Manure nutrient application takes good management

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Writing this article has been on my schedule since March 2014. At that time a reminder on this topic would have been reactive, not proactive. This year we all can be proactive.

The late winter and early spring last year was a time when a large number of manure releases occurred. During a two-week period in March, over 20 releases were reported in the southcentral region of Pennsylvania. Some of these were manure storages that overtopped and some were results of manure application during high-risk periods.

Winter weather repeat?

If you can remember the weather from last year, then this year may seem like a repeat in your mind. Certainly one of the largest risk factors associated with manure storages at this time of year stems from holding capacity.

Most producers do a fine job of drawing storage levels down in the fall to assure space for manure accumulation over winter months. The same management integrity and desire not to pollute can lead to manure application to lands that are not in ideal condition to accept manure. This is completely understandable. Why allow overtopping to act as a point source manure release when land application may prevent the release?

Curb runoff

This brings us to the other avenue of manure loss that should concern every producer: the loss of land-applied manure. Remember that your manure nutrients have great value. Change your thought process — and perhaps your everyday terminology — from manure application to nutrient placement.

Apply manure nutrients where you want them and in a manner that assure they stay where you place them. Manure nutrients that move past the field edge do no good for crop production and are pollutants. Frozen soil and snow cover increase risk of nutrient loss. Melting snow and precipitation are less likely to infiltrate frozen soil, increasing runoff.

Once thawed, spring soils are slow to dry due to low temperatures and lack of plant evapotranspiration. Saturated soils do not have pore space for water to infiltrate. Both nitrogen and phosphorus in manure come in soluble forms. When water leaves a manured field, these nutrients can travel with the water, even if the water appears clear. If runoff appears cloudy or brown, you can be sure that your nutrients are leaving the place where you placed them.

All about the timing

So what are some recommendations for keeping manure nutrients in a place where they are available to the coming crop? I will answer this question in general terms, without state-specific regulatory guidance. The caveat is that you should know the regulations for where you are working.

The best strategy is timing of the nutrient placement. If you can hold on to the manure until a time close to crop nutrient demand, you increase nutrient use efficiency, while minimizing risk of loss.

Winter applications

Of course, the real driver of this article centers on good practices for situations where manure application must occur before this ideal time. If you must apply manure during the late winter or early spring, then be aware of your state’s definition of winter.

Winter application regulations, understandably, come with restrictions. Application must occur within the guidance of the appropriate manure or nutrient management plan. Application outside of this guidance could lead to enforcement actions, especially if a manure loss occurs. For winter application, the placement of nutrients should occur in a field designated for winter application in the plan.

Cover slows movement

Items that help to hold nutrients in place include application to shallow slopes and lands with lots of ground cover. More ground cover will help to hold manure particles and nutrients in place. Slowing movement of water across the land allows for greater infiltration of soluble nutrient fractions. Cover can include established perennial crops like hay, established cover crops or heavy crop residue.

Setbacks

Distance is another tool to minimize loss from a field. Application setbacks should be followed. Exceeding setbacks at this time of year can be warranted.

Pay attention to weather forecasts. Predicted precipitation can have obvious impacts on manure movement, especially on already frozen or saturated soils. Warming trends can also bring risk, especially if combined with precipitation. Rising temperatures, coupled with rain, are exceptionally dangerous.

Skip swales

To this end, the applicator is wise to skip even subtle swales in otherwise safer or approved winter application lands. These shallow swales can act as water channels during these extreme runoff events and nutrients placed there are sure to leave.

Keep learning

Technology and techniques in the manure handling and application industry continues to advance. Learn more about these advancements at the 2015 North American Manure Expo in Chambersburg, Pennsylvania, on July 14 and 15. Commercial vendors, who bring their newest equipment for trade show display and demonstration, support the event. The Manure Expo will include a tour day of area farms that implement strategic manure planning or treatment systems. There will also be a manure agitation and dragline demonstration.

Visit manureexpo.org in the coming months to select which of the overlapping agenda items you want to attend. Choose carefully, because the theme of this event is 2015 Manure Expo: Manure than you can Handle.

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Robb Meinen is a senior Extension associate in the Department of Animal Science at Penn State University. He coordinates education for the Pa. Commercial Manure Hauler and Broker Certification Program.

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