NUTRIENT LOSSES FROM MANAGEMENT INTENSIVE GRAZING DAIRY FARMS IN CENTRAL MARYLAND

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NUTRIENT LOSSES FROM MANAGEMENT INTENSIVE GRAZING
DAIRY FARMS IN CENTRAL MARYLAND

• Ray R. Weil and Rachel E. Gilker
• Dept. of Natural Resource Sciences and Landscape
  ArchitectureUniversity of Maryland, College Park
• in collaboration with
• Bill Stout
• late, USDA Pasture Lab, PA

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Dairy Farming Changing Feed
Feeding silage
Grazing
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Confined Feeding Systems
Manure on the move

• Grow, harvest and transport crops.
• Import feed and fertilizer
• Collect, store and haul manure

High capital costs

• High production per cow and per acre.
• High cost per CWT milk.

Cows standing still
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Management Intensive Grazing (MIG)

• Farmland covered in perennial grass instead of
  annual crops.
• Little erosion or sediment loss
• Cows managed to harvest feed and spread
  manure.
• Low need for imported feed, fertilizer, fuel.

Grass stands still

• Seasonal milk production
• Modest production per cow
• Much lower cost per CWT
• ? Higher profitability.
• Less control over manure/urine distribution?

Cows harvest feed
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Grazers control manure distribution by managing
cows, water, fencing, etc.
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Grass controls erosionbut does grazing cause
nutrient pollution?

• 70 -85 of N and P ingested passes thru the cow.
• 500-1000 kg N/ha/yr directly under urine and
  fecal patches.
• Excretions by grazing cows cover only about 15
  of pasture surface in any 1 year.

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Nutrient Pollution Research

• Previous research has suggested intensive grazing
  causes high N leaching.
• NZ and European research used high N
  fertilization rates (300 - 600 kgN/ha).
• Monolith lysimeters used in some research may
  cause artifact ponding and preferential flow
  patterns.

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Nutrient Pollution Predictions
Stocking rates on MIG farms in our study
Predicted Mean Annual Ground Water Nitrate-N (ppm)
Cumulative Seasonal Stocking Rates (AUD/ha)
From Stout, W.L., et al. 2000. J. Soil Water
Cons.238-243.
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Artifact ponding and preferential flow?
Urine spots in the field
Relative size of leaching lysimeter
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Objectives were to

• monitor nutrient concentrations in groundwater
  under 4 MIG and 2 confined-feeding watersheds.
• estimate nutrient loading from 1 confined feeding
  and 2 MIG dairy farms.
• calculate whole farm nutrient balances for the 3
  farms.
• determine if organic forms constitute significant
  part of N and P leaching losses.

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Recent studies suggest organic forms may be
important for N and P losses

• Currie et al, 1996 Measured DON at 56 67 of
  total N under pine and hardwood stands. (MA)
• Smolander et al, 2001 DON was 62-83 of total N
  in soil solution under spruce stands. (Norway)
• Streeter et al, 2003 60 of the N in lakes of
  agricultural catchments in organic form (UK)
• Willet et al, 2004 DON makes up 40-50 of total
  N in streams and lakes, and may be 85 of TDN.
  (Wales)

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Hypotheses

• Average groundwater N and P under MIG will be
  those under confined feeding.
• Annual average N and P will be below acceptable
  limits.
• Nitrate-N 10 mg/L
• Dissolved Reactive Phosphate 0.01 mg/L?
• Total P 0.1 mg/L?
• Nutrient surpluses lower on the MIG farms than on
  the confined feeding farm.
• Significant organic N and P in groundwater under
  dairy farms.

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Three Md. Farms in this Study
Profit /CWT 6.99 4.34
3.60
1 AU one animal unit of 454 kg 2 AUD
annual AU days per ha
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Methods

• 3 farms, each with 2 watersheds (A and B).
• A transect of 3 piezometer nests at outlet of
  each watershed ( 1 upslope control well on each
  farm).
• 3 or 4 piezometers in each nest each 1 m deeper
  than the next.
• 5 stations 100 m apart along each of two streams
  on Grazer 2 farm.

A nest of three piezometers
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Groundwater Monitoring Design
Nest C
Nest B
Nest A
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Sampling May 2001-July 2004
Confined A

• Groundwater sampled biweekly.
• Streams on Grazer 2 farm sampled biweekly plus
  storms.

Grazer 2 A
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Nitrate - N and groundwater levels under six
watersheds
05/01 06/04
Water table
Nitrate-N
Because of drought, only data from 10/02 06/04
used for statistical comparisons
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Nitrate-N in groundwater under six watersheds
during the study period
N2700
Distance weighted least squares lines
Drought period (5/01-11/02) excluded
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Annual average nitrate N
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(No Transcript)
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Nitrate-N in three piezometer nests under six
watersheds during the study period
Jan 02 Mar 04
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Groundwater nutrients by proximity of watershed
to barnyard
Nitrate-N
Dissolved Organic P
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Dissolved Organic and Inorganic Nitrogen in
Groundwater under Six Dairy Watersheds
DON 20 of Total N
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Dissolved Organic and Inorganic Phosphorus in
Groundwater under Six Dairy Watersheds
Means of 106 to 160 samples
Org. P varies from 20 to 43 of Total dissolved P
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Stream Water Total Nitrogen
Watershed A
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Stream Water Total Nitrogen
Watershed B
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Streamwater P across grazed watersheds (means of
two streams)
Storm flow
Base flow
Flow direction
Flow direction
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TDN
TDP
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Percent of dissolved N and P in organic forms
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a Vinten, A.J.A. 1999. Predicting water and
chloride transport in drained soils derived from
glacial till. J. Environmental Quality 28980-987.
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Relationship Between Nutrient Input-output
Surplus and Estimated Nitrate-N Leaching Loss for
Three Maryland Dairy Farms.
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Summary for MIG watersheds

• Annual stocking rates were 348-810 animal
  days/ha.
• Monolith lysimeter research (Stout et al., 2000)
  predicted annual average NO3-N of 15 and 32 ppm
  in leachate for these stocking rates.
• We found annual average NO3-N of 4 and 6 ppm in
  shallow groundwater for these stocking rates.

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Summary for MIG groundwater

• Nitrate-N averaged 4.4 mg/L.
• Total dissolved N averaged 5.2 mg/L.
• (of which 20 2 was organic)
• Total dissolved P averaged 0.136 mg/L.
• (of which 32 1 was organic)

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Summary for MIG watersheds

• Stream base-flow N and P levels not affected by
  grazed pastures.
• Storm flow P in one stream was elevated when
  passing winter holding area.
• Nutrient surpluses/ha on grazing farms were lower
  than on confined farm, even if animal units/acre
  were equal.

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Conclusions

• We found N and P leaching under MIG pastures no
  higher than under manured cropland.
• N leaching losses were related to surplus in farm
  nutrient balance.
• MIG appears to have potential as a profitable
  Best Management Practice for environmental
  quality.

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Thanks to the NE SARE program of USDA for
funding, and to the three farmers for their kind
cooperation and good stewardship of the land.