Study: Wood Chips Can Improve Paddock Soil Quality

Study: Wood Chips Can Improve Paddock Soil Quality

Using absorbent, biodegradable bedding materials in paddocks can keep nearby water sources cleaner while favoring healthy grass production.

Photo: Anne M. Eberhardt/The Horse

Wood shavings can make a stall cheerfully clean and fresh-smelling. But have you ever thought of putting wood chips in your paddock? The point might not be cheerfulness or good odors, but the practice certainly has benefits. Swedish researchers say adding wood chips to certain paddock areas can improve the paddock—and the environment.

Using absorbent, biodegradable bedding materials in paddocks can keep nearby water sources cleaner while favoring healthy grass production, said Masud Parvage, PhD, of the Swedish University of Agricultural Sciences’ Department of Soil and Environment, in Uppsala.

“The idea is to trap the nutrients within the bedding materials so that they do not leach out to the nearby streams and/or lakes,” Parvage said. As he noted in a previous study, high concentrations of feed and horse manure—in paddocks, for example—can degrade local water quality and upset the water’s natural balances.

But holding nutrients like carbon, phosphorus, and nitrogen in the paddock soil could keep the ground rich enough to produce grasses and other vegetation—even in moderate traffic areas.

“Though the horses walk all the time in the paddock, we observed a massive growth of grasses in the paddocks during the summer in Swedish paddocks (other than feeding areas),” Parvage said. “So keeping the nutrients in the soil might be good for grass growth.”

Nutrient-rich paddock soil can also be a great investment for the future if owners decide to turn or rotate that paddock for other purposes, he added. “Some farms shift their paddock to crop land after 10 to 20 years. So, in the long run, keeping the nutrients in the paddock soil will be beneficial for the crops, as well.”

But how do you keep those nutrients in land that’s constantly being trampled, rolled on, eaten on, and inundated with urine and feces? That’s what Parvage and his colleagues sought to find out when they tested three bedding materials’ ability to retain major nutrients. In an experimental setting inside a lysimeter station (a device for measuring water percolation through soil) equipped with artificial rainfall, they evaluated peat, wheat straw, and wood chips to see how well they held carbon, phosphorus, and nitrogen.

None of the three bedding types prevented the loss of all three nutrients, Parvage said. However, wood chips were most effective. They reduced phosphorus and carbon leaching by 70% and 40%, respectively (compared to no added bedding). Unfortunately, he noted, they didn’t hinder the leaching of nitrogen.

Meanwhile, wheat straw was completely ineffective for nutrient retention. In fact, Parvage said, in some cases, the straw caused an increase in leaching.

Peat held nitrogen in fairly well, reducing leaching by 40%, he said. However, those benefits were counterbalanced by the fact that peat caused multiple-fold increases in leaching of the other two nutrients.

“Wood chips can help maintain soil integrity in the paddocks and would be especially useful in the feeding and excretion areas,” Parvage said.

In their study the researchers applied wood shavings about 5 centimeters (2 inches) deep, which would be able to absorb about 20 millimters (3/4 of an inch) of rain. The shavings should ideally be changed about every three to four months, Parvage said. Discarded shavings can be added to regular manure piles and used for composting.

In geographic regions with high rainfall and poor evaporation (due to soil type and/or the season), owners might need to adjust shavings quantities through trial and error. “At the very least, in summer when rainfall is low and evaporation is high, the wood shavings should work well in the paddock for most types of soil.”

The study, “Can Organic Materials Reduce Excess Nutrient Leaching from Manure-Rich Paddock Soils?” was published in the Journal of Environmental Quality

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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