. < 40 yrs college vs. no college> 1000 ac vs. < 1000 ac
  50. 50. A few answers from last year
  51. 51. Why don’t most labs test for N ??? From the To the atmosphere atmosphere Crop 50 10-50 ? Fertilizer uptake 200 200 Soil organic matter 4000 160 80 NO3- + NH4+ Microbial biomass Loss by leaching Preseason mineral N a poor predictor of of Total soil N is also is a poor predictor 20-100 ? in season availability of N in humid regions in-season availability of N
  52. 52. Can we manage for thevariable amount of plantavailable N supplied by soil ?
  53. 53. PSNT = Pre-sidedress nitrate test LSNT = Late spring nitrate test
  54. 54. Nitrogen credits for the pre-sidedress soil nitrate test (PSNT) Soil yield potential Very high/high Medium/low PSNT value Nitrogen credit - - ppm N - - - - - lb N/a - - - > 21 Benefit from added N is unlikely 18-20 100 80 15-17 60 80 13-14 35 40 11-12 10 40 < 10 0 0
  55. 55. Researchers in many states(other than IL) have evaluated the PSNT and identifiedmodifications that work well for specific crops and locations
  56. 56. Comparison of the ISNT and PY methods for predicting sites where corn is nonresponsive to N fertilization. PY = Proven Yield method of determining N ratesites No. of nonresponsive for corn Sites predicted byManagement # N rate = Proven yield in bushels* 1.2 lbs of N/bushel Recommended of sites total PY ISNT system studied – manure or legume creditsManured 21 19 6 17within 1 yearContinuous 27 16 0 14cornCorn after 49 12 0 11soybeanCorn after 6 5 0 5alfalfaCorn after 2 0 0 0wheatTotal 105 52 6 47The 84 sites identified by crop rotation had not received manure for at least threeyears prior to the growing season studied.
  57. 57. Illinois Soil N test = Amino sugar testThe soil sample is treated with sodium hydroxide solution in aMason jar, then heated for five hours on a griddle at 48–50º C to convert amino sugar-N to gaseous ammonia. The ammonia is collected in boric acid-indicator solution and determined by titration.
  58. 58. Amino sugar N No response to additional N
  59. 59. No relationship betweenISNT and EONR EONR = economicallyoptimum N rate
  60. 60. Relationship between ISNT and total SOM in WisconsinStrong correlation of ISNT values to soil organic matter (OM) shows that the ISNT is probably measuring a constant fraction of soil organic N rather than a special mineralizable N pool 400 y = 12.9715 + 62.5734x 2 r = 0.88 n = 80 300 ISNT (mg kg-1) 200 100 0 0 1 2 3 4 5 Organic matter (%) University of Wisconsin-Madison Department of Soil Science 2006
  61. 61. Research in NYNitrogen (N) prices and environmental concerns have caused many corn(Zea mays L.) producers and advisors to rethink their current N managementpractices. These past 3 years, laboratory and field trials were conducted inNY to evaluate the performance of the Illinois Soil N Test (ISNT) in identifyingwhether or not additional N was needed. Initial test results showed the needfor temperature control in the laboratory and resulted in a modification of theprocedure to include enclosed boxes. Evaluation of the ability of the modifiedISNT procedure in detecting increases in organic N upon compost andmanure addition showed an increase in ISNT over time consistent with Ncredits from manure currently employed for N management in New York.However, to obtain an estimate of potential N release from readily availableorganic N sources, sampling should not take place within 4-5 weeks aftermanure (or fertilizers that contain ammonium) application or sod or covercrop plowdown or chemical kill.Results of the first 3 years of field trials showed that soilsamples taken to 20-cm (8 inch) depth and analyzed forboth ISNT and LOI-OM can be used to predict the need foradditional N for corn beyond starter fertilizer in New York
  62. 62. The ISNT has been discussed positively andnegatively in quite a few farm press articles over the last 5 years.
  63. 63.
  64. 64. GreenSeeker Technology
  65. 65. High N ratestrip needed
  66. 66. 6. How has using GreenSeeker impacted your farming operations? Do you thinkGreenSeeker saved you money either in cost savings or yield improvement?We were a little conservative with GreenSeeker the first year. We used it on 4,000 acres andreduced nitrogen application about 20 pounds an acre on average. We didn’t lose any yield. Youcouldn’t tell any yield difference between fields with lower nitrogen applications and our regularprogram, which averaged about 155 pounds. We saved at least 20 units across the board. Thetotal nitrogen savings was about $24,000. So I paid for the cost of GreenSeeker the first year.7. What would you tell a fellow farmer who was considering GreenSeeker?You have to trust what you are doing and have faith in the concept. Don’t go hog wild. Maybe onlydo half your crop the first year. And then you will see whether it will pay for itself. There are a lot oftimes when you are sidedressing (without GreenSeeker) and the crop doesn’t look like it needs it.The GreenSeeker takes the guesswork out of it.8. Any final thoughts on GreenSeeker.The overall concept behind GreenSeeker will be even more important in the future. If you can saveyourself a little bit on each farm, it adds up.Even though prices are good now, you still have to farm like your profit potential is poor. That is justgood business. The biggest way you can save money is with N.If there is a penny to be saved, I am going to save it. Those pennies here and there are what gotyou through when you were selling your corn for $2. The way nitrogen costs, we can’t afford towaste it.
  67. 67. Some GreenSeeker resultsfrom the IA Soybean Association On-Farm Network
  68. 68. What do you think this rig costs ?
  69. 69. How much N istaken up after tasseling? A lot!!!
  70. 70.
  71. 71. Most widely used N fertilizers
  72. 72. Ammonium phosphates Very high phosphorusMonoammonium 52% P2O5, 11% N, 100% analysis. Excellent materialphosphate (MAP) water soluble for use in starter fertilizer Most common phosphorusDiammonium phosphate 46% P2O5, 18% N, 100% fertilizer. Used extensively(DAP) water soluble as the basis for blended fertilizers Solid: 55% P2O5, 11% N Liquid form is very commonAmmonium polyphosphate Liquid: 34% P2O5, 10% N N and P fluid fertilizer
  73. 73. N fertilizer materials purchased in IL All #s are tons Material fall06 spring07MAP 11-52-0 6,955 4,017 10.5%DAP 18-46-0 56,653 42,147 10-34-0* 766 1,567 28-0-0 19,173 127,447UAN 22.5% 32-0-0 12,616 75,737Urea 46-0-0 10,136 23,480 3.2%AA 82-0-0 293,375 277,952 55 % 82.5-0-0 17,906 4830 98.8 % of material grade 1,043,307 94.6% of total N * (10-30-0, 10-32-0, 10-34-0, 11-33-0, 11-37-0)
  74. 74. Shift toward greater use of urea and UAN in the Midwest
  75. 75. Reasons for the decline in use of NH3 Concerns about human safety and impacts on soil Rail companies are raising rates and limiting transport of NH3 When application window is short, UAN is favored over NH3 Weather/soil conditions limit NH3 application window UAN application is faster and more flexible1-2 thousand acre/day for UAN vs. a few hundred acres for NH3 UAN can be applied with other crop inputs
  76. 76. Ammonia Hazards• Caustic (alkali) burns• Freezing burns• Inhalation danger to lining of mouth, throat and lungs• Does not support respiration – suffocation danger• Especially dangerous to eyes Agrochemicals and Security: Security and Anhydrous Ammonia Anhyd-06
  77. 77. Many anhydrous ammonia applicators giveuneven applications, particularly applicators with older manifolds. Manifold outlets across from the intake usuallyput out higher rates than outlets near the intake. When an older manifold is used, the mostimportant management practice is to randomize the hoses. This means that a row getting a low rate is more likely to be next to a row getting a high rate, which will minimize yield loss.
  78. 78. The Equaply system is only one of a number of good options for uniform anhydrous application on the market today!
  79. 79. Don’t ignore the N in DAP, MAP and starter fertilizer Nitrogen components of phosphorus (P) fertilizers can also be safely credited if they are spring-applied. Crediting half the N is safer if the P was applied in the fall before growth of a summer crop. Nitrogen components of starter fertilizers and nitrogen applied with herbicides should be included as part of the total intended N rate.
  80. 80. Urea (46-0-0)Urea should not be broadcast and left on the surfacefor extended periods.Missouri research has shown a 14 bu/acre yield penalty incorn (average of 38 experiments, mostly no-till) and a 5bu/acre yield penalty in wheat (average of 9 experiments)when urea is broadcast and not incorporated.Recommended methods of applying urea:• Treatment with Agrotain volatilization inhibitor beforebroadcasting.• Incorporation with tillage (within 3 or 4 days ofapplication).• Incorporation with irrigation (within 3 or 4 days).• Knife injection.
  81. 81. UAN (urea-ammonium nitrate) solution (28%–32% N) should not be broadcast on high-residue surfaces. Missouri research has shown a 25 bu/acre yield penalty when solution is broadcast in no-till corn (average of 20 experiments, mostly corn-soybean rotation). In tillage systems with less residue, less yield loss would be expected. Dribbling solution reduces contact between nitrogen and residue, and injection is best !
  82. 82.
  83. 83. • Effective• Efficient• Environmentally Smart Nitrogen
  84. 84. How many IL farmers actually use slow release N sources??? All of them! > 50% of the N taken up by corn is normally from OM
  85. 85. Recommended adjustments in N rates for legumes or manure
  86. 86. Less N is needed when corn is planted lateResearch at the Northern Illinois Research Center has shownthat less nitrogen fertilizer is required for most profitableyield when planting date is delayed.Based upon that research, U of I agronomists suggest that foreach week of delay in planting after the optimal date for anarea, the nitrogen rate can be reduced 20 pounds per acre -down to 80 to 90 pounds per acre as the minimum for verylate planting in a corn–soybean cropping system.Suggested reference dates are April 10 to 15 in southernIllinois, April 20 to May 1 in central Illinois, and May 1 to 10 innorthern Illinois.
  87. 87. So how well did you do ?The cornstalk nitrate test developed by Iowa StateUniversity (Iowa State Extension publication PM-1584, Cornstalk Testing to Evaluate NitrogenManagement) is a reliable way to evaluate your Nprogram at or near harvest. It cannot be used toguide N application rate, but can be used to tellwhether the N rate in a particular area was too low,optimal or excessive. Feedback gained from this testcan help producers improve rate decisions infollowing years.
  88. 88. Cornstalk nitrate testing 700-2000 ppm = optimum