Module 8: Nutrient Management
8.1: Introduction to macro- & micronutrients
8.2: Nitrogen
8.3: Phosphorous
8.4: Potassium and other nutrients
8.5: Solid & liquid nutrients produced by AD
8.6: Environmental hazards & the case for nutrient separation
8.7: Phosphorous separation strategies
8.8: Nitrogen separation strategies
8.9: Salt removal & clean water technologies
8.10: Soil nutrients & soil health
8.11: Creation & implementation of cNMP
8.12: Data collection, reporting & compliance
This curriculum is adapted from: eXtension Course 3: AD, University of Wisconsin
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8.10: Soil nutrients & soil health
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Let’s start with soil
Farmers use nutrients to improve the agricultural quality of their soil: the ability of
that soil to support crop growth.
Physical properties of soil:
Color: generally, darker soil contains more organic matter
Texture: depends on the relative amounts of sand vs. silt vs. clay.
Structure: size of aggregates or crumb and the presence of soil pores that
allow water and air to penetrate soil
Internal drainage: deep penetration of water following saturating rains
Depth: distance from surface to the layer roots can’t penetrate
Susceptibility to erosion: is decreased by stable surface aggregates and effective
drainage
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Visual inspection of soil
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Chemical properties of soil
Chemical properties affect the availability of soil nutrients.
pH: measure of the relative acidity of alkalinity of a soil on a scale of 1 – 14
The scale is logarithmic, so a difference of 1 is 10-fold more or less acidic.
1 = acid
7 = neutral
14 = alkaline
Most Vermont soils are slightly acid, pH 5 – 7.
Most crops like neutral pHs of 6 – 7.
Cation exchange capacity: mineral nutrients are charged ions held in soil by
negatively charged clays and organic matter
+ Ca+2, Mg+2, K+1, Na+1, NH4+1
• CEC is a soil’s capacity to retain cations; increases with % clay & organics
Nutrients
• Primary macronutrients
• Secondary macronutrients
• Micronutrients
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Soil nutrients
Primary macronutrients
• Nitrogen: nitrate (NO3-1) & ammonium (NH4+1)
• Phosphorous: phosphates (H2PO4-1 & HPO4-2)
• Potassium (K+1)
Secondary macronutrients
• Calcium (Ca+2)
• Magnesium (Mg+2)
• Sulfur (SO4-2)
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Micronutrients
• Iron (Fe+2)
• Manganese (Mn+2)
• Boron (BO3-2)
• Molybdenum (MoO4-2)
• Copper (Cu+2)
• Zinc (Zn+2)
• Chlorine (Cl-1)
• Nickel (Ni+2)
• Cobalt (Co+2)
Soil biology
Healthy soils are full of life & microbes are particularly important.
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Components of the plant & soil ecosystem
A health plant – soil ecosystems requires attention to each of the components of
the system.
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Principles of soil fertility
1. Maintaining SOM by addition of organics + conservation of soil. For dairy
farms SOM is manure, cover crops, crop residues.
2. Maintaining soil biological activity / biodiversity of up to 100,000 different
organisms that feed on SOM & the by-product from roots. In return organisms
decompose organics, cycle & hold nutrients, degrade pollutants & improve
soil structure.
3. Maintain soil tilth, the porosity of soil that allows water, oxygen & roots to
infiltrate. Tilth depends on the aggregation of soil via organic matter from
roots & microbes & is reduced by compaction.
4. Preventing erosion by minimizing exposure to wind & fast-running water, and
maintaining SOM: cover crops, no/low till.
5. Maintaining proper soil pH in Vermont usually requires addition of lime. Soil
pH of 6 – 6.8 allows rhizome bacteria to thrive symbiotically with legumes.
6. Maintaining proper nutrient balance aimed at the crops being grown. Balance
is challenging when using manure whose NPK ratio is fixed.
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Soil compaction
There are three types of soil agricultural compaction:
1. Surface compaction is increased by growth of annual crops.
Surface crusting occurs when rain falls on bare soil creating a pore-less crust.
Surface compaction increases runoff & decreases germination.
1. Plow layer compaction is caused by erosion, reduced SOM, heavy field
equipment, and working wet soil.
2. Subsoil compaction occurs
below the tilled growing layer
when heavy equipment is
repeatedly run on (wet) soil.
Bottom line: Minimize traffic in
fields & don’t work wet soil.
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Goals that create good soil fertility
A healthy and balanced soil has the following characteristics:
• Good water infiltration & storage
• Good soil tilth (xxx)
• Low rates of erosion
• Good levels of organic matter
• High levels of biological diversity
• pH appropriate for the crop
• Essential nutrients for the crop of choice
It’s wise to choose a crop that the soil of a field can support and nurture.
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Cornell soil health test
Assesses twelve indicators of
biological, physical & chemical
soil properties.
More expensive than simpler
tests, but provides a great
baseline.
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8.11: Creation & implementation
of a cNMP
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What is nutrient management planning?
NMP is a mixture of best management practices that aims to:
1. Optimize crop yield & quality
2. Minimize fertilizer costs
3. Protect soil & water quality
How?
Apply:
• the right amount of fertilizer,
• In the right form,
• In the right place, and
• At the right time.
NMPs should satisfy state & federal regulations: Natural Resource Conservation
Service 590 Nutrient Management Standard – the highest standard of
excellence.
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NMPs focus on NPK
Nitrogen
• Essential part of chlorophyll
• Essential element for amino acid & protein production
• Lack of N causes yellowing of older leaves & stunted growth
Phosphorous
• Used to create healthy root systems
• Essential for formation of seeds & fruits (crop maturation); and
• Photosynthesis, respiration, cell division & other biological processes
• Lack of P causes stunted growth & purple or reddish coloration of older leaves
Potassium
• Regulates water use
• Aids with disease resistance
• Increases stem strength, photosynthesis & protein synthesis
• Lack of K causes scorching or necrosis & poor root systems
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Nutrient recommendations: sufficiency
There are a number of different approaches or philosophies to nutrient
recommendations
Sufficiency approach: based on maintaining a critical level of exchangeable
nutrients. Optimize soil nutrient levels to optimize crop production.
Maintenance approach: aims to replace the nutrients that the crop will remove from
the soil. This could allow you to calculate fertilizer need without testing soil.
Drawback: plants can take up more than they need if it’s there – luxury
consumption.
Soil cation approach: aims to maintain proper levels of K, Mg, Ca.
Problem: studies in the Northeast find that this approach is not effective.
Combination approach – just what it sounds like
All approaches should make use of tables of recommended nutrients for each crop
in each soil and location.
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Fertilizer calculations
Fertilizer nutrients are usually displayed as percentages of N-P2O5-K2O
So 12-24-12 is 12% N, 24%P, 12% K
Examples:
How many pounds of each nutrient are in 300 lb of 12-24-12?
N & K = (0.12) (300 lb) = 36 lb
P = (0.24) (300 lb) = 72 lb
Your grass hay field requires 100 lb of N per acre.
How much 46-0-0 urea do you need to spread per acre?
100 lb N = 217 lb of 46-0-0 should be spread per acre
0.46
Using the fertilizer table 20 on p.92 of “Digging In”, calculate the amount of muriate
of potash that should be spread if soil tests recommend spreading 150 lb of K2O
per acre for alfalfa?
150 lb = 246 lb of muriate of potash per acre
0.61
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Liquid fertilizer calculations
For liquid fertilizers percentages are still used, but the density of the liquid also
comes into play telling us how many pounds of nutrient there are per gallon.
Examples:
How many pounds of N,P,K are there in one gallon of a 9-18-9 liquid fertilizer with
a density of 11.4 lb?
N, K = 11.4 lb 0.09 N,K = 1 lb / gallon
1 gallon
P = 11.4 lb 0.18 P = 2 lb / gallon
1 gallon
So, if you want to apply 20 lb of P per acre as a starter fertilizer:
20 lb P
= 10 gallons of 9-18-9 per acre
2 lb P / gallon of 9-18-9
How much N and K will that add?
(10 gallons 9-18-9) (1 lb N and K/gallon) = 10 lb each of N & K
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How far can you afford to haul fertilizer?
Have a look at the worksheets in “Digging In” or the Excel version we prepared to
allow you to do quick spreadsheet estimates:
LINKS
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NMP software?
A variety of software tools are out there.
• UVM likes goCrop, a web application
• ACS (Agricultural Conservation Services) uses Crop and Field
• Sosten Lungu, our agronomy professor, likes to use a variety of tools:
• Purdue’s Manure Manager
• RUSLE2
• simple Esxcel spreadsheets
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First, get organized!
You might consider creating a real or virtual binder of information organized to
flow with the NMP process:
• Farm information
• Maps (six types!)
• Soil information
• Soil analysis
• Manure production
• Manure analysis
• Field & crop information
• Risk assessment (Vermont P Index)
• Field-by-field planning
• Record keeping
• References
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Six types of maps
1. Proximity map: all tracts of land used by the farm in relation to the farmstead,
town and roads
2. Conservation plan map: FSA (Farm Service Agency) land tract & field
numbers for any farm involved in a federal program
3. Nitrate leaching map: highlighting fields prone to leaching because of soil type
4. Topographic map
5. Environmental concern map: showing environmentally sensitive areas or land
features: water, wetlands, wells, wildlife habitat, rare and threatened species
6. Soils map: showing which of Vermont’s 180 soil types are found in each field
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Proximity map
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Conservation map
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Nitrate
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Topographic
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Enviro
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Soils
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Soil fact sheets
USDA NRCS offers a
Vermont Soil Fact Sheet
for each of the 180 types
of soil found in Vermont.
• Find and download a
soil fact sheets for each
type of soil on your
farm.
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Soil sampling
The key to good soil sampling is being sure that your sample is representative of
the entire field. Sampling must be repeated every three years.
1. Take samples in the fall.
2. Use a sampling probe or auger.
3. For each field that you plant and fertilize as a unit, take 15 sample cores per
20 acres and combine in a 5-gallon bucket to create a composite sample.
If the field is greater than 20 acres, take 2 composite samples (30 cores).
If parts of a field are distinctly different, create a sample for each part.
a. Use 6 inches for hay or perennial crops.
b. Use 6-10 inches for corn or annual crops.
4. Discard plant material & mix all cores well.
5. Place about 1 cup of the mixture into a plastic bag.
6. Label with name, field name, sample number & date.
7. Log the sample, recording field, sample location & date.
8. Send the samples for testing.
9. Organize the results in a spreadsheet that can be sorted for trends.
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Soil erosion
Erosion: when soil loses its structure an travels from one place to another by
wind, rain or surface water.
Types:
1. Sheet erosion: removal of a uniform layer from bare soil
2. Rill erosion: in channels formed by the concentrated flow of water
3. Gulley erosion: formation of large channels (or rills) over time
T value = tolerable soil loss in units of tons of soil per acre per year
• T values are the amount of soil that can be formed (and therefore
lost) per year to maintain steady soil levels.
• Shown on the soil fact sheet
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RUSLE2
RUSLE2 = revised universal soil loss equation version 2
A complex computer model that estimates potential soil losses from rill & interrill
erosion caused by rain and surface water.
• Considers many factors
RUSLE2 reports should be run for each field and will suggest management
strategies and the loss of soil predicted for each.
• Goal: soil loss less than T
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Create a field inventory with software
Use realistic crop yields based on a good historic average!
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Manure application schedule
Is a working plan organized by crop and month
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Management for N or P?
This decision is made using using two tools: 1) the P index, and 2) soil P tests.
In a perfect world, we could create the perfect fertilizer for each and every field to
be ensure that each field received sufficient nutrients, but never more than it
needed. This would prevent nutrient loss and pollution of water.
But the world isn’t perfect, and in the real world we must find the most effective
and least risky way to use manure and digester effluent as a source of recycle
nutrients back into the food system.
N-based or P-based management?
How do we do this well? If the P index is too high, nutrient application must
manage P, even if it prevents application of sufficient N. Under P-based
management, any P applied to a field must be removed by the crops grown in
that field. However, if the P index is low and soil can handle additional P, then
nutrient application can ensure that fields receive as much N as they need.
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N- or P-based nutrient management
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A example:
A field is given a “yellow” rating: it has a high P index & soil P levels of greater
than 20 ppm. So, this field must be managed for P.
Cropping plan: corn silage with a yield of 20 tons/acre (based on previous years
or similar conditions)
How many tons of P are removed per acre by corn silage?
(20 tons) (5 lb P removed / ton) = 100 lb
So how much P can you apply in spreading manure or AD effluent? 100 lb
How much manure or effluent will supply 100 lb of P?
On average your manure has a P concentration of 8 lb / 1000 gallons, so:
(8 x 12) = 96 (pretty close to 100)
(12) (1000 gallons) = 12,000 gallons of manure per acre
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8.12: Data collection, reporting
& compliance
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What records should you keep?
Records should be kept on a per field basis.
1. Planting & harvest dates
2. Crop yields
3. Dates and amounts of all nutrients applied (type, amount, method)
For the cNMP you must have copies of:
• Updated copy of your cNMP
• Copies of current soil tests
• Copies of current manure / effluent tests
• Records of any manure transferred off-farm
Keep old files on hand for at least five years.
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How do you measure crop yields?
Methods used include:
• Weighing truckloads or wagonloads using truck scales
• Measuring wagonloads
 Volume of each wagon
 Samples of each day’s harvest for dry weight
 U Wisconsin found that when forage dry weights were from 30 –
50%, density of forage crops could reasonably be estimated as
5 lb dry matter / cubic foot
Example:
A wagon is 16 ft long x 7.25 ft wide x 6 ft high = 696 ft3
DM estimate = (696 ft3) (5 lb DM / ft3) = 3,480 lb DM / wagon = 1.74 tons DM
If actual DM is 28%, actual mass = 1.74 tons / 0.28 = 6.96 tons/wagon
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Darby (2009); Sid Bosworth @ UVM Extenesion
Who has state reporting requirements?
Farm size and operations determine how they are regulated in Vermont:
Medium Farm Operations
Large Farm Operations
MFO
LFO
Mature dairy
(milking or dry)
200 - 699
700
Beef or cow/calf
300 - 999
1000
Youngstock / hiefers
300 - 999
1000
horses
150 - 499
500
turkeys
16,500 – 54,999
55,000
Laying hens
25,000 – 81,999
82,000
Annual reporting using MFO or LFO forms
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EQIP may be able to help
EQIP, the Environmental Quality Incentives Program, is administered by NRCS
as a voluntary conservation program.
• Aims to combine agricultural production & environmental conservation
• Offers financial & technical help for implementation of structures or
management practices.
• EQIP eligibility requires complete NRCS crop records for the previous year.
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Recordkeeping cheat sheets
Consider maintaining a summary sheet or log of:
• All discrepancies between your plans and what you actually did;
• Extraordinary weather;
• Unexpected events, both good and bad;
• Keeping this log in chronological order makes it easier to piece together
events long after they’ve happened.
Don’t forget to document implementation of measures required or requested by
the state after your previous report.
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Updating the cNMP
Annual updates are critical and are easier to do if you’ve kept a cheat sheet of
log, and if you tackle one section of the cNMP at at time:
Farm Information Sheet:
Has herd size changed? Has acreage used changed? Borrowing or leasing new
fields? Has the crop plan or rotation changed? Have tilling methods or spreading
methods changed?
Maps & soil information can be changed by NRCS / NRCD, so give them
information about fields added or removed and give them time.
Soil analysis must be done every three years, so check dates, send in new
samples, archive old information and add new results.
Manure production: Have you added new animals or changed storage?
Manure analysis needs to be done annually, so send out the sample and update
that portion of the cNMP.
Field information: update the crop history & yield section.
Field-by-field planning must be updated if you’ve taken new soil tests.
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cNMP resources
www.uvm.edu/extension/cropsoil/soil-healt-and-nutrient-management
www.uvm.edu/pss/vtcrops/articles/VT_Nutrient_Rec_Field_Crops_1390.pdf
pss.umv.edu/ag_testing/
www.vt.nrcs.usda.gov
www.vt.nrcs.usda.gov/soil/so_stat.html
efotg.nrcs.usda.gov/treemenuFS.aspx?Fips=50001&MenuName=menuVT.zip
www.vt.nrcs.usda.gov/technical/Nutrient_Management/
www.vermontagriculture.com/ARMES/awq/AAP.html
www.vermontagriculture.com/ARMES/awq/MFO.html
www.vacd.org
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This curriculum is a modification of the wonderful:
• eXtension Course 3: AD, University of Wisconsin
http://fyi.uwex.edu/biotrainingcenter/online-modules/series-three-anaerobic-digestion/
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