Truck and manure applicator

Editor’s note: The following was written by Rick Koelsch, University of Nebraska livestock environmental engineer, for the university’s Crop Watch website.

Roughly half of all neighbor complaints of livestock odors originate from land application of manure. A weather forecast and a little knowledge of odor dilution can be a powerful tool for keeping your neighbors happy, or at least avoiding those irate phone calls.

This article summarizes those weather conditions that should be considered when planning manure application.

Incorporation of manure into the soil is always the “best” practice for controlling odor. Soil is an excellent filter for removing odors released by manure. However, maintaining residue cover to protect soil quality, reduce erosion and conserve water does not always allow for manure to be incorporated.

When manure cannot be incorporated, the next 36-hour period after land-applying manure is the most critical. Why? Good drying conditions over the next two days can significantly reduce the release of odors.

Manure TOD chart

In addition, the next two evenings are the most likely time when neighbors will experience odors. Especially when applying manure without incorporating it, pay close attention to the forecast for the 36 hours after application.

Predicted wind direction

Wind direction is the single most critical information for selecting fields for land application of manure. Odor plumes travel in the same direction as wind and spread out laterally very little. By identifying the edges of the field perpendicular to the wind and the wind’s direction, one can quickly identify the neighbors at greatest risk and those unlikely to be impacted.

For example, choosing a land application site half a mile to the north for a southwest wind, risk can be dramatically reduced.

By paying attention to the wind directional forecast for a 36-hour period after applying manure, applicators can gauge the risk of odor affecting neighbors.

Evening hours

Can you recall a time when you observed a smoke cloud hanging near the ground? Often this is observed when air temperatures are cooling and winds are light, most commonly during evening and nighttime hours. Under these conditions the smoke is not being diluted and is being held near the ground.

Although we cannot see odors, the same atmospheric conditions create the greatest risk for neighbors experiencing odors.

Under daytime conditions, odor plumes are generally rising and diluted with fresh air to the point they are unlikely to be noticed by your neighbors. Bright sunshine and warming air are best for dispersing odors.

Higher wind speeds (especially at night) also encourage greater mixing of fresh and odorous air and reduce odor risk. Note that nighttime hours with low wind speeds are the conditions most likely to expose neighbors to odors from land application.