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Climate change impact: Manure management

Tamara Scully for Progressive Dairyman Published on 11 March 2016
Manure management

Farmers need to assume climate change will cause changes in weather patterns and that it will require them to make changes.

Efficient production is the key to lower agricultural greenhouse gas (GHG) emissions while producing food to feed a growing population, said Peter Wright, retired New York State conservation engineer, USDA-NRCS. Manure management will be a primary focus of climate change adaptation.

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“If we don’t have the science behind this, we’ll end up with policy that may or may not be a good fit for agriculture,” Wright emphasized. “We need technology before the policy,” and there is a need for new technology to address climate change concerns.

Seasonal handling

Climate models predict wetter winters, drier summers and an increase in storm frequency and intensity in the Northeast. Winter weather variability will cause runoff events as melts, which occur after the ground is frozen, become more common.

At the same time, increased environmental concerns about water quality and quantity, as well as a focus on the removal of organic wastes from landfills, will occur. Winter manure spreading restrictions will increase as water quality concerns become a primary focus, and windows of opportunity for manure handling will decrease.

Farmers absolutely will have to adapt their manure management practices.

Handling manure properly requires enough storage so the manure is applied under conditions that favor its incorporation into the soil. The reality is: Manure storage all too often gets filled and causes manure to be spread at “inopportune times,” causing runoff concerns. Increasingly wet springs caused by climate change will keep fields saturated and limit spreading opportunities.

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Wetter winters will only enhance this issue. Manure storage design will need to include additional storage for wetter weather and enhanced environmental regulations.

Frost injection of manure is one technique that currently works well in the winter, when conditions are right. Frozen ground allows application without compaction, and injecting the manure below the frost prevents runoff.

When the ground melts from the bottom up, as happens when there is some frost, then runoff is not an issue. Frost injection works because the soil a few inches below the surface is still dry and warm.

When the ground melts from the top down, however, runoff happens. Wetter winters and temperature variations may alter the freeze-thaw cycles. Changing weather patterns and extremes will make timing for frost injection difficult. Without options for winter application, manure storage will become even more important. Using technology to enhance storage abilities is a good approach to take, Wright said.

Manure storage covers provide the ability to capture rainwater and pump it off, keeping it out of the manure and reducing the need to haul and spread it. Covers can offset manure handling costs “because you’re not hauling all that liquid,” Wright said.

Covers also capture GHG emissions, which can be flared off. And if solids are separated out of the manure, they can be used in bedding or used on the farm – or sold – for compost.

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With proper storage volumes, manure can be spread in the summer, when grounds will be dry. This will lessen compaction and runoff concerns and supply nutrients closer to the time crops will actually utilize them.

But summer manure spreading brings complications, too.

Odor issues, as well as crop contamination issues, are concerns with summer manure application. Technology can help with these concerns. Adding an anaerobic digester increases manure storage capacity and reduces manure odor. It also generates renewable energy.

When manure is applied to growing crops, it is a fertilizer, Wright said. Double-cropping, which will be more practical as warming trends increase the growing season, will allow for more nutrient uptake so manure can be applied at different times during the growing season.

“Let’s figure out ways to incorporate manure in the summer,” Wright said.

Application technique

Techniques to apply manure below crop canopies can make growing season applications viable. Nutrient booms with draghoses can deliver manure to the soil surface while crops are growing. Spreading manure after hay cuttings can work. Injecting manure after cutting is another option.

Drier summers will require increased use of irrigation. The potential to adapt irrigation systems to handle manure exists. Reducing solids content to about 4 percent, to allow pumping, would be needed.

Problems arise when soils can’t take up the nutrients in the applied manure. Uniform application rates, as well as the infiltration rates, of the manure is an important factor, no matter which techniques are implemented.

Better controlling tile drainage by increasing tile drainage volumes during plant growth and blocking drainage after harvest will impact nitrous oxide and phosphorous release. Adding bacterial treatment systems to the end of the tiles will further alleviate nutrient runoff concerns.

Green energy

Wright predicts the demand for biofuel will offer farmers an opportunity to grow energy crops in a double-cropping system, bringing in added income. Anaerobic digesters can create renewable energy through captured biogas.

The energy and byproducts produced can potentially be utilized on- or off-farm, maximizing the value of manure. Anaerobic digesters reduce methane, too.

Farmers with anaerobic digesters may be able to accept organic waste, “mix it with manure and apply it to land. Soon organics will be restricted from landfills,” Wright said. This could provide other opportunities for farms to receive payment for processing organic wastes.

Climate change will cause farmers to adapt manure management practices. It will also present opportunities to improve farm GHG emissions, enhance on-farm conservation measures and possibly add income streams and profitability.

Soil health issues, water quality concerns and producing “higher yields on the crop acreage that we have” will require farmers to better manage manure. Changes in weather patterns will impact how manure can be managed without causing environmental concerns and will require adaptation in manure storage and handling.

Meeting the demands caused by climate change requires increased use of technology. The agricultural industry will need to be pro-active, implementing its own strategies and reducing the environmental impact of its practices.  PD

Peter Wright spoke at the Dairy Environmental Systems and Climate Adaptation Conference held at Cornell University in July 2015.

Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural and food system topics.

ILLUSTRATION: By Kristen Phillips.

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