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Biochar studied for improving runoff-water quality

Biochar studied for improving runoff-water quality

A biochar system for enhancing water quality during dairy-manure application is being tested by scientists at Texas A&M AgriLife Research and Tarleton State University. A specially designed biochar produces carbon structures suited for manure and other wastes. When used with growing plants it can help enhance water quality of potential runoff. The biochar is created by using heat, pressure and adjuvants.

“Not all biochar is created equal,” said Bill McCutchen, director of the Texas A&M-AgriLife Research and Extension Center in Stephenville, Texas. “Some will bind phosphorus and ammonia better so we can prevent runoff of phosphorus and other contaminants.”

Some farms vacuum manure slurry and apply it directly to land – weather and permits allowing. Other farms such as the Tarleton State University-Southwest Regional Dairy Center use recycled effluent to wash manure slurry from barns. The effluent travels through various stages to separate bedding and manure solids before entering a lagoon. Still other farms may scrape manure slurry into manure pits.

Rich in nitrogen and phosphorus farms use manure as a natural fertilizer to enhance plant growth. But the nutrients can potentially leach to groundwater or run off fields and accumulate in water bodies.

The specially designed biochar removes phosphorus and ammonia. It also provides benefits to soil and plants by slowly releasing the nutrients as plants need them, said Eun Sung Kan, the project lead and a biological engineer at the Stephenville center.

“Several previous projects applied biochar to make plants grow and to fertilize soil,” he said. “But no one has demonstrated how it enhances water by removing pollutants from runoff. The biochar process eliminates contaminants and pathogens. In this project we have a special biochar we crush into a powder and spray on a crop. It mixes with the soil to remove phosphorus, ammonia and active bacteria that pollute waterways as runoff.”

The biochar should enhance plants’ ability to recycle nutrients from the soil, a process called phytoremediation, said Jim Muir, a professor of grassland ecology at Tarleton State University.

“Our proposal uses biochar to stabilize the nutrients until pasture plants have time to absorb and use them,” he said. “Then dairies can feed the plants to cows, completing the cycle.”

The project will determine the efficiency and economics of phytoremediation on reactive nitrogen and phosphorus from dairy manure in water and soil. The team will integrate field-scale research, laboratory analyses and systematic evaluation.

Manure will be applied on perennial forage-based systems near the center. Some of the biochar also will be transported to an area where it will be studied for use in regenerative-agriculture cropping systems.

“The project will allow us to evaluate the impact in perennial systems that have a long history of dairy-manure applications and typically sufficient soil phosphorus levels compared to cropping systems with deficient phosphorus levels,” said Paul DeLaune, a soil scientist with Texas A&M AgriLife Research.

Regenerative agriculture promotes reduced tillage and the use of organic-nutrient sources. The project will allow for the evaluation of synergies among tillage systems, addition of cover crops or forage crops, and amended dairy manure on nutrient cycling, DeLaune said. It also will enable researchers to study the fate of nutrients in the soil profile as well as surface runoff.

The soil’s microbial profile after biochar application will be studied. Jeff Brady, a genetics specialist for Texas A&M AgriLife Research, will study how bacterial communities in the soil fare with green manure versus biochar. Microbial activity changes when green manure or biochar are added to the soil, he said.

“Nitrogen and phosphorus are good for plants, but there’s too much of a good thing when you apply green manure to the soil,” he said. “Dr. Kan’s system ties up those nutrients to keep them from washing off and becoming a pollutant. We will be monitoring soil for positive changes on the microbial community.”

Some soils are very poor in nitrogen and phosphorus. Dairies could provide copious amounts of those nutrients to an expanded land area. Biochar typically must be incorporated into soil to bind the nutrients. How long the binding lasts and how gradually nutrients are released for plant uptake are applied aspects of the research project. Visit agrilifeextension.tamu.edu for more information.

Kay Ledbetter is a communications specialist for the Texas A&M AgriLife Research and Extension Center in Amarillo, Texas.

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