Environmental - Economic Impacts of Management-Intensive Grazing on Dairy Farms

Environmental - Economic Impacts of Management-Intensive Grazing on Dairy Farms

Summary

We are monitoring environmental and economic performance of three central Maryland dairy farms, two using management intensive grazing and one using confined feeding. Using piezometer wells and stream sampling we will monitor nutrient leaching losses from six small watersheds, two on each of the farms. Water analyses and nutrient input/output accounting will be used to help determine the suitability of management-intensive grazing as a best management practice. To date, 57 piezometers and 36 lysimeters have been installed, and water sampling has begun. Laboratory analyses are currently being conducted to determine which forms of nitrogen and phosphorous need to be monitored.

Objectives/Performance Targets

1. Maryland and Pennsylvania nutrient management regulators that learned about the environmental and economic impacts of grazing from this project will promote grazing under certain conditions as a sustainable agricultural practice that will contribute to their state’s nutrient management goals.
   Forty of the confined-feeding dairy farmers in Maryland and Pennsylvania who learned about the environmental and economic impacts of grazing from this project will take steps to switch to grazing.

Accomplishments/Milestones

1. Two small (2-10 ha) watersheds were identified on each of the three farms, and transects were defined for well and lysimeter installations. Along each transect, three nests of three wells each were installed inside protective boxes. Additionally, one control well site was installed on each farm, for a total of 57 wells installed in the six watersheds. To enable sampling of soil pore water, a 90-cm and a 120-cm long suction lysimeter were installed from within each nest, at a 45-degree angle to the surface of the soil, with the tips extending into the pasture or field outside the nest at 60 and 90-cm. The wells within each nest were screened to cover a 3 m range of depths to allow for the collection of the upper meter of groundwater over the leaching season (November to May). Samples have been taken to determine the most appropriate method of sampling, including the number of times a well should be emptied by bailing and time to be allowed for the wells to refill. Based on the minimal change in pH in wells that had been emptied one, two or three times, it was determined that emptying each well a single time before sampling would be sufficient. Two sets of samples were also taken to compare storage methods. One set of samples was frozen between sampling and lab work, while one was stored at 4°C. The results of this comparison should indicate whether any cell lysing caused by freezing might lead to higher levels of organic nitrogen in frozen samples.
   Lab measurements of EC and pH are being conducted for initial water samples. Several sets of samples (270 total) have been sent to the Water Quality Lab at Wye, Md. for analysis of nitrate and anion contents. Phosphorous is to be determined for a representative subset, using ion chromatography. Due to the high input of manure in both the grazing and confined-feed systems, nitrogen and phosphorous may be present in organic as well as inorganic forms. We are therefore investigating methods for measurement of total and organic nitrogen and phosphorous, including alkaline persulfate digestion in pressurized microwave-irradiated chambers.
   Business summaries for the three farms were obtained and will be updated over the course of the project to assist in evaluating the economic performance of the farms.
   As part of the effort to monitor nutrient inputs and outputs, kits for the measurement of milk urea nitrogen were distributed to the three farmers, and the first of 12 monthly measurements was made. The results from these tests, along with nutrient import and export data will show the levels of losses from each farm. Additionally, the levels of milk urea nitrogen can be used to predict nutrient levels in the cows’ excreta, assisting in the determination of levels being applied in the pastures on grazing farms.

Collaborators: