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

A farm-gate nitrogen balance was conducted on two pasture-based dairy farms to assess atmospheric and ground-water pollution potential. Nitrate losses in water were minimal but volatile N losses were as much as 30% of the fertilizer N. Use of pasture legumes to mitigate use of N fertilizer appears to be marginal they were persistent for only 18 months under intensive grazing regimes. Winter annuals grasses complement warm season perennial species, but cool season perennials were not persistent in the Coastal Plain. Results are being assimilated into extension materials for pasture-based dairies, whose numbers are growing exponentially.

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

1) Alfalfa, red clover, white clover, bermudagrass, bahiagrass, tall fescue, perennial ryegrass, annual ryegrass, cereal rye, oats, and triticale have been tested for productivity under grazing conditions. None of the legumes or cool season perennial grasses tested expressed persistence at either of 2 locations where tested. Tifton-85 bermudagrass had higher yield and quality than other bermudagrass or bahiagrass cultivars. Cereal rye and annual ryegrass complemented one another better than other cool season annual grasses tested.
2) Producers failed to use soil moisture data to adjust irrigation practices despite a friendly computer output with a farm map detailing soil moisture content.
3) Nitrogen volatilization varied depending upon the form of N fertilizer used. Most of the volatile N was ammonia. Thirty percent of applied N was lost as ammonia when dry urea was applied to the pastures, compared to approximately 4% when applied as urea ammonia nitrate through the irrigation system. Very little N was lost as nitrate leaching regardless of form of N applied.
4) Educational/outreach programs involving field days, grazing schools, and systems planning were implemented based upon data from our research.

Impacts and Contributions/Outcomes

The number of cows on pasture-based dairies in Georgia is growing exponentially despite a decrease in the total dairy herd.

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