Nitrogen A pop quiz!!! John Lamb SMBSC Grower Seminar Willmar, MN January 24, 2018

Size: px
Start display at page:

Download "Nitrogen A pop quiz!!! John Lamb SMBSC Grower Seminar Willmar, MN January 24, 2018"

Transcription

1 Nitrogen A pop quiz!!! John Lamb SMBSC Grower Seminar Willmar, MN January 24, 2018

2 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

3 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

4 Question 2. The mineral form of nitrogen that sugar beet best utilizes is called. 1. nitrate 2. nitrite 3. ammonium 4. urea

5 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

6 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

7 Question 3. Nitrate is in the soil. 1. Mobile 2. Immobile

8 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

9 Question 4. Nitrogen is in the plant? 1. Mobile 2. Immobile

10 Nitrogen Mobility N is mobile in plants Translocated from older leaves to younger leaves Deficiencies occur first on lower, older leaves

11 N Deficiency Corn

12 Deficiency in Sugar beet

13 Question 5. What is the guideline for N fertilizer application in the SMBSC growing area? lb N/A soil test N + fertilizer N lb N/A soil test N + fertilizer N lb N/A soil test N + fertilizer N lb N/A soil test N + fertilizer N

14 Question 6. What is the best depth to take a soil nitrate-n soil sample for sugar beet production? 1. 6 inches inches inches inches

15 Relative Return (%) Current Database for sugar beet N guidelines Sweet Spot 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.

16 Soil data after corn Look at 2-4 ft nitrate-n Soil depth All inches lb N/A / / lb N/A N rec N applied Remember, These numbers are averages!!!!

17 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 - < < < > 7 80

18 Only three more questions to go!

19 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

20 Average 125 lb/a Mineralization = lb N/A (soil with 5 % OM) Residual soil nitrate-n = 40 to 100 lb N/A Fertilizer =? So lb N/A = 235 lb N/A 30 tons/a * 8 lb/ton = 240 lb N/A

21 Nitrogen Sources Atmospheric deposition Electrical discharges and industrial activities Soil organic matter N fertilizers Biological fixation Symbiotic Non-symbiotic Manure, compost, biosolids

22 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

23 Nitrogen Sources N sources for crop production include: Inorganic fertilizers Manure Other organic waste products

24 Question 8. What percent of cropland in the US is fertilized with manure? A. 0% B. 8% C. 16% D. 32%

25 Inorganic N Fertilizers Produced through N fixation Transformation of gaseous N 2 into plantavailable form Human / Industrial fixation N N

26 Industrial N Fixation Haber-Bosch process Most significant event of the 20 th century Huge effect on global food supply and human population

27 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

28 Major N Fertilizers Account for 70% of the fertilizer N used in the US Anhydrous ammonia Urea Urea-ammonium nitrate solutions

29 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%

30 Gaseous losses of N Conversion of NO 3 - to N 2 and N 2 O Not the reverse of nitrification

31 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

32 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

33 Denitrification N deficiency in wheat from denitrification losses

34 Bonus Question!!! How much does an acre of soil 6 inches deep weigh? A lb B. 1,000,000 lb C. 2,000, 000 lb D. 3,000,000 lb

35 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 = ft 2 that times 0.5 ft (6 inches) = ft 3 So 81.1 * = 1,766,358 lb 2 million pounds would be a soil with a bulk density of 1.47 g/cm 3

36 End of Quiz Questions? Thank you!