Unique process ‘cleans’ crop water runoff when using dairy manure as fertilizer

Dairy manure is a natural crop fertilizer, and Texas A&M AgriLife scientists believe they have discovered a way to make sure that the valuable resource stays on crops where it is applied as a fertilizer, and out of waterways, where it is a potential pollutant.
calendar icon 25 December 2020
clock icon 7 minute read

Texas A&M AgriLife Research and Tarleton State University scientists are joining forces to develop and demonstrate a biochar-assisted phytoremediation system for enhancing water quality during dairy manure application in the Stephenville and Vernon crop production areas. Biochar is a charcoal-like compound made through gasification from waste, including manure.

This “Biocarbon-enhanced dairy manure management demonstration for enhanced water quality” project is funded by the U.S. Department of Agriculture’s Natural Resources Conservation Service through the Conservation Innovation Grants, CIG, program.

The premise of the research is the specially designed biochar, created by using heat, pressure and other adjuvants, produces unique carbon structures tailored for dairy and other waste material. This unique biochar, when used in conjunction with growing plants, can help enhance the water quality of any potential runoff.

“The nexus between agriculture and water quality is incredibly important research, particularly in Texas,” said Patrick Stover, Ph.D., vice chancellor for Texas A&M AgriLife, dean of the Texas A&M College of Agriculture and Life Sciences and director of Texas A&M AgriLife Research. “These findings will further improve how we marry agriculture and health, and are a positive step forward toward understanding how we can make dairy manure a beneficial adjuvant to the ecosystem.”

Research partnership addresses regional issue

The project’s lead scientist is Eun Sung Kan, Ph.D., an AgriLife Research biological engineer at the AgriLife Research center at Stephenville with joint appointments in Texas A&M’s Department of Biological and Agricultural Engineering and at Tarleton State University. Kan concentrates his research on using a unique biochar he has developed to transform wastewater into water for agricultural needs.

“Not all biochar is created equal,” said Bill McCutchen, Ph.D., Texas A&M AgriLife Research and Extension Center director at Stephenville. “Some will bind phosphorus and ammonia better and also amend soil, so we not only help agricultural areas, but also prevent runoff of phosphorus and other contaminants into streams and reservoirs, which is the lifeblood between the rural-urban nexus.”

Joining Kan on the project are Jim Muir, Ph.D., grassland ecologist, and Barb Jones, Ph.D., dairy professor, both of whom also have joint positions with AgriLife Research and Tarleton State. Paul DeLaune, Ph.D., AgriLife Research soil scientist, Vernon, and Jeff Brady, Ph.D., genetics specialist, Stephenville, will also participate.

The Tarleton State University College of Agricultural and Environmental Sciences is particularly pleased about this grant, said W. Stephen Damron, Ph.D., dean of Tarleton’s College of Agricultural and Environmental Sciences.

“Not only is the work much needed, but the grant emphasizes the value of the AgriLife/Tarleton partnership,” Damron said. “Drs. Kan, Jones and Muir have joint appointments with AgriLife and Tarleton State University. By joining forces, we bring more person power and resources to the project to help ensure its success.”

Damron said Tarleton students also benefit, as several graduate and undergraduate students will work on the project gaining much-needed research experience and technical and analytical skills.

When too much of a good thing is a bad thing

Jones said on average, a dairy cow will secrete over 100 pounds of manure daily. So, the manure needs to be properly handled through nutrient management plans, which all dairies have on their farms.

Some farms vacuum the manure slurry from the barn and apply it directly to the land, weather and permits allowing. Other farms, including the Southwest Regional Dairy Center, use recycled effluent to wash the manure slurry from the barns. The flushed effluent travels through various stages to separate out bedding and manure solids before landing in the lagoon. Still other farms may scrape out manure slurry into manure pits.

“Manure is a valuable resource to the farm as it is rich in nutrients such as nitrogen and phosphorus,” Jones said. “Farms will use manure as a natural fertilizer to enhance plant growth.”

At issue is the manure’s nutrient content, especially its high levels of nitrogen and phosphorus. When manure is applied to fields, nutrients can potentially leach to groundwater or run off and accumulate in surface water bodies, resulting in algal blooms.

Kan said not only does the specifically designed biochar remove phosphorus and ammonia, but also provides agronomic benefits to the soil and plants by slowly releasing these nutrients as plants need them.

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

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

Field testing in regenerative agricultural cropping systems

Over the past few years, Kan has been perfecting this new biochar process. He has proven the concept in the greenhouse but not in the field, he said.

“These CIG grants are directed at applying technology that is already created and tested,” Muir said. “CIG provides the funding to take it from the research level to application in the field. This is an application project.”

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

The research will redistribute dairy nutrients on perennial forage-based systems on AgriLife Research property near Stephenville. In addition, some of the biochar will be transported to the Vernon area where DeLaune will look at its use in regenerative agriculture cropping systems.

“This project will allow us to evaluate the impact of this novel practice in perennial systems that have a long-history of dairy manure applications and typically sufficient soil phosphorus levels compared to cropping systems with deficient soil phosphorus levels,” DeLaune said.

Regenerative agriculture promotes reduced tillage and the use of organic nutrient sources, he said. This project will demonstrate a novel technology, and if utilized by both established and new adopters, it can improve sustainability.

“This project will allow for the evaluation of synergies among tillage systems, addition of cover/forage crops, and amended dairy manure on nutrient cycling and subsequent fate of nutrients in the soil profile and surface runoff,” DeLaune said.

Kan said field tests of biochar are ready to be conducted and they will begin with a culturally acceptable rate per acre. In addition, they will compare commercial biochar with the novel dairy manure kind at different rates.

What does biochar do in the field

Brady will study the microbial profile of the soil after applying the biochar, particularly looking at how bacterial communities in the soil fare under green manure versus biochar.

“If you add green manure or biochar to the soil, you change the microbial activity,” 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. Dr. Kan’s system ties up those nutrients to keep them from washing off and becoming a pollutant. We will be monitoring the soil for positive changes on the microbial community.”

Muir explained that some north Central Texas soils are very poor in nitrogen and phosphorus, and the surrounding dairies could provide copious amounts of those nutrients to an expanded land area through regenerative ag use of its manure. Typically, biochar must be incorporated into the soil to bind those nutrients. Answering how long that binding lasts and how gradually the nutrients are released for plant uptake are the applied aspects of this project.

As a forage agronomist and agroecologist, Muir said his focus will be on the integration of the biochar into forage production systems. Because the region’s climate and rainfall limit row crop production, the main focus is on livestock.

“A large percentage of our pastures are perennial Bermuda grass pastures, and you can’t take this biochar and apply it without tillage in those systems,” he said. “Most Bermuda grass pastures are already functioning, so that will be one of the challenges we will face: how to incorporate this into soils of perennial systems that are not tillable. We will also be looking at cost effectiveness.”

Following the research

The researchers maintain that the knowledge gained through this research project will provide solutions to improve the sustainability of animal-based agricultural systems and food security while enhancing environmental quality for future generations.

If successfully implemented, Kan said he expects that his unique biochar will be applied with other livestock manures.

“We are going to try to find equilibrium between the technology and costs,” McCutchen said. “Then we expect this will lead to larger-scale studies in other regions and with other confined animal manures.”

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