Forage and Livestock
Dairy Cattle
Seasonal climate variability impacts dairy operations in the Southeast United States. SECC investigators are currently investigating ways to quantify impacts on:
- Milk production due to heat stress (warm and humid seasons decrease milk production)
- Reproduction efficiency due to heat stress (cold and dry seasons enhance fertility)
- Cost of cooling confined facilities (hot seasons require costly cooling systems)
- Selection and production of forage systems
- Nitrogen leaching to ground water (El Niño years have higher risk of N leaching than La Niña years)
Nitrogen Leaching, Dairy Farms, and Seasonal Climate Forecast
| Management | ENSO Phase | ||
|---|---|---|---|
| El Niño | Neutral | La Niña | |
| Amount N Leaching | Highest | Medium | Lowest |
| Environmental Risk | High | High | Medium |
| Plant Biomass Production | Lowest | Medium | Highest |
| Winter Season | Not Fallow | Not Fallow | Could be fallow |
| Optimal Winter Crop | Mix: Oats, Rye, Ryegrass, Wheat | Any | Any |
| Optimal Summer Crop | Bermudagrass, Bahiagrass, Corn | Bermudagrass, Bahiagrass, Corn, Sorghum, Millet | Any |
| Optimal Fall Crop | Any | Any | Corn, Sorghum, Millet |
| Waste System | Collect all solids, export manure, make compost, reduce manure N application | Collect solids, plan applications, plan grazing | Normal Operations |
| Herd Management | Plan higher pregnancy for late winter, decrease number of animals, decrease protein in diet, allow more grazing | Decrease protein in diet, reduce confined time | Normal Operations |
The results above come from the integration of models that whole-dairy-farms in north Florida. Estimations of N leaching consistently are highest during El Niño years and lowest during La Niña years. Great inter-phase variability is noticed directly related to the occurrence and intensity of rainfall events. Dairy farm operations can reduce some of their environmental impacts by tailoring management strategies according to climatic forecasts.
Nitrogen Leaching and Seasonality
A case study: Model of a whole-dairy farm in north Central Florida
Winter season and the months of January and February are critical periods when the highest amounts of N leaching occur. Farmers and other stakeholders should pay attention to this period in order to protect the environment against N leaching. Several factors combine to increase leaching. Higher numbers of cows produce higher amounts of milk. Consequently higher amounts of manure N need to be disposed of. Finally, crops in the fields do not uptake N at full capacity because of lower temperatures and lower solar radiation. This problem is aggravated for El Niño years due to higher than normal rainfall events and higher than normal precipitation. General recommendations for this season are to decrease protein in diet as much as possible and to promote grazing of milking cows as much as possible./p> >
The N leaching concern is greatly reduced during summer time because crops in the fields are taking-up more nitrogen and the production of manure N from livestock is reduced because fewer cows are in lactation stage. This happens even though higher rainfall is registered in this period. Good management during this season is useful because it will have impacts over the following fall and winter seasons. It is important to maintain the crops in the fields well and promote their maximum uptake. Manure N should be applied in accordance with higher rainfall to avoid losses. Neutral years have higher rainfall amounts and consequently a slightly higher risk of N leaching than the other ENSO phases.
In fall the amount of N leaching increases somewhat because the amounts of manure N produced on-farm starts to increase at the same time that less plant uptake is noticed. There are relatively small differences regarding N leaching and ENSO phases. Although El Niño presents higher risks than the others in this season, neutral years can also be riskier in middle fall season.
Nitrogen Leaching and Crops
Perennial pastures such as bermudagrass and bahiagrass are in general good options to protect N from leaching to groundwater because of the dense root system they form, the stability they confer to the soil, and their high capacity of N uptake. Bermudagrass was a better N up-taker and higher biomass accumulator than bahiagrass. However, these two crops have a dormant period (winter) and are not considered as good as some other crops for feeding dairy cows. When present these grasses must be inter-cropped or sod-cropped with at least some winter forage. Bermudagrass and bahiagrass could also be over-planted during summer season with corn or sorghum for a more intense production system that will uptake more N. This could be a good strategy for neutral summers. When including a summer crop in the pasture, it is important not to destroy the pasture with the field preparations for the other crops.
Corn, sorghum, and millet are good N up-takers, good biomass accumulators, with medium N leaching. They can be planted in summer and/or fall during any of the ENSO phases.
Winter forages including oats, wheat, rye, ryegrass, and others, are in general low biomass accumulators and present a medium to high N leaching risk. In critical years such as El Niño years, inter-planting some or all of these crops (not uncommon) is recommended. These winter annuals will provide maximum N uptake per unit of area decreasing the N leaching risk.
Additional Resources
For more information about this study, please refer to the following files (better if you download the files to your local machine):
Dynamic North Florida Dairy Model (.xls 3.7 MB)
http://edis.ifas.ufl.edu/DS067