Improved efficiency of grazing dairies using complementary pasture species and irrigation scheduling

Improved efficiency of grazing dairies using complementary pasture species and irrigation scheduling

Summary

Yield, growth rates, and persistence of forage species were determined for each month of the year at two geographically distinct locations in the Coastal Plain of Georgia. No cool season perennial species tolerated the southern location, but several perennial cool season grasses and one perennial legume survived at the northern location. November is a challenging month as no forage species were productive during this critical period. Nitrogen budgeting on the farm showed little nitrate leaching or ammonia volatilization. Two field days attracted 85 and 140 dairymen or industry representatives interested in developing or converting conventional confined dairies to grazing dairies.

Objectives/Performance Targets

1. Screen warm and cool-season annual and perennial pasture species for seasonal forage productivity under grazing conditions, 2. Determine moisture release curves for the major soil types found on cooperating grazing dairies and monitor soil moisture content from irrigation practices during periods of negative water balance, 3. Create a nitrogen “budget” to determine precisely when, and by how much, the dairies are deficient in nitrogen supply from pasture legumes, 4. Develop educational and outreach information for training producers to be more efficient at, or transition into, pasture-based dairying.

Accomplishments/Milestones

We now have two nearly complete years of forage production data to indicate which species are adapted to management intensive rotational grazing systems common to the dairy farms on which we are conducting research. The only pasture legume which persisted in our trials was white clover which persisted at the northern Coastal Plain location only. Cool season grasses were tested because of superior forage quality. None persisted in the southern coastal plain. Several tall fescue cultivars, including soft leaf types, and one perennial ryegrass expressed persistence at the northern coastal plain location. Cool season annual grasses had greater yield and better forage quality than the perennial cool season grasses. Tifton 85 bermudagrass was superior in yield and quality compared to Coastcross II and Tifquick bahiagrass. Forage production was limited during the month of November.

Soil moisture sensors were used to monitor irrigation needs and scheduling on a “managed” center pivot and a “control” center pivot. Producers have access to the data on the managed pivot, but not the control pivot. This provides us with an opportunity to guage how well producers are predicting their irrigation needs. Comparison of the soil moisture data between the two pivot systems suggests producers are doing a good job of scheduling irrigation events to meet the forage needs. Ground water accumulates only occurs as a result of heavy rainfall events, but producers generally use irrigation to maintain soil moisture between 40 and 90% of field capacity. Nitrogen imported into the system as fertilizer or in feed was calculated. Nitrogen export from milk and hay, N in standing forage, and N losses by ammonia volatilization and nitrate leaching were measured. Most of the N in the system was present in the standing forage. Nitrogen use efficiency was calculated as the percentage losses (ammonia and nitrate) compared to the total N imported on the farm. The N use efficiency was very high – 78% on one farm and 89% on the other.

Two meetings were conducted in which the strategy of the grazing dairy was compared to the conventional confinement dairy. Data was presented from our research program to illustrate the environmental benefits as well as production limitations for the grazing dairy model. Site visits to grazing dairies were included at which the dairymen expressed their experiences and insight into the system. Eighty people registered at one meeting and 140 at the other meeting. Data was received with some skepticism from conventional dairymen, but the majority of the discussion focused on grazing dairy start-ups or conversion from conventional to grazing dairies.

Impacts and Contributions/Outcomes

The potential for nutrient loading and environmental pollution from conventional dairies is a sensitive issue. The fact that N use efficiency on grazing dairies is high indicates that other nutrients (phosphorus) are not likely to be loading the grazing dairy ecosystem. The economic efficiency of the grazing dairy model (as reported by others), the reduced labor input and improved lifestyle for the grazing dairy farmer, combined with the environmental sustainability (reported herein) is attracting attention to producers who are trying to maintain a sustainable family farm.

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