Nitrogen A pop quiz!!! John Lamb SMBSC Grower Seminar Willmar, MN January 24, 2018
Question 1. Where is the largest pool of available N on earth? 1. Ocean 2. Atmosphere 3. Plants and Animals 4. Soil 5. Rocks and Mantle
Water, Water Everywhere and Not a Drop to Drink Atmosphere 78% N 99 % of available N! ~117,000 tons of N above each acre of land Chemically stable N 2, not available to plants
Question 2. The mineral form of nitrogen that sugar beet best utilizes is called. 1. nitrate 2. nitrite 3. ammonium 4. urea
Forms of N Absorbed by Plants Most N taken up by roots as inorganic ions NH 4 + (ammonium) and NO 3 - (nitrate) Limited uptake of small organic molecules Some NH 3 uptake through leaves
Forms of N Absorbed by Plants Relative amounts in soil of NH 4 + vs. NO 3 - depend upon soil conditions NO 3 - dominates in warm, moist, well-aerated soils Plant preferences Varies with plant species, cultivar, age Plant growth usually best with a mixture Plants adapted to acid soils grow best with NH 4 + High NH 4 + in plant can be toxic NH 4 + NH 3 Excess NO 3 - can be safely stored in vacuoles
Question 3. Nitrate is in the soil. 1. Mobile 2. Immobile
Nitrate is mobile, while ammonium is not! NO 3 - is mobile Mainly moves to plant roots by mass flow NH 4 + not as mobile Exchangeable cation Fixation in clay interlayers (like K + ) Moves by both diffusion and mass flow
Question 4. Nitrogen is in the plant? 1. Mobile 2. Immobile
Nitrogen Mobility N is mobile in plants Translocated from older leaves to younger leaves Deficiencies occur first on lower, older leaves
N Deficiency Corn
Deficiency in Sugar beet
Question 5. What is the guideline for N fertilizer application in the SMBSC growing area? 1. 70 lb N/A soil test N + fertilizer N 2. 110 lb N/A soil test N + fertilizer N 3. 150 lb N/A soil test N + fertilizer N 4. 200 lb N/A soil test N + fertilizer N
Question 6. What is the best depth to take a soil nitrate-n soil sample for sugar beet production? 1. 6 inches 2. 24 inches 3. 36 inches 4. 48 inches
Relative Return (%) Current Database for sugar beet N guidelines. 120 100 80 60 40 20 0 Sweet Spot 0 50 100 150 200 250 300 350 Soil Nitrate-N (0-4 ft) + Fertilizer N (lb/a) Current guidelines suggest a soil sample to a depth of 4 ft. plus fertilizer = 100 to 110 lb N/A.
Soil data after corn Look at 2-4 ft nitrate-n Soil depth 2011 2012 2013 2014 2015 2016 All inches ------------------------- lb N/A ------------------------- 0-6 11 17 20 14 19 28 18 6-24 23 27 42 40 30 53 36 24 42/48 24 25 34 51 38 43 36 0 42/48 58 70 96 105 87 125 90 lb N/A N rec 52 40 14 5 23 23 26 N applied 46 42 27 28 34 19 33 Remember, These numbers are averages!!!!
Nutrient Management Suggestions The suggested N fertilizer rate should be based on the organic matter of the zone. Soil organic matter level Total N (soil plus applied N) % lbs. N/A 0 - < 3 130 3 - < 4 120 4 - < 5 110 5-7 100 > 7 80
Only three more questions to go!
Question 7. On the average, how much nitrogen for sugar beet comes from the soil organic matter? A. 50 lb/a B. 125 lb/a C. 225 lb/a D. 500 lb/a
Average 125 lb/a Mineralization = lb N/A (soil with 5 % OM) Residual soil nitrate-n = 40 to 100 lb N/A Fertilizer =? So 125 + 110 lb N/A = 235 lb N/A 30 tons/a * 8 lb/ton = 240 lb N/A
Nitrogen Sources Atmospheric deposition Electrical discharges and industrial activities Soil organic matter N fertilizers Biological fixation Symbiotic Non-symbiotic Manure, compost, biosolids
Mineralization Release of organic N as plant available NH 4 N (inorganic N) 2-step process involving bacteria, fungi, actinomycetes Soil OM ~5% N ~1 to 4% of organic N mineralized each year Depends on temperature, moisture, aeration These affect microbial activity
Nitrogen Sources N sources for crop production include: Inorganic fertilizers Manure Other organic waste products
Question 8. What percent of cropland in the US is fertilized with manure? A. 0% B. 8% C. 16% D. 32%
Inorganic N Fertilizers Produced through N fixation Transformation of gaseous N 2 into plantavailable form Human / Industrial fixation N N
Industrial N Fixation Haber-Bosch process Most significant event of the 20 th century Huge effect on global food supply and human population
Industrial N Fixation N 2 reduced to NH 3 with high energy input High temperature and pressure Catalyst, 1200ºC, 500 atmospheres 3H 2 + N 2 2NH 3 NH 3 used directly or to produce other forms of N fertilizer
Major N Fertilizers Account for 70% of the fertilizer N used in the US Anhydrous ammonia Urea Urea-ammonium nitrate solutions
Question 9 and 10. How much fertilizer N is lost to denitrification in well-drained soils? A. 0% B. 25% C. 50% What about poorly drained soils? D. 75% E. 100% 6-55%
Gaseous losses of N Conversion of NO 3 - to N 2 and N 2 O Not the reverse of nitrification
Denitrification Where does it occur? Waterlogged soils Low O 2 microsites in soil Around roots or decomposing residues Denitrifying bacteria require OM Readily decomposable OM as an energy source C is oxidized, N is reduced
Denitrification Optimal Conditions: Favored by warm soil temperatures Does not occur below ph 5.0 Can cause significant N losses in poorly drained soils Denitrification in drainage and runoff water can reduce NO 3 - pollution potential
Denitrification N deficiency in wheat from denitrification losses
Bonus Question!!! How much does an acre of soil 6 inches deep weigh? A. 5000 lb B. 1,000,000 lb C. 2,000, 000 lb D. 3,000,000 lb
Calculations A soil that has a density of 1.0 g/cm 3 weighs 62.4 lb/ft 3. Most soils have a density of 1.3 g/cm 3 so 1.3 * 62.4 = 81.1 lb/ft 3 How many ft 3 in an acre 6 inches deep? 1 acre = 43560 ft 2 that times 0.5 ft (6 inches) = 21780 ft 3 So 81.1 * 21780 = 1,766,358 lb 2 million pounds would be a soil with a bulk density of 1.47 g/cm 3
End of Quiz Questions? Thank you!