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 Architecture University of Maryland, College Park in collaboration with Bill Stout late, USDA Pasture Lab, PA

Dairy Farming: Changing Feed… …into Milk Feeding silage Grazing

Confined Feeding Systems  High production per cow and per acre.  High cost per CWT milk. Grow, harvest and transport crops. Grow, harvest and transport crops. Import feed and fertilizer Import feed and fertilizer Collect, store and haul manure Collect, store and haul manure Cows standing still Manure on the move High capital costs

Farmland covered in perennial grass instead of annual crops. Farmland covered in perennial grass instead of annual crops. Little erosion or sediment loss Cows managed to ‘harvest’ feed and ‘spread’ manure. Cows managed to ‘harvest’ feed and ‘spread’ manure. Low need for imported feed, fertilizer, fuel. Low need for imported feed, fertilizer, fuel. Management Intensive Grazing (MIG)  Seasonal milk production  Modest production per cow  Much lower cost per CWT  Higher profitability.  Less control over manure/urine distribution? Grass stands still Cows harvest feed

Grazers control manure distribution by managing cows, water, fencing, etc.

Grass controls erosion…but does grazing cause nutrient pollution? % of N and P ingested passes thru the cow % of N and P ingested passes thru the cow kg N/ha/yr directly under urine and fecal patches 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. Excretions by grazing cows cover only about 15% of pasture surface in any 1 year.

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

Nutrient Pollution Predictions From: Stout, W.L., et al J. Soil Water Cons.: Predicted Mean Annual Ground Water Nitrate-N ( ppm ) Cumulative Seasonal Stocking Rates (AUD/ha) N fertilizer White clover N fertilizer White clover Stocking rates on MIG farms in our study

Urine spots in the field Relative size of leaching lysimeter Artifact ponding and preferential flow?

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

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) 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) Smolander et al, 2001: DON was 62-83% of total N in soil solution under spruce stands. (Norway) Streeter et al, 2003: (UK) 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) Willet et al, 2004: DON makes up 40-50% of total N in streams and lakes, and may be >85% of TDN. (Wales)

Hypotheses Average groundwater N and P under MIG will be ≤ those under confined feeding. Average groundwater N and P under MIG will be ≤ those under confined feeding. Annual average N and P will be below acceptable limits. 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. Nutrient surpluses lower on the MIG farms than on the confined feeding farm. Significant organic N and P in groundwater under dairy farms. Significant organic N and P in groundwater under dairy farms.

Three Md. Farms in this Study P NSurplus kg/ha 23 t ha -1 y AUD 2 or Manure 6 yr: corn/oats/ alfalfa pasture/ 24% legume pasture/ 8% legume Vegetation AU 1 /ha Farm, ha ConfinedGrazer2Grazer1 1 AU = one animal unit of 454 kg 2 AUD = annual AU days per ha Profit: $/CWT:

Methods… 3 farms, each with 2 watersheds (A and B). 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). 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. 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. 5 stations 100 m apart along each of two streams on Grazer 2 farm. A nest of three piezometers

Groundwater Monitoring Design Nest A Nest B Nest C 1- 6 ha watershed CC BB AA

Sampling May 2001-July 2004 Groundwater sampled biweekly. Groundwater sampled biweekly. Streams on Grazer 2 farm sampled biweekly + plus storms. Streams on Grazer 2 farm sampled biweekly + plus storms. Confined A Grazer 2 A

Nitrate - N 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

Nitrate-N Nitrate-N in groundwater under six watersheds during the study period Drought period (5/01-11/02) excluded Distance weighted least squares lines N=2700

Annual average nitrate –N % confidence Interval for mean Box plot

Jan 02 – Mar 04 Nitrate-N in three piezometer nests Nitrate-N in three piezometer nests under six watersheds during the study period Nest a Nest b Nest c

Nitrate-N Dissolved Organic P Groundwater nutrients by proximity of watershed to barnyard

Dissolved Organic and Inorganic Nitrogen in Groundwater under Six Dairy Watersheds DON = 20% of Total N

Dissolved Organic and Inorganic Phosphorus in Groundwater under Six Dairy Watersheds Org. P varies from 20 to 43% of Total dissolved P Grazer 2 farm located on calcareous parent material. Means of 106 to 160 samples

Stream Water Total Nitrogen Watershed A Storm Flow Stream Flow Base Flow Stream Flow

Stream Water Total Nitrogen Watershed B Base Flow Stream Flow Storm Flow Stream Flow

Storm flow Base flow Streamwater P across grazed watersheds (means of two streams) Flow direction

Stream Flow TDN TDP

Percent 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 WATBAL a. FarmNitrate-NTDNDRPTDP kg ha -1 y Confined feeding farm MIG Grazer MIG Grazer a Vinten, A.J.A Predicting water and chloride transport in drained soils derived from glacial till. J. Environmental Quality 28:

Relationship Between Nutrient Input-output Surplus and Estimated Nitrate-N Leaching Loss for Three Maryland Dairy Farms.

Summary for MIG watersheds Annual stocking rates were animal days/ha. 15 and 32 ppm Monolith lysimeter research (Stout et al., 2000) predicted annual average NO 3 -N of 15 and 32 ppm in leachate for these stocking rates. 4 and 6 ppm We found annual average NO 3 -N of 4 and 6 ppm in shallow groundwater for these stocking rates. Annual stocking rates were animal days/ha. 15 and 32 ppm Monolith lysimeter research (Stout et al., 2000) predicted annual average NO 3 -N of 15 and 32 ppm in leachate for these stocking rates. 4 and 6 ppm We found annual average NO 3 -N of 4 and 6 ppm in shallow groundwater for these stocking rates.

1. Nitrate-N averaged 4.4 mg/L. 2. Total dissolved N averaged 5.2 mg/L. (of which 20 ± 2% was organic) Total dissolved P averaged mg/L. Total dissolved P averaged mg/L. (of which 32 ± 1 % was organic) 1. Nitrate-N averaged 4.4 mg/L. 2. Total dissolved N averaged 5.2 mg/L. (of which 20 ± 2% was organic) Total dissolved P averaged mg/L. Total dissolved P averaged mg/L. (of which 32 ± 1 % was organic) Summary for MIG groundwater

4. 4. 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 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. Summary for MIG watersheds

Conclusions We found N and P leaching under MIG pastures no higher than under manured cropland. 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. 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. MIG appears to have potential as a profitable Best Management Practice for environmental quality.

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.