Grass controls erosion…but does grazing cause nutrient pollution?  % of N and P ingested passes thru the cow.  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.  MIG allows:  Seasonal milk production  Modest production/cow  Much lower cost per CWT  Higher profitability.  But less control over manure & urine distribution? Bailing samples from Confined A watershed piezometers. Farmland covered in perennial grass instead of annual crops. Farmland covered in perennial grass instead of annual crops. Little erosion or sediment loss 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) Grass stands still Cows harvest feed, “haul” manure 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. Use results to inform regulators about suitability of MIG as environmental Best Management Practice. The Three Project Farms at a Glance P NSurplus lb/acre 21 T/acre/y351 (810)167 (348)AUD 2 or Manure 6 yr: corn/oats/ alfalfa pasture/ 24% legume pasture/ 8% legume Vegetation in study watersheds 110.5AU 1 /acre Farm, acres ConfinedGrazer2Grazer1 1 AU = one animal unit of 1000lbs 2 AUD = annual AU days per acre, days of grazing by milk cow herd. Does not include heifers or calves. Assumes cows graze 365 days year-1. Profit: $/CWT: Research Approach: Studied 2 grazing and 1 confined feeding dairy farm, 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 3.2 ft deeper than the next. 5 stations 110 yards apart along each of two streams on Grazer 2 farm. Nutrient balance and economic analysis of the 3 farms. A nest of three piezometers on Grazer 2 watershed B Nutrient Pollution Predictions Predicted Mean Annual Ground Water Nitrate-N (ppm) Cumulative Seasonal Stocking Rates (AD/ha) N fertilizer White clover N fertilizer White clover From: Stout, W.L., et al J. Soil Water Cons.: 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 Capital intensive confined feeding facility Sample collection Upper 1 m of groundwater sampled biweekly. Streams on Grazer 2 farm sampled biweekly + plus storms.Streams on Grazer 2 farm sampled biweekly + plus storms. Groundwater Monitoring Design Nest A Nest B Nest C acre watershed C B A 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 Sample analysis Filtered (0.25 micron) to separate particulate form dissolved nutrients. Dissolved nitrate, ammonium and phosphate determined. Pressurized microwave persulfate digestion used for total dissolved N and P. Total N – NO 3 -N + NH 4 -N = dissolved organic N (DON) Total dissolved P - reactive dissolved P = dissolved organic P (DOP) Using nests of monitoring wells (piezometers) set to different depths allowed us to sample the upper 3 ft of groundwater even as the water table fell from winter highs to summer lows. Nitrate-N Dissolved Organic P Groundwater nutrients by proximity of watershed to barnyard Dissolved Organic and Inorganic Nutrients in Groundwater DON = 20% of Total N Org. P varies from 20 to 43% of Total dissolved P Note: Grazer 2 underlain by calcareous rocks that trap P Means of 106 to 160 samples We found N and P leaching under MIG pastures no higher or lower than under manured cropland on confined dairy. Stream water N and P did not increase as base flow crossed MIG pastures, but cattle camping area near one stream increased particulate P during storms. We found no reason reject MIG as an environmental Best Management Practice. We found N and P leaching under MIG pastures no higher or lower than under manured cropland on confined dairy. Stream water N and P did not increase as base flow crossed MIG pastures, but cattle camping area near one stream increased particulate P during storms. We found no reason reject MIG as an environmental Best Management Practice. Conclusions We found annual average NO 3 -N of 4 and 6 ppm in shallow groundwater for annual stocking rates of animal days/ha – far lower that the 15 and 32 ppm predicted by monolith lysimeter research (Stout et al., 2000) for these stocking rates. Stream Water Total Nitrogen Stream Flow Base Flow Stream Flow No increase in N as stream flows through pasture Storm Flow Stream water P across grazed watersheds (means of two streams) Storm flow Base flow Flow direction Water table Nitrate-N Because of drought, only data from 10/02 – 06/04 used for statistical comparisons Nitrate - N Nitrate - N and groundwater levels under six watersheds, 05/01 – 06/04 Intensive Grazing: A Threat to Water Quality? -Ray Weil, Rachel Gilker (Univ. of Md) & Bill Stout (USDA) Mid-Atlantic regulators were concerned about groundwater pollution from MIG as previous research had suggested intensive grazing causes high N leaching. NZ and European research used high N fertilization rates ( lb N/acre). Monolith lysimeters used in some research may cause artifact ponding and preferential flow patterns because simulated urine was confined to lysimeter ring. Installing monolith lysimeters like those used for pasture leaching research in PA. Earlier research may have been flawed by potential for causing rapid leaching by preferential flow down worm channels and soil cracks. This occurs because of momentary ponding when simulated urine is confined by a lysimeter covering a much smaller area than natural urine spots. Urine spots in the field Artifact ponding and preferential flow? Relative size of leaching lysimeter Concern about nutrient pollution from MIG

Watershed A Storm flow Base flow Stream water P across grazed watersheds (means of 2 streams) Flow direction