Agricultural Pollution: Fertilizers, and Animal Manure

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Agricultural Pollution Fertilizers, and Animal
Manure

• Textbook Chapter 26.3
• and 27.7 - 27.11

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Part 1. Fertilizer N and P impacts on
groundwater and surface waters
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Voter guide

• http//pollfinder.sos.state.mn.us/
• Vote Tues. Nov. 3

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POLLUTION FROM FERTILIZERS

• Nitrate in ground and surface waters
• P in surface waters
• Contamination from accidents.
• Spills
• Fires.

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Types of N fertilizer

• Anhydrous ammonia, NH3(g)
• Urea, (NH2)2CO
• Ammonium nitrate, NH4NO3
• Ammonium sulfate, (NH4)2SO4
• Solutions containing, urea, ammonium nitrate,
  and/or ammonium sulfate.

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Reactions of N fertilizers

• Dissolution of ammonia gas
• NH3 H2O --gt NH4OH
• Rapid enzymatic hydrolysis of urea (urease).
• (NH2)2CO 2H2O --gt 2(NH4)2CO3
• Nitrification
• NH4 2O2 --gt NO3- H2O 2H
• Note that ammonium fertilizers acidify soils
• This is greater than the effect of acid rain on
  agricultural soils.

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Other reactions of N in soil.

• Fixation of inorganic N2 to NH4
• By N-fixing organisms (e.g. legumes)
• Mineralization of organic N to NH4
• Binding of NH4 to cation exchange sites.
• Immobilization of N by microbes in high C/N
  organic materials (e.g. Grain straw)
• The C/N ratio of microbes is in the range of 5 to
  10.
• Organic materials with C/N greater than 30 will
  tie up N during decomposition.
• Organic materials with C/N less than 25-30 will
  release N during decomposition.

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Mobility of N in soils

• NH4 retained by cation exchange sites.
• NH4 is oxidized in aerobic soils to nitrate.
• Nitrate is very mobile
• KD is about zero.
• Retardation factor is about 1.
• If nitrate in a soil is in excess of that taken
  up by plants it can be leached to ground water.

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Nitrate pollution of ground water

• The regulatory limit of nitrate in ground water
  is 10 mg/L nitrate N.
• Nitrate is causes blue baby syndrome.
• Similar for young pigs.
• Is often very high in shallow ground waters where
  irrigated crops are grown on sandy soils
• E.g. Corn in western Nebraska
• Potatoes in Wisconsin and Minnesota.
• Has historically been a problem in the Karst
  region of SE Minnesota.

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Risk

• IRIS
• http//www.epa.gov/iris/subst/0076.htm
• Most cases of infant methemoglobinemia are
  associated with exposure to nitrate in drinking
  water used to prepare infants' formula at levels
  gt20 mg/L of nitrate-nitrogen (Bosch et al., 1950
  Walton, 1951 Sattelmacher, 1962 Simon et al.,
  1964 ECETOC, 1988). Cases reported at levels of
  11-20 mg/L nitrate- nitrogen are usually
  associated with concomitant exposure to
  bacteriologically contaminated water or excess
  intake of nitrate from other sources

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Nitrate pollution of ground water(cont.)

• N fertilization is generally only 30 to 70
  efficient.
• Some of the excess can be lost to groundwater as
  nitrate.

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Percentage of wells exceeding 10 mg/L nitrate N
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How to minimize losses to ground water?

• Use best management practices (BMPs)
• Dont over fertilize.
• N has been cheap
• But price goes up with natural gas prices.
• Growers generally add extra to cover the
  eventualities of excess leaching due to unusually
  high rainfall, etc.
• Add N at the time of crop demand.
• Can use fertigation but in Minnesota this can
  result in irrigation after a rainfall.

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Phosphate fertilizers

• Super phosphate
• Sulfuric acid treated phosphate rock (apatite)
• Ca(H2PO4)2 plus CaSO4 2H2O (gypsum)
• Triple superphosphate
• Phosphoric acid acid treated phosphte rock
  (apatite)
• Mostly highly soluble Ca(H2PO4)2

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Most P is immobilized in soils

• H2PO4- and HPO42- ions adsorb strongly in soil
  particles.
• Phosphate precipitates with Ca, Al, and Fe.
• Not generally a threat to ground water except in
  heavily fertilized peat soils (e.g. in the
  Everglades in Florida) and poor sandy soils with
  shallow ground water.
• Moves with soil particles into surface waters.
• As little as 0.02 mg/L of P can result in
  increased algal growth in surface waters.

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Decreasing P pollution

• Soil test. Dont over apply.
• Farmers as well as people growing turf need to
  test.
• Most home owners in the Twin cities have over
  applied P (and under fertilize with K). New P
  rules say you have to have a soil test if you
  want to apply P to a lawn
• Prevent erosion.

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Part 2. N and P pollution from manure and
prevention methods
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In traditional mixed farming manure was an asset
for crop production

• Number of animals was small.
• Nutrients in manure could easily be returned to
  the fields where the crops were grown
  (recycling).
• However, poor handling of manure sometimes did
  result in contamination of wells with nitrate and
  disease organisms.
• Manure piles too close to wells
• Problem in Karst area of SE Minnesota
• Manure piles near sinkholes
• Nitrate pollution of ground water.

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Manure is an asset for modern smaller animal
producers who grow most of their feed

• Can recycle the nutrients

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Manure is a liability for large scale specialized
farming

• Large animal operations.
• Thousands of cattle and hogs
• Hundreds of thousands of poultry
• Concentrated Animal Feeding Operation (CAFO)
• E.g. 10,000 hogs produce about as much waste a
  20,000 people.
• Growers cannot afford a full scale municipal
  sewage plant.
• May be insufficient crop land nearby to utilize
  the nutrients in the manure.

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Non point source

• Unlike industrial and sewage plant point sources
  of pollution most of the adverse effects of
  manure are as nonpoint sources.

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Manure production by farm animals
Adapted from (Moore and M.J. Gamroth, 1993)
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N, P, and K content of fresh manure (dry weight
basis)

• Total
• Elements Type of
  Waste_(byproduct)____________
• Cattle (steer) Swine Cage layer Broiler Dairy
• N, 3.2 3.8 4.8 4.75 2.4
• P 1.6 2.13 2.22 2 0.76
• K 0.5 1.34 1.63 1.38 0.75
• Note Calcium phosphate generally added to swine
  rations

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Manure is an important source of plant nutrients
in Minnesota
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Problems with Manure

• Air quality (a point source)
• Anaerobic gases
• CH4
• NH3
• H2S
• Other odorous volatile acids and S compounds.
• Water quality
• Poor handling and storage or spill (point source)
• From manure spread on land (non point source)
• P to surface waters
• N to surface and ground waters
• Fecal coliform

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Potential for nitrate and fecal coliform
contamination of wells,
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Storage is very important for best use of plant
nutrients in manure

• Should apply nutrients to meet the needs of the
  crop. Timely application is important.
• Storage facilities are expensive.
• The less expensive open storage facilities have
  large odor problems.
• Earth structures subject to breakage.

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Waste flow in a large dairy operation in SW
United States
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Earthen aerobic storage pond Fig. 26-15a
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Earthen anaerobic storage pond, Fig. 26-15b
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Costs of different types of manure storage

• Types of Storage Structure Approximate cost/1000
  gallon of storage capacity1/
• Unlined (natural) earthen basin 36
• Clay-lined earthen basin using clay on site
  70
• Earthen basin lined with plastic liner
  (geosynthetic membrane) 76
• Round, above-ground tank constructed of poured in
  place concrete 163
• Above-ground, glass-lined tank 198
• 1/ Cost estimates based on 50,000 gallon storage
  capacity. Cost per 1000 gallon will decrease
  significantly for larger storages.

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Nutrient losses in storage

• In well constructed storage facilities P and K
  losses are generally less than for N.
• N losses can be very significant.
• Ammonia volatilization
• Nitrification followed by denitrification.
• Leaching and runoff (also a problem for P and K)

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Nitrogen losses with different manure handling
systems

• System Nitrogen lost,
• Solid
• Daily scrape and haul 15-35
• Manure pack 20-40
• Open lot 40-60
• Deep pit (poultry) 15-35
• Liquid
• Anaerobic pit 15-30
• Above-ground storage 10-30
• Earth storage 20-40
• 
  aAdapted from MWPS (1985)

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Nutrient utilization as a part of waste
management planning

• In Minnesota large animal operations must have a
  nutrient management plan and have sufficient land
  available to utilize the plant available N in the
  animal waste produced.
• N based planning generally results in the
  application of P in excess of the crop removal.
• P is now a concern and if P soil test values are
  too high manure application is prohibited
• P soil tests increase with continued use of
  manure .
• New P index will give guidelines based on risk to
  surface waters.

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Nutrient removal for corn and soybeans. (total
above-ground portion)

• Crop Yield N P2O5 K2O
• ------------lb/acre------
  ---------
• Corn 150 bu 185 80 215
• Soybeans 30 bu 123 32 52

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Compare with N, P, and K content of fresh manure
(dry weight basis)

• Total
• Elements Type
  Waste_____________
• Cattle (steer) Swine Cage layer Broiler Dairy
• N, 3.2 3.8 4.8 4.75 2.4
• P 1.6 2.13 2.22 2 0.76
• K 0.5 1.34 1.63 1.38 0.75
• Note Calcium phosphate generally added to
  swine rations

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Compare N/P ratios

• Corn Plants
• P2O5 44 P
• 80 lb/ac P2O5 35.2 lb/ac P
• N/P 185/35.2 5.2
• Steer manure
• N/P 3.2/1.6 2.0

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Nutrient utilization as a part of waste
management planning ( cont.)

• N regulations are designed to minimize nitrate
  pollution.
• All of the inorganic N (ammonium plus nitrate) is
  considered plant available. (e.g. liquid dairy
  manure about 30 of N is ammonium)
• Must have manure analysis to determining how much
  plant available N is applied with manure

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Nutrient availability

• A factor is used to estimate the availability of
  N in the organic fraction.

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Amount of organic nitrogen mineralized during the
first cropping season (Minn. BMPs)

• Manure Type Manure Handling Mineralization Factor
• Swine Fresh 0.50
• Anaerobic liquid 0.35
• Aerobic liquid 0.30
• Beef Solid without bedding 0.35
• Solid with bedding 0.25
• Anaerobic liquid 0.30
• Aerobic liquid 0.25
• Dairy Solid without bedding 0.35
• Solid with bedding 0.25
• Anaerobic liquid 0.30
• Aerobic liquid 0.25
• Sheep Solid 0.25
• Poultry Deep pit 0.45
• Solid with litter 0.30
• Solid without litter 0.35

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N losses can occur after application

• Avoid runoff and volatile losses after
  application
• Knife in liquid.
• Broadcast liquid or solid followed by immediate
  plow down.

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Average nitrogen losses by method of application
and manure type

• Percent of nitrogen applied that is lost with 4
  days of application.
• Application method Type of waste
  Nitrogen lost,
• Broadcast Solid 15-30
• Liquid 10-25
• Broadcast with Solid 1-5
• immediate cultivation Liquid 1-5
• Knifing Liquid 0-2
• Sprinkler irrigation Liquid 15-35
• aAdapted from MWPS (1985)

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Nutrient availability, P and K in manure

• The availability of P and K is similar to
  fertilizer P and K.
• Lab results are often given as P2O5 and K2O.
• Multiply P2O5 by 0.44 to get P and K2O by 0.83 to
  get K.

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Development of guidelines to minimize excessive P
accumulation in soils

• States are developing guidelines to minimize
  excessive P on soils.
• Nutrient management plans required for CAFOs
• Also some restrictions are linked to various farm
  programs
• Some states limit the application of any form of
  P in excesses of crop removal when soil test
  values are already high.

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Development of guidelines to minimize excessive P
accumulation in soils (cont.)

• May prohibit application above a higher defined
  level soil test. (prohibition of manure).
• The latest efforts in Minnesota and Wisconsin are
  to include susceptibility to erosion and
  proximity to surface waters in future guidelines.
  
• Phosphorus index is being developed.

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Current limits on P for nutrient management plans

• Bray P test gt75 lt 150 ppm Add P only to meet
  crop needs.
• Bray P of gt150 no P source including manure

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Concern for Cu and As additions to feed

• As added in poultry antibiotics.
• Cu added to swine feed.
• These accumulate in the manure
• Compared to the 503 sludge rules these elements
  are not yet a serious threat.

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Arsenic in poultry manure and copper in hog
manure are potential problems.

• EPA 503 cumulative site life loading rates for
  metals in sewage sludge (Class B Biosolids)
• Element Loading rate (lb/acre)
  
• Arsenic 37
• Cadmium 35
• Copper 1,340
• Lead 268
• Mercury 15
• Molybdenum -
• Nickel 375
• Selenium 89
• Zinc 2,500

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In class exercise

• With addition of 200 lb. of available N to a corn
  crop, how much liquid dairy manure is needed.
  How much total P is added? How much K is added?
  Assume pond storage (anaerobic liquid) and
  knifing into the soil. Assume 20handling loss
  of total N. Assume no application losses.

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Answer

• Total N 2.4
• P 0.76
• K 0.75
• N
• 20 loss 0.2 x 2.4 .48
• Remainder is 1.92
• 30 ammonium N 0.3x1.92 0.56
• Organic N 1.92 - .56 1.3
• Available (1.3 x 0.3) 0.56 0.958

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Answer

• 200 lb. of N 200/.0095 21000 lb. of dry
  manure per acre
• K assume 100 available and no losses.
• Quantity of K 21000 x .0075 158 lb/ac
• K2O 158/0.83 190
• P - assume 100 available and no losses.
• Quantity of P 21000 x .0076 160 lb/ac
• P2O5 160/0.44 363

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Summary

• N fertilizers, when added to well drained soils,
  form nitrate.
• Nitrate causes blue baby syndrome.
• Nitrate is very mobile.
• Nitrate contamination of ground waters is a
  common problem.
• Phosphate fertilization can result in P pollution
  of surface waters.

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Summary (cont.)

• For large animal operations (CAFOs) manure
  storage and disposal is a problem.
• Current regulations are such that a manure plan
  in Minnesota requires enough cropland to utilize
  the manure N but this is shifting to include P,
  especially in high soil test P soils.
• Estimation of manure application requires
  knowledge of ammonium N and the availability
  fraction.

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Summary (cont.)

• Other elements of concern in manure are As and Cu

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Daily assignment (1) Mon Oct. 30

• 10,000 gallons of irrigation water containing 40
  ppm nitrate N is applied to an acre. How many
  pounds of of N are added?

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Daily assignment (2) Wed. Nov. 1

• If 5 tons (English) are added to acre how many
  pounds of N and P are added if the analysis
  shows
• N, 3.2
• P, 1.6

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• Water is 8.3 lb/gal
• 83000 lb of water.
• (83000)(4.0 x 10 -5) 3.3 Lb