Presentation on theme: "N Reservoir Biosphere (living organisms) Hydrosphere (water) Atmosphere (air) Geosphere Crust Soils and Sediments Mantle and Core MegaTons 2.8 x 10 5 2.3."— Presentation transcript:
N Reservoir Biosphere (living organisms) Hydrosphere (water) Atmosphere (air) Geosphere Crust Soils and Sediments Mantle and Core MegaTons 2.8 x x x x x x x % of Total Where is the N on planet earth ?? Most of the N is deep within the earth but very little of this N participates in biological cycles.
Reservoir/Pool Type Biosphere Hydrosphere Soil Atmosphere MegaTons 2.8 x x x x 10 9 % of Total Biologically relevant N % of BR N <0.01 < 1% ~ 8 % > 90 %
N has two stable isotopes, 14 N and 15 N. 14 N is much more abundant than 15 N 15 N labeling can be used to track the fate of added N
Why is N 2 so unreactive ??? N 2 is chemically unreactive at the temperatures and pressures of the hydrosphere, biosphere, and atmosphere because of its triple bond. This triple bond can only be broken under extreme temperatures and or pressures or in the presence of select enzymes.
Reactive N Reactive N Reactive N Reactive N
~ 5 MT ~ 20 MT ~ 30 MT ~ 85 MT > 90 MT
Human activities now dominate global cycling of reactive N
Nitrogen has many different oxidation states ! Species NameOxidation State NH 3, NH 4 + Ammonia, ammonium ion -3 N2H4N2H4 Hydrazine -2 NH 2 OHHydroxylamine N2N2 Nitrogen 0 N2ON2ONitrous oxide +1 NO Nitric oxide +2 HNO 2, NO 2 - Nitrous acid, nitrite ion +3 NO 2 Nitrogen dioxide +4 HNO 3, NO 3 - Nitric acid, nitrate ion +5 Organic N Well aerated soils Plant metabolism Poorly drained soils Most reduced Most oxidized C-NH 2
Do any of you remember this view ??? April 19, Alfred P. Murrah Federal Building Nitrate is a powerful oxidizing agent Ammonium nitrate + diesel fuel Why is this combination explosive ?
The on-going process of N shifting from one form to another is collectively called the N cycle Plant biomass Plant uptake Soil Microbial biomass
Why do plants need N ? Nitrogen is an integral component of many essential plant compounds Amino acids Proteins Nucleic acids Chlorophyl enzymes % of plant dry matter
Old leaves first Evidence of N Deficiency yellowing (chlorosis) that starts at the tip and moves in along the midrib These symptoms should not be used to identify where N is needed. Major irreversible yield loss has already occurred when these symptoms are present
Nitrogenase: the key to biological N fixation
Only way that N “fixation” can occur at low temperatures and pressures Substantial energy input is still required ~ 8 lbs of C per lb of N fixed
Legume nodules come in many shapes and sizes
Inoculation groups for commonly grown forage legumes. Alfalfa Group (Rhizobium meliloti) Alfalfa Black medic Bur clover Button clover White sweetclover Yellow sweetclover Clover Group (Rhizobium trifolii) Alsike clover Arrowleaf clover* Ball clover Berseem clover Crimson clover Hop clover Persian clover Red clover Rose clover* Subterranean clover* White clover Cowpea Group (Bradyrhizobium japonicum spp.) Alyceclover Cowpea Kudzu Peanut Lespedeza Joint vetch Lupine Group (Rhizobium lupini) Blue lupine White lupine Pea and Vetch Group (Rhizobium leguminosarum) Bigflower vetch Common vetch Hairy vetch Roughpea Winter pea Other**Bird’s-foot trefoil (Rhizobium loti) Cicer milk vetch Crown vetch Sainfoin (Rhizobium) Soybean (Rhizobium japonicum) Kura clover Leucaena Soybean has its own inoculation group
Amount of nitrogen fixed by various forage legumes Crop N fixed (lb/A/year) Alfalfa Red clover White clover Other annual forage legumes
Not all legumes are efficient N fixers ! Efficient N fixation forage legumes, soybeans cowpeas, peanuts Inefficient N fixation snap beans garden peas lima beans
NH 4 + Nitrification Nitrification is actually a multi-step process NO 2 - is a toxic intermediate product Warm, aerated, near neutral conditions promote rapid nitrification NO 3 - NO 2 -
Sample Date Dec. 8Apr. 2May 3 ApplicationN-serve% NH 4 -N Remaining Nov. 7 (>50°F) No39193 Yes Nov. 18 (<50°F) No40337 Yes Nitrification inhibitors are not 100% effective and are only cost-effective in some situations
NO 3 - NO 2 - NO N 2 O N 2 Denitrification Warm, anaerobic conditions + OM promote rapid denitrification
Why is nitrate such a slippery character ? Nitrate is an anion Nitrate compounds are very soluble Nitrate is next in line as an electron acceptor when O 2 is not present
Net mineralization Net immobilization
Jenkinson Mineralized soil N wheat pasture Potential N uptake by N is often a limiting nutrient
Where does the N come from ? Magdoff and Weil (2003) Well-fertilized crops often obtain more than half of their N from SOM Why more soil N?
Effect of tillage and crop on mineralizable N Adapted from Magdoff and Weil (2004) Mineralizable N declines during grass crops Mineralizable N increases during soybeans Sorghum Wheat Soybeans
What happens to fertilizer N ? Measured after harvest Environmental losses during growing season Which N rate is likely to result in the most leaching over the winter?
N rates applied to corn in the US have been relatively stable for 3 decades
Corn yields have increased steadily since ~ bu/acre
Weather often regulates crop productivity more than nutrient input rates in high productivity systems
lbs of grain per lb of N As a result… Yield per unit of N has increased over the last 30 years Some farmers consistently harvest more than 75 lbs of grain for each lb of N applied ?
Can we manage for the variable amount of N supplied by soil ?
Why don’t most labs test for N ??? Total soil N is also a poor predictor of in-season availability of N Preseason mineral N is a poor predictor of in season availability of N in humid regions Soil organic matter Microbial biomass NO NH 4 + From the atmosphere 50 To the atmosphere ? Fertilizer Crop uptake Loss by leaching ?
Soil yield potential Very high/highMedium/low PSNT valueNitrogen credit - - ppm N lb N/a > < 1000 Nitrogen credits for the pre-sidedress soil nitrate test (PSNT) Benefit from added N is unlikely
Researchers in many states have evaluated the PSNT and identified modifications that work well for specific crops and locations Click on this hot link:
Comparison of the ISNT and PY methods for predicting sites where corn is nonresponsive to N fertilization. No. of nonresponsive sites Sites predicted by Management system # of sites studied totalPYISNT Manured within 1 year Continuous corn Corn after soybean Corn after alfalfa 6505 Corn after wheat 2000 Total The 84 sites identified by crop rotation had not received manure for at least three years prior to the growing season studied. PY = Proven Yield method of determining N rate for corn Recommended N rate = Proven yield in bushels* 1.2 lbs of N/bushel – manure or legume credits
Illinois Soil N test = Amino sugar test The soil sample is treated with sodium hydroxide solution in a Mason 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.
Amino sugar N No response to additional N
No relationship between ISNT and EONR
University of Wisconsin-Madison Department of Soil Science 2006 Relationship between ISNT and total SOM in Wisconsin Strong 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 readily mineralizable N pool
Nitrogen (N) prices and environmental concerns have caused many corn (Zea mays L.) producers and advisors to rethink their current N management practices. These past 3 years, laboratory and field trials were conducted in NY to evaluate the performance of the Illinois Soil N Test (ISNT) in identifying whether or not additional N was needed. Initial test results showed the need for temperature control in the laboratory and resulted in a modification of the procedure to include enclosed boxes. Evaluation of the ability of the modified ISNT procedure in detecting increases in organic N upon compost and manure addition showed an increase in ISNT over time consistent with N credits from manure currently employed for N management in New York. However, to obtain an estimate of potential N release from readily available organic N sources, sampling should not take place within 4-5 weeks after manure (or fertilizers that contain ammonium) application or sod or cover crop plowdown or chemical kill. Research in NY Results of the first 3 years of field trials showed that soil samples taken to 20-cm (8 inch) depth and analyzed for both ISNT and LOI-OM can be used to predict the need for additional N for corn beyond starter fertilizer in New York
A & L Great Lakes Laboratories, Inc Conestoga Dr. Fort Wayne, IN (260) Cropsmith, Inc. 107 S. State St. Monticello, IL (217) AgVise Laboratories 604 Hwy. 15 W. P.O. Box 510 Northwood, ND (701) Midwest Laboratories B. St. Omaha, NE (402) Spectrum Analytic Inc. PO Box 639 Washington Court House, Ohio (740) (Ohio - local) (800) (Toll-Free) VH Consulting, Inc. 805 Lund St. N. Hudson, WI (715) Commercial labs that provide the ISNT There are several labs in the U.S. which currently run the amino sugar N test as part of their soil analysis services. By listing these labs we offer no endorsement of the labs. If you have questions about where to get your samples analyzed, please contact us for advice.
Getting Started With the New Illinois Soil Nitrogen Test Identify fields for sampling. a. Submit boundary file or plat map b. Sample will be taken on approximately 1.5 acre grids or by management zones. c. Soil samples will be taken from 0-12 inches and inches for organic nitrogen analysis. Submit field history and cropping plan. a. Improving nitrogen management relies on identifying the factors that are important for crop response and developing individual field recommendations. b. Initial rates will be conservative although in many cases may allow for substantial nitrogen savings. Review nitrogen soil map and application map. a. Apply nitrogen with variable rate applicator. b. Evaluation rates can be included in map so future rates can be adjusted for localized field responses. c. Map yields and analyze evaluation rates. ISNT map can be used for several corn crops. Use test strips to adjust to optimum economic nitrogen rate. With previous map as a guide, resample to improve accuracy of organic nitrogen test and to track any changes in test values.
A recent U of I study showed that high plant population is more important for high corn yields than nitrogen fertilizer on productive soils. The reverse was true on less-productive soils.
The ISNT has been discussed positively and negatively in quite a few farm press articles over the last several years.
High N rate strip needed
6. How has using GreenSeeker impacted your farming operations? Do you think GreenSeeker 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 and reduced nitrogen application about 20 pounds an acre on average. We didn’t lose any yield. You couldn’t tell any yield difference between fields with lower nitrogen applications and our regular program, which averaged about 155 pounds. We saved at least 20 units across the board. The total 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 only do half your crop the first year. And then you will see whether it will pay for itself. There are a lot of times 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 save yourself 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 just good 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 got you through when you were selling your corn for $2. The way nitrogen costs, we can’t afford to waste it.
Some GreenSeeker results from the IA Soybean Association On-Farm Network
What do you think this rig costs ?
Have any of you ever heard of the Soil Doctor system ?
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 1 : 1 line 1.2 : 1 line too high 96% of the time too high 82% of the time BOTTOM LINE There is no line that fits this data well Yield is a poor predictor of optimal N rate !!
Price ratio = 0.10
Maximum return to N when price ratio is 0.05 PRICE RATIO 0.20
Less N is needed when corn is planted late Research at the Northern Illinois Research Center has shown that less nitrogen fertilizer is required for most profitable yield when planting date is delayed. Based upon that research, U of I agronomists suggest that for each week of delay in planting after the optimal date for an area, the nitrogen rate can be reduced 20 pounds per acre - down to 80 to 90 pounds per acre as the minimum for very late planting in a corn–soybean cropping system. Suggested reference dates are April 10 to 15 in southern Illinois, April 20 to May 1 in central Illinois, and May 1 to 10 in northern Illinois.
It is better to apply N in the spring – even if a nitrification inhibitor is used
Soil pH % Nitrification Impact of pH and an inhibitor on % nitrification Inhibitor = N-Serve
Soil pH within the range of 6 to 8 should be considered an important factor affecting the risks and benefits associated with fall applications of anhydrous ammonia under climatic conditions found in the Corn Belt. Relatively rapid nitrification in the higher-pH soils increases the potential for early season losses of fertilizer N by leaching and denitrification of NO – 3 before plants begin rapid growth and uptake of N in June.
Most widely used N fertilizers in IL
Monoammonium phosphate (MAP) 52% P 2 O 5, 11% N, 100% water soluble Very high phosphorus analysis. Excellent material for use in starter fertilizer Diammonium phosphate (DAP) 46% P 2 O 5, 18% N, 100% water soluble Most common phosphorus fertilizer. Used extensively as the basis for blended fertilizers Ammonium polyphosphate Solid: 55% P 2 O 5, 11% N Liquid: 34% P 2 O 5, 10% N Liquid form is very common N and P fluid fertilizer Ammonium phosphates
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. Don’t ignore N in DAP, MAP and starter fertilizer
Many anhydrous ammonia applicators give uneven applications, particularly applicators with older manifolds. Manifold outlets across from the intake usually put out higher rates than outlets near the intake. When an older manifold is used, the most important 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.
The U of I recommends that no fall N applications be made south of Highway 16 in Illinois.
Urea should not be broadcast and left on the surface for extended periods. Missouri research has shown a 14 bu/acre yield penalty in corn (average of 38 experiments, mostly no-till) and a 5 bu/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 before broadcasting. Incorporation with tillage (within 3 or 4 days of application). Incorporation with irrigation (within 3 or 4 days). Knife injection. Urea (46-0-0)
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 !
Do you use any slow release N sources??? YES ! > 50% of the N taken up by corn is normally from OM
Recommended adjustments in N rates for legumes or manure
The cornstalk nitrate test developed by Iowa State University (Iowa State Extension publication PM- 1584, Cornstalk Testing to Evaluate Nitrogen Management) is a reliable way to evaluate your N program at or near harvest. It cannot be used to guide N application rate, but can be used to tell whether the N rate in a particular area was too low, optimal or excessive. Feedback gained from this test can help producers improve rate decisions in following years. So how well did you do ?
Cornstalk nitrate testing ppm = optimum
Recommended N application rates for small grains