nutrient losses from management intensive grazing dairy farms in central maryland ray r. weil and...
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NUTRIENT LOSSES FROM MANAGEMENT NUTRIENT LOSSES FROM MANAGEMENT INTENSIVE GRAZING DAIRY FARMSINTENSIVE GRAZING DAIRY FARMS
IN CENTRAL MARYLAND IN CENTRAL MARYLAND
NUTRIENT LOSSES FROM MANAGEMENT NUTRIENT LOSSES FROM MANAGEMENT INTENSIVE GRAZING DAIRY FARMSINTENSIVE GRAZING DAIRY FARMS
IN CENTRAL MARYLAND IN CENTRAL MARYLAND
Ray R. WeilRay R. Weil and and Rachel E. GilkerRachel E. Gilker Dept. of Natural Resource Sciences and Landscape Dept. of Natural Resource Sciences and Landscape
ArchitectureArchitectureUniversity of Maryland, College ParkUniversity of Maryland, College Park
in collaboration within collaboration withBill StoutBill Stout
late, USDA Pasture Lab, PA
Dairy Farming: Changing Feed…Dairy Farming: Changing Feed…
……into Milkinto Milk
Feeding Feeding silagesilage
GrazinGrazing g
Confined Feeding SystemsConfined Feeding Systems
High production per cow and per High production per cow and per
acre.acre. High cost per CWT milk. High cost per CWT milk.
Grow, harvest and transport Grow, harvest and transport crops.crops.
Import feed and fertilizerImport feed and fertilizer Collect, store and haul manureCollect, store and haul manure
Cows standing stillCows standing still
Manure on the move Manure on the move
High capital costsHigh capital costs
Farmland covered in perennial Farmland covered in perennial grass instead of annual crops.grass instead of annual crops.Little erosion or sediment Little erosion or sediment
lossloss Cows managed to ‘harvest’ Cows managed to ‘harvest’
feed and ‘spread’ manure. feed and ‘spread’ manure. Low need for imported feed, Low need for imported feed,
fertilizer, fuel.fertilizer, fuel.
Management Intensive Grazing (MIG) Management Intensive Grazing (MIG)
Seasonal milk productionSeasonal milk production Modest production per cowModest production per cow Much lower cost per CWTMuch lower cost per CWT
Higher profitability.Higher profitability. Less control over manure/urine Less control over manure/urine
distribution?distribution?
Grass stands stillGrass stands still
Cows harvest feedCows harvest feed
Grazers control manure distribution by managing cows, water, fencing, etc.
Grass controls erosion…but does grazing Grass controls erosion…but does grazing cause nutrient pollution?cause nutrient pollution?
70 -85% of N and 70 -85% of N and P ingested P ingested passes thru the passes thru the cow.cow.
500-1000 kg 500-1000 kg N/ha/yr directly N/ha/yr directly under urine and under urine and fecal patches. fecal patches.
Excretions by Excretions by grazing cows grazing cows cover only about cover only about 15% of pasture 15% of pasture surface in any 1 surface in any 1 year.year.
Nutrient Pollution Nutrient Pollution ResearchResearch
Previous research has Previous research has suggested intensive grazing suggested intensive grazing causes high N leaching.causes high N leaching.
NZ and European research NZ and European research used high N fertilization rates used high N fertilization rates (300 - 600 kgN/ha).(300 - 600 kgN/ha).
Monolith lysimeters used in Monolith lysimeters used in some research may cause some research may cause artifact ponding and artifact ponding and preferential flow patterns.preferential flow patterns.
Nutrient Pollution PredictionsNutrient Pollution PredictionsNutrient Pollution PredictionsNutrient Pollution Predictions
From: Stout, W.L., et al. 2000. J. Soil Water Cons.:238-243.
Predicted Mean Annual Ground Water
Nitrate-N (ppm)
Predicted Mean Annual Ground Water
Nitrate-N (ppm)
Cumulative Seasonal Stocking Rates (AUD/ha)Cumulative Seasonal Stocking Rates (AUD/ha)
N fertilizer
White clover
N fertilizer
White clover
Stocking rates on Stocking rates on MIG farms in our MIG farms in our
studystudy
Stocking rates on Stocking rates on MIG farms in our MIG farms in our
studystudy
Urine Urine spots in spots in the fieldthe field
Relative Relative size of size of leaching leaching lysimeterlysimeter
Artifact Artifact ponding and ponding and preferential preferential flow?flow?
Objectives were to… Objectives were to…
monitor monitor nutrient concentrationsnutrient concentrations in in groundwater under 4 MIG and 2 confined-groundwater under 4 MIG and 2 confined-feeding watersheds. feeding watersheds.
estimate estimate nutrient loadingnutrient loading from 1 confined from 1 confined feeding and 2 MIG dairy farms.feeding and 2 MIG dairy farms.
calculate whole farm calculate whole farm nutrient balancesnutrient balances for the 3 farms. for the 3 farms.
determine if determine if organic forms organic forms constitute constitute significantsignificant part ofpart of N and P N and P leaching leaching losses.losses.
Recent studies suggest Recent studies suggest organic forms may be organic forms may be important for N and P losses…important for N and P losses… Currie et al, 1996: Measured DON at 56 & 67% of Currie et al, 1996: Measured DON at 56 & 67% of
total N under pine and hardwood stands. total N under pine and hardwood stands. (MA)(MA)
Smolander et al, 2001: DON was 62-83% of total Smolander et al, 2001: DON was 62-83% of total N in soil solution under spruce stands. N in soil solution under spruce stands. (Norway)(Norway)
Streeter et al, 2003: Streeter et al, 2003: 60% of the N in lakes of agricultural catchments in organic form (UK) (UK)
Willet et al, 2004: DON makes up 40-50% of total Willet et al, 2004: DON makes up 40-50% of total N in streams and lakes, and may be >85% of N in streams and lakes, and may be >85% of TDN. TDN. (Wales)(Wales)
HypothesesHypotheses Average groundwater N and P under MIG will be Average groundwater N and P under MIG will be
≤≤ those under confined feeding.those under confined feeding. Annual average N and P will be below acceptable Annual average N and P will be below acceptable
limits.limits.Nitrate-N: 10 mg/LNitrate-N: 10 mg/L
Dissolved Reactive Phosphate: 0.01 mg/L?Dissolved Reactive Phosphate: 0.01 mg/L?Total P: 0.1 mg/L?Total P: 0.1 mg/L?
Nutrient surpluses lower on the MIG farms than Nutrient surpluses lower on the MIG farms than on the confined feeding farm.on the confined feeding farm.
Significant Significant organicorganic N and P in groundwater under N and P in groundwater under dairy farms.dairy farms.
Three Md. Farms in this Study Three Md. Farms in this Study
9.97.81.5P
1737154NSurplus kg/ha
23 t ha-1 y-1810348AUD2 orManure
6 yr: corn/oats/alfalfa
pasture/ 24% legume
pasture/ 8% legume
Vegetation
2.12.20.95AU1/ha
2457183Farm, ha
ConfinedGrazer2Grazer1
1 AU = one animal unit of 454 kg 2 AUD = annual AU days per ha
Profit: $/CWT: 6.99 4.34 3.60
Methods…Methods… 3 farms, each with 2 3 farms, each with 2
watersheds (A and B).watersheds (A and B). A transect of 3 piezometer A transect of 3 piezometer
nests at outlet of each nests at outlet of each watershed (+ 1 upslope watershed (+ 1 upslope control well on each farm).control well on each farm).
3 or 4 piezometers in each 3 or 4 piezometers in each nest – each 1 m deeper nest – each 1 m deeper than the next.than the next.
5 stations 100 m apart 5 stations 100 m apart along each of two streams along each of two streams on Grazer 2 farm.on Grazer 2 farm.
A nest of three piezometers
Groundwater Monitoring Groundwater Monitoring DesignDesign
Nest ANest ANest BNest B
Nest CNest C
1- 6 ha watershed1- 6 ha watershed
CCCCBBBB
AAAA
Sampling Sampling May 2001-July 2004May 2001-July 2004
Groundwater Groundwater sampled biweekly.sampled biweekly.
Streams on Grazer 2 Streams on Grazer 2 farm sampled farm sampled biweekly + plus biweekly + plus storms.storms.
Confined AConfined A
Grazer 2 AGrazer 2 A
0
10
20
30
40
Nitr
ate-
N,
mg
L-1
0
10
20
30
40
Nitr
ate-
N,
mg
L-1
Nitrate-NWater table
500600
700800
9001000
1100
12001300
14001500
16001700
Day of Century
0
10
20
30
40
Nitr
ate-
N,
mg
L-1
0
10
20
30
40
Nitr
ate-
N,
mg
L-1
0
10
20
30
40
Nitr
ate-
N,
mg
L-1
Nitrate-NWater table
500600
700800
9001000
1100
12001300
14001500
16001700
Day of Century
0
10
20
30
40
Nitr
ate-
N,
mg
L-1
500600
700800
9001000
1100
12001300
14001500
16001700
Day of Century
Grazer 1 A
Soil surface
EPA limit
Grazer 1 B
Grazer 2 A Grazer 2 B
Confined A Confined B
Nitrate - NNitrate - N and
groundwater levels
under six watersheds
Nitrate - NNitrate - N and
groundwater levels
under six watersheds05/01 – 06/0405/01 – 06/04
Water tableWater table
Nitrate-NNitrate-N
Because of drought, only data from 10/02 – 06/04 used for statistical comparisons
Because of drought, only data from 10/02 – 06/04 used for statistical comparisons
Nitrate-N Nitrate-N in groundwater under six watersheds during the study period
1000 1100 1200 1300 1400 1500 1600 1700Day of Century
0
10
20
30
40
50N
i tra t
e N
, m
g/L
Grazer 2Grazer 1Confined
1000 1100 1200 1300 1400 1500 1600 1700Day of Century
0
10
20
30
40
50N
i tra t
e N
, m
g/L
Grazer 2Grazer 1Confined
Drought period
(5/01-11/02) excluded
Drought period
(5/01-11/02) excluded
2003 20042002
1000 1100 1200 1300 1400 1500 1600 1700Day of Century
0
10
20
30
40
50N
i tra t
e N
, m
g/L
Grazer 2Grazer 1Confined
Grazer 2Grazer 1Confined
1000 1100 1200 1300 1400 1500 1600 1700Day of Century
0
10
20
30
40
50N
i tra t
e N
, m
g/L
Grazer 2Grazer 1Confined
Grazer 2Grazer 1Confined
Distance weighted least squares lines
Distance weighted least squares lines
N=2700
0
5
10
15
20
25
30
35
40N
itrat e
- N, m
g L
-1
Spring Summer Fall WinterSEASON
0
5
10
15
20
25
30
35
40
Nitr
at e
- N, m
g L
-1
Grazer 2Grazer 1Confined
0
5
10
15
20
25
30
35
40N
itrat e
- N, m
g L
-1
Spring Summer Fall WinterSEASON
0
5
10
15
20
25
30
35
40
Nitr
at e
- N, m
g L
-1
Grazer 2Grazer 1Confined
Annual Annual average average
nitrate –Nnitrate –N
Annual Annual average average
nitrate –Nnitrate –N
20022002
20032003 95%confidenceInterval formean
Box plot
1000 1100 1200 1300 1400 1500 1600 1700Day of Century
0
10
20
30
40
50To
tal D
isso
l ve
d N
, mg
/ L
Grazer 2Grazer 1Confined
2002 <------------ 2003 ---------------> <------- 2004 ------>
Groundwater TDNMeans of 2 watershedson each farm
1000 1100 1200 1300 1400 1500 1600 1700Day of Century
0
10
20
30
40
50To
tal D
isso
l ve
d N
, mg
/ L
Grazer 2Grazer 1Confined
2002 <------------ 2003 ---------------> <------- 2004 ------>
Groundwater TDNMeans of 2 watershedson each farm
Jan 02 – Mar 04
Jan 02 – Mar 04
Nitrate-NNitrate-N in in three three
piezometer piezometer nestsnests under
six watersheds during the
study period
0
10
20
30
40
Nitr
ate-
N, m
g L
-1
0
10
20
30
40
Nitr
ate-
N, m
g L
-1
ctrlcba
Nest
700800
9001000
1100
12001300
14001500
Day of Century
0
10
20
30
40
Nitr
ate-
N, m
g L
-1
700800
9001000
1100
12001300
14001500
Day of Century
Grazer 1 A Grazer 1 B
Grazer 2 A Grazer 2 B
Confined A Confined B
0
10
20
30
40
Nitr
ate-
N, m
g L
-1
0
10
20
30
40
Nitr
ate-
N, m
g L
-1
ctrlcba
Nest
700800
9001000
1100
12001300
14001500
Day of Century
0
10
20
30
40
Nitr
ate-
N, m
g L
-1
700800
9001000
1100
12001300
14001500
Day of Century
Grazer 1 A Grazer 1 B
Grazer 2 A Grazer 2 B
Confined A Confined B
Nest aNest aNest bNest b
Nest cNest c
Confined Grazer 1 Grazer 20
3
6
9
12
Nitr
ate
-N,
mg
/L
homesteadaway
Confined Grazer 1 Grazer 20
3
6
9
12
Nitr
ate
-N,
mg
/L
homesteadaway
Confined Grazer 1 Grazer 20.01
0.02
0.03
0.04
0.05
Dis
solv
ed
Org
an
ic P
, mg
/ L
homesteadaway
Confined Grazer 1 Grazer 20.01
0.02
0.03
0.04
0.05
Dis
solv
ed
Org
an
ic P
, mg
/ L
homesteadaway
Nitrate-NNitrate-N Dissolved Organic PDissolved Organic P
Groundwater nutrients by proximity of watershed to barnyard
0
5
10
15
N in
gro
un
dw
ate
r, m
g/ L
DONNO3-N
2002-2003
0
5
10
15
N in
gro
un
dw
ate
r, m
g/ L
DONNO3-N
2002-2003
Dissolved Organic and Inorganic Nitrogen in Groundwater under Six Dairy Watersheds
DON = 20% of Total NDON = 20% of Total N
0.00
0.05
0.10
0.15
0.20
0.25
0.30
Dis
so
lve
d P
, m
g/L Diss Organic P
Diss Reactive P
Dissolved Organic and Inorganic Phosphorus in Groundwater under Six Dairy Watersheds
Org. P varies from 20 to 43% of Total dissolved P
Org. P varies from 20 to 43% of Total dissolved P
Grazer 2 Grazer 2 farm farm located on located on calcareous calcareous parent parent material.material.
Grazer 2 Grazer 2 farm farm located on located on calcareous calcareous parent parent material.material.
Means of 106 to 160 samples
Means of 106 to 160 samples
Stream Water Total NitrogenStream Water Total NitrogenWatershed AWatershed A
1 2 3 4 5SITE
0
1
2
3
4
5
Str
eam
wat
er N
, ppm
DONNO3-N
05/01 - 02/04Storm flow, stream A
Storm FlowStorm Flow
Stream Flow
1 2 3 4 5SITE
0
1
2
3
4
5
Str
ea
m w
ate
r N
, p
pm DON
NO3-N05/01 - 02/04Base flow, stream A
Base FlowBase Flow
Stream Flow
Stream Water Total NitrogenStream Water Total NitrogenWatershed BWatershed B
1 2 3 4 5SITE
0
1
2
3
4
5
Str
eam
wat
er N
, pp
m DONNO3-N
05/01 - 02/04Base flow, stream B
Base FlowBase Flow
Stream Flow
1 2 3 4 5SITE
0
1
2
3
4
5
Str
ea
m w
ate
r N
, pp
m DONNO3-N
05/01 - 02/04Storm flow, stream B
Storm FlowStorm Flow
Stream Flow
1 2 3 4 5CTRL
Sampling station
0.00
0.05
0.10
0.15
0.20
P c
onc.
(m
g /L )
1 2 3 4 5CTRL
Sampling station
Particulate PDiss. Org PDiss. Reactive P
Storm flow8 dates
Base flow23 dates
Storm flowStorm flow Base flowBase flow
Streamwater P across grazed watersheds (means of two
streams)
Flow directionFlow direction Flow directionFlow direction
1 2 3 4 5Sampling site
0.00
0.05
0.10
0.15
0.20
0.25
Tota
l Dis
slo
ved
Ph
osp
ho
rus,
mg
/L
Stream 2, storm flowStream 2, base flowStream 1, storm flowStream 1, base flow
1 2 3 4 5Sampling site
0.00
0.05
0.10
0.15
0.20
0.25
Tota
l Dis
slo
ved
Ph
osp
ho
rus,
mg
/L
Stream 2, storm flowStream 2, base flowStream 1, storm flowStream 1, base flow
1 2 3 4 5Sampling site
0
1
2
3
4
5
Tota
l Dis
s lov
ed N
itrog
en,
mg/
L
Stream 2, storm flowStream 2, base flowStream 1, storm flowStream 1, base flow
1 2 3 4 5Sampling site
0
1
2
3
4
5
Tota
l Dis
s lov
ed N
itrog
en,
mg/
L
Stream 2, storm flowStream 2, base flowStream 1, storm flowStream 1, base flow
Stream Flow Stream Flow
TDNTDNTDPTDP
0
10
20
30
40
50D
issolv
ed n
utr
ient in
org
anic
form
, %
PN
Nutrient
0
10
20
30
40
50D
issolv
ed n
utr
ient in
org
anic
form
, %
PN
Nutrient
Percent of dissolved N and P in organic formsPercent of dissolved N and P in organic forms
Mean annual nutrient losses in groundwater for three dairy farms in Maryland Based on drainage
volumes estimated using WATBALa.
FarmFarm Nitrate-NNitrate-N TDNTDN DRPDRP TDPTDP
------------------ kg ha-1 y-1
----------
Confined feeding farm
24 30 0.50 0.60
MIG Grazer 1 12 14 0.55 0.62
MIG Grazer 2 16 20 0.11 0.26
a Vinten, A.J.A. 1999. Predicting water and chloride transport in drained soils derived from glacial till. J. Environmental Quality 28:980-987.
Relationship Between Nutrient Input-output Surplus and
Estimated Nitrate-N Leaching Loss for Three Maryland Dairy
Farms.
0 25 50 75 100 125 150 175 200
N Surplus (kg ha-1 y-1 )
5
10
15
20
25
30
Nitr
ate
-N lo
ss (
k g h
a- 1 y
- 1)
Confined
Grazed2
Grazed1
2Y = 7.7+0.11*XR =0.91**
Summary for MIG watershedsSummary 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 ppm15 and 32 ppm in leachate for these stocking rates.
We found annual average NO3-N of 4 4
and 6 ppmand 6 ppm in shallow groundwater for these stocking rates.
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 ppm15 and 32 ppm in leachate for these stocking rates.
We found annual average NO3-N of 4 4
and 6 ppmand 6 ppm in shallow groundwater for these stocking rates.
1.1. Nitrate-N Nitrate-N averaged averaged 4.4 mg/L.4.4 mg/L.
2.2. Total dissolved N averaged 5.2 Total dissolved N averaged 5.2 mg/L.mg/L.
(of which 20 (of which 20 ± 2± 2% was organic)% was organic)
Total dissolved P averaged Total dissolved P averaged 0.136 mg/L.0.136 mg/L.
(of which 32 (of which 32 ± 1± 1 % was organic) % was organic)
1.1. Nitrate-N Nitrate-N averaged averaged 4.4 mg/L.4.4 mg/L.
2.2. Total dissolved N averaged 5.2 Total dissolved N averaged 5.2 mg/L.mg/L.
(of which 20 (of which 20 ± 2± 2% was organic)% was organic)
Total dissolved P averaged Total dissolved P averaged 0.136 mg/L.0.136 mg/L.
(of which 32 (of which 32 ± 1± 1 % was organic) % was organic)
Summary for MIG Summary for MIG groundwatergroundwater
4. Stream base-flow N and P levels not affected by grazed pastures.
5. Storm flow P in one stream was elevated when passing winter holding area.
6. Nutrient surpluses/ha on grazing farms were lower than on confined farm, even if animal units/acre were equal.
4. Stream base-flow N and P levels not affected by grazed pastures.
5. Storm flow P in one stream was elevated when passing winter holding area.
6. Nutrient surpluses/ha on grazing farms were lower than on confined farm, even if animal units/acre were equal.
Summary for MIG Summary for MIG watershedswatersheds
ConclusionsConclusions
We found N and P leaching under MIG pastures We found N and P leaching under MIG pastures no higher than under manured cropland.no higher than under manured cropland.
N leaching losses were related to surplus in N leaching losses were related to surplus in farm nutrient balance.farm nutrient balance.
MIG appears to have potential as a profitable MIG appears to have potential as a profitable Best Management Practice for environmental Best Management Practice for environmental quality.quality.
Thanks to the NE SARE program of Thanks to the NE SARE program of USDA for funding, and to the three USDA for funding, and to the three farmers for their kind cooperation farmers for their kind cooperation and good stewardship of the land.and good stewardship of the land.