1. Section 5.4 – Nitrogen Management
Nutrient Management
Section 5.4 – Nitrogen Management
Adapted CNMP Core Curriculum
Presented by:
Roberto Maisonnave, Ag Engineer & M. Sc.
International Environmental Consultant

2. Objectives
Nitrogen will be analyzed from the environmental concerns to agronomic benefits.
Nitrogen cycle: how management practices can impact its retention in the root zone for crop production.

3. Nitrogen in the Environment
Speaker Notes:
Assuming the audience is fairly well versed on the water cycle as it relates to nitrogen movement, use this slide to set the background that nitrogen can be leachable in the nitrate form, and on sandy soils can move to groundwater. In the holistic water cycle, that nitrate can come back into surface waters or contaminate wells. 10 ppm nitrate in drinking water is the health standard for groundwater. Forms of nitrogen from manure can also move via surface runoff, reaching waters of the state and causing fish kills. Either off-site movement of nitrogen forms in manure is unacceptable and a loss of nutrients for crop production.
Required Course Materials:
Supplemental Resources:
Suggested Learning Exercise:

4. NITROGEN CYCLE

5. Environmental Concern
Air quality: ammonia (NH3) and nitrogen oxides (N2O, NO) emissions
Water Quality
Ground Water - Leaching
Surface Water: Runoff & Tile drains

6. Agronomic Importance Most relevant macro-nutrient for plants
Most frequently deficient nutrient in crop production
N in soil solution: N-NH4 and N-NO3
Legumes can fix atmospheric N2 through microbial symbiosis (energy cost)
No benefit to overuse
Speaker Notes:
Nitrogen management of manure may be the one positive economic AND environmental factor for a producer to realize. There is no question that nitrogen is vitally important to economic crop production. Many crops show a direct correlation between nitrogen and yields. No producer ever wants to see yellow corn.
But, there is also no benefit for overusing N either via purchased fertilizer or over applications of manure. Manure nitrogen beyond the crop’s need, is a missed opportunity for that manure being used on another field, especially in times of high fertilizer prices. And it is a risk to the environment either via leaching, runoff, or volatilization. Most practices that recycle manure nitrogen to crop production are also the same practices that decrease the risk of loosing it to the environment.
Odor and air emissions will be reduced with incorporation/tillage/injection; Leaching can be mitigated by reduced rates and timing; Runoff to surface waters can be reduced by rates and timing combined with conservation measures; There is a concern for manures reaching tile drains, thereby traveling directly to surface waters.
Remind the audience that nutrient management inter-relates with conservation practices to mitigate losses to the environment. Examples might include cover crops to recycle nutrients over the winter, buffers to reduce runoff, tillage practices to increase residue thereby reducing erosion and or placement/tillage before, during and after manure applications.
Required Course Materials:
Supplemental Resources:
Suggested Learning Exercise:

7. N Agronomic Rate Concept
A rate of nutrient application on a field so that the amount of nitrogen required by a crop to grow is available, but minimizes the amount of nutrients that pass through the soil below root zone into the groundwater.
We can prevent leaching from happen but cannot be completely efficient about it. Soil Hydraulic Conductivity (k).
Spoon feeding?
Speaker Notes: TIMING OF APPLICATIONS IS CRITICAL
Required Course Materials:
Supplemental Resources:
Any local materials describing the nitrogen cycle could be included in the resource materials, depending on the audience’s background on this subject.
Suggested Learning Exercise:

8. Synchronization

9. Farming Limitations…

10. Nitrogen Recommendations for Crop Production
Speaker Notes:
At this point, begin discussions on specific nitrogen recommendations for crop production, as the requirement of the crop is the first step in determining manure rates.
Required Course Materials:
State specific nitrogen recommendations for relevant crops, generally published by the Land Grant University.
Supplemental Resources:
There may also be relevant bulletins from the University that discuss nitrogen in general and specifically as it is applied as fertilizer and/or manure. Bulletins that discuss the various forms of nitrogen in fertilizers can be helpful to the audience’s understanding of manure as a fertilizer.
Suggested Learning Exercises:

11. N Recommendations Traditionally, N uptake and yield
Variables that define N Crop Uptake:
Crop Type
Potential Yield
Risk of N losses
Timing of N supply
Soil Moisture
Weather conditions during crop season
Speaker Notes:
Traditional soil testing measures the soil for the amounts of P, K, micronutrients, pH, etc., but not nitrogen. Nitrogen recommendations are generally based on the crop to be grown and the yield goal. High potential yielding corn will require more N than a lower yield. Corn needs more than wheat; legume plants may not require any nitrogen as they make their own. The land grant university in each state has researched the yield potential of crops and has recommendation charts that are generally accepted in each state for CNMP development. These will probably be referenced in the state NRCS 590 standard.
Disclaimer: Corn will often be used as the crop to discuss Nitrogen as it is the most common across the nation. If another crop is more relevant to your area, please substitute that crop’s nitrogen requirements for your examples.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

12. Generalized Corn Yield Response Curve to Nitrogen
Economic N recommendation where yield drops off 95% of max yield.
Yield
12 ton/ha
10 ton/ha
8 ton/ha
6 ton/ha
4.5 ton/ha
2.5 ton/ha
Speaker Notes:
This is a typical general corn crop response curve to nitrogen showing that the greatest gains in yield are from the first units of N and a point is reached where the cost of additional N does not pay off in economic yield response. This curve, in general, is similar for many crops, but is specific for each crop. Most of these crop response charts have been developed with regard to economic yields related to nitrogen inputs, not based on environmental impacts. Obviously, when the crop doesn’t respond to the extra N there is a greater risk for losing the nutrient in the environment. The maximum agronomic yield is rarely the maximum economic yield. Most economic crop response curves have been developed for 95% of maximum yield.
Required Course Materials:
Suggested Resource Materials:
Many states will have charts specific to crops and yield goals showing nitrogen recommendations based on yield. Scanning or re-creating those charts would be a good substitute for this slide.
Suggested Learning Exercise:
Nitrogen fertilizer applied, kg/ha

13. Realistic Yield Potential
Example of NRCS 590 standards to determine yield potential
3 out of 5 years yield is achieved
50% of the time yield can be achieved
50% of the time yield is achievable plus 10% to allow for genetic improvements
Average over a number of years
Etc.
Speaker Notes:
Since yield potential is so critical to nitrogen recommendations, establishing “realistic” yield goals is important. Several methods of establishing yield goals are mentioned on the slide. The 590 standard often references one of these as being appropriate. Some 590 standards may say to take the last 5 years of harvest records, throw out the highest and lowest yields and average the remaining 3 years of yields. Others may state that selecting the yield goal that is achievable 50% of the time; maybe plus 10% to acknowledge improvements in varieties.
Whatever method is utilized, it should have a reasonable chance of being attained so nitrogen is not oversupplied.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

14. Requirement kg N /ton grain
How much N is needed?
Requirement kg N /ton grain
Expected Yield kg/ha
Needed
kg/ha
Extraction kg/ha
Corn 22
9.000
198
131
Wheat 30
5.000
150 99
Rice
22.2
6.000
133 88
Soybeans 80
4.000
320
240
Sunflowers 40
3.500
140 84
Speaker Notes:
Since yield potential is so critical to nitrogen recommendations, establishing “realistic” yield goals is important. Several methods of establishing yield goals are mentioned on the slide. The 590 standard often references one of these as being appropriate. Some 590 standards may say to take the last 5 years of harvest records, throw out the highest and lowest yields and average the remaining 3 years of yields. Others may state that selecting the yield goal that is achievable 50% of the time; maybe plus 10% to acknowledge improvements in varieties.
Whatever method is utilized, it should have a reasonable chance of being attained so nitrogen is not oversupplied.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

15. Current and Emerging N Recommendations
Nitrate-N tests
Organic Matter tests
Previous year manure applications
Economic Rates
Speaker Notes:
The best corn states are using forms of Nitrate-N soil tests (generally taken to 2 foot depths) and Organic Matter soil tests to assist in making Nitrogen recommendations. As the price of corn and nitrogen fertilizer prices fluctuate, there are also economic models available to estimate Nitrogen rates. With low corn and high fertilizer prices, these economic modes will produce N recommendations that are not only economical for, but also protective of the environment.

16. Nitrogen Availability and Losses from Manure
Manure Nitrogen Management should be profitable and Environmentally sound
Speaker Notes:
To fully understand how to utilize manure, and fertilizer, for that matter, an understanding of the nitrogen cycle is required. For this presentation, we will assume most people have a basic understanding, so we will concentrate on relating that knowledge to manure.
Required Course Material:
Supplemental Resources:
Any background material that describes the N cycle would be helpful to those in the class who are not familiar with it. It is assumed that participants have a working knowledge of the N cycle and this portion will relate those principles to manure nitrogen.
Suggested Learning Exercise:

17. Estimating Plant Available N from Manures
Book Values
MWPS, NRCS
State Specific Tables
Manure Tests
Speaker Notes:
One of several methods may be acceptable for estimating the plant available nitrogen from manures. They include manure testing, book values, (generally MidWest Plan Services or Natural Resource Conservation Service tables), state specific tables (often based on manure type and method of application for weather and conditions in specific locations), California has a salt index that relates to nitrogen recommendations and there are also current and emerging plant and soil testing procedures to measure nitrogen release from manures.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

18. Strategy Estimate manure rates on best judgment
Calibrate equipment to apply desired rate
Take representative manure samples at time of hauling
Take reputable N test in field if applicable
Follow through to yields
Evaluate and adjust for next season based on new manure tests and field observations.
Speaker Notes:
When you begin working with a producer, it may be similar to sitting in class today, you don’t have a current manure test, you cannot get one till the next time they empty the storage, but you cannot wait till then to begin laying the groundwork for the next application. The best option is to learn how to make the best judgment about estimating plant available N from a typical manure. Calibrate the equipment to deliver that rate, take a new manure sample the day the manure is hauled, conduct any in-field sampling that is recommended, follow through to determine if there are any yield losses and after evaluation of the above, use the new manure sample to recalculate, if necessary, the future manure application.
Required Course Materials:
Supplemental Resources:
Suggested Learning Exercise:
Estimating PAN by using math and common sense is valuable. Nitrogen is too dynamic and weather depended to accept these calculated rates at face value. Nitrogen deficiency is very obvious in fields and also directly correlates to yield losses. Especially for producers just beginning to credit manure nitrogen, it is important to follow up with in-field testing, observation and yield checks. Even for experienced users, in season tests will monitor losses of nitrogen due to weather.

19. Estimated Plant Available N (PAN)
Total N
Ammonium +
Organic
Estimated Plant Available N (PAN)
Estimating NH3 Volatilization
Most States have Tables
Season, weather, rain and Tº
Estimating organic mineralization
First year
From past manure applications
Speaker Notes:
Manure samples are generally tested for total nitrogen. Total N is made up of ammonium N and organic N. Some labs test for ammonium and some estimate it based on manure type. If a manure sample only provides the total nitrogen and the organic nitrogen, just subtract the organic from the total and the resulting answer will be ammonium nitrogen.
Our goal is to work with these two numbers and make an estimate of the plant available N.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

20. Mineralization Factor for first year
Mineralized Organic Nitrogen Source: MWPS
Manure Type
Manure Handling
Mineralization Factor for first year
Swine
Fresh
0.50
Anaerobic Liquid
0.35
Aerobic Liquid
0.30
Beef
Solid w/o bedding
Solid with bedding
0.25
Anaerobic liquid
Aerobic liquid
Dairy
Poultry
Deep pit
0.60
Solid with litter
Solid without litter
Speaker notes:
The Mineralization chart from Mid West Plan Services (MWPS) is one of the standards across the states. It estimates the amount of plant available nitrogen that will be mineralized from the organic portion of manure the first season after application. You can see that it is based on animal species and manure handling systems. On a manure sample, take the amount of organic N and multiply it by the estimated percent that will be mineralized the first season after application.
For example, if a manure test from an earthen manure storage on a diary farm (anaerobic) indicates 20 lbs. of N in the organic form, multiply this by 30% (20 lbs. organic x 0.30 = 6 lbs mineralized nitrogen in the first season. This portion is plant available.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

21. N Application Calculation Process (KS)
Not all the potentially PAN present in the soil is reflected on nitrate content lab test: N credits must be considered as potential sources.
These credits will be related to the field’s previous crop –only if a legume crop was raised- and previous year manure applications.
There will also be a minor adjustment based on the soil texture.

22. N Application Calculation Process (KS)
Credit Category
Description
Soil Texture Adjustment
1.0 for medium & fine textured soils
1.1 for sandy soils
Previous Year Manure
50 kg/ha N credit for last year application
20 kg/ha N if occurred two years ago
Previous Crop Adjustment
100 kg/ha N for Alfalfa
50 kg/ha N for Red Clover
30 kg/ha N for Soybeans
20 kg/ha N for fallow

23. Crop Nitrogen Requirement
Equation # 1: Crop Nitrogen Requirement
CNR = (YG x N Req x STA) – PCA – PYM – NST
where, 
CNR: crop nitrogen requirement (kg N / ha)
YG: yield goal (kg or ton / ha)
N Req: Nitrogen requirement (kg N / kg or Ton Grain)
STA: soil texture adjustment (no units)
PCA: previous crop adjustment (kg N / ha)
PYM: previous year manure application (kg N / ha)
NST: nitrogen soil test value (kg N / ha)
Red circle shows CREDITS

24. Crop Nitrogen Requirements
CNR (kg/ha) = (9 ton/ha * 22 kg N/ton*1)-(20 kg N/ha)-(50 kg N/ha)-(30 kg N/ha)
CNR (kg/ha) = 98 kg N/ha
Credits
Fine texture soil: F=1
Manure was applied last year
Previous crop is Soybeans
SNT reported 30 kg/ha for 0-60 cm

25. Effluent Application Rate
ETNC (mg/L) : (N-Org * 0.33)+(N-NH4*0.25)+(N-NO3 + N-NO2)
TKN: 491 mg/L
N-Org: 99 mg/L
N-NH4: 392 mg/L
MAV (L/ha): CNR (kg N/ha)* cf /ETNC (mg/L)
MAV (L/ha): (98 kg N/ha * ) / 130 mg/L
MAV (L/ha):
Max Application Rate: 75 mm-ha / ha
ETNC: effluent total nitrogen concentration

26. Balancing Math with Common Sense
Is this a good idea?
Infiltration rate of soils
Over application of other nutrients
Field and soil conditions
Environmental conditions
Speaker Notes:
An important point in manure applications is not only the agronomy side of rate/acre, but also the environmental side with relation to the soil’s ability to infiltrate and hold the volume of manure (water) applied. If an agronomic rate is too high for the soil to soak in and runoff occurs, then this is not the right rate. If it is so much that soil macro pores take the manure directly to the tile drain and the tile drain takes it to surface waters, then it is not the right rate. This same rate may be acceptable if it were applied in several applications over the season. But the lost opportunity of the nitrogen and the over application of other nutrients will still be a concern.
So far we have been assuming that the manure can and will be N-based.
As we move on to talk about phosphorus, you will learn that this isn’t always the case. But again, we start with N to see what the max rate is and then work our way down to specific needs of the farm.
Required Course Material:
Supplemental Resources:
Suggested Learning Exercise:

27. How do you know if you applied the rate you intended?
Calibrate!
Speaker Notes:
A lot of time has just been spent figuring out the plant available nitrogen. All of this hinges on either a known rate per acre of manure, or the ability to adjust the manure to a desired rate. In-field calibration cannot be stressed enough. If a producer indicates they have been applying manure at a given rate, and all the calculations hinge on this, without confirmation of the rate, assumptions could be leading to wasted time.
Required Course Material:
Bulletins and or websites for calibration may be provided to the audience.
Supplemental Resources:
Suggested Learning Exercise:

28. Nitrogen Management Summary
Realistic crop yield expectations
Accurate soil and manure tests
Equipment Calibration and Timing
Use common sense, field history observation, evaluation
Speaker Notes:
In summary, Nitrogen management requires a culmination of accurate soil testing, accurate manure sampling, calibration and common sense followed up with observation and evaluation in the field.