Research project shows calibration is key to spreading manure for maximum effectiveness

Dr. Brent Auvermann, AgriLife Extension environmental systems specialist, said the main purpose of the project is to demonstrate how best management practices can be used to protect water quality.

The project is operating under the authority and funding of the Texas State Soil and Water Conservation Board through the U.S. Environmental Protection Agency’s 319 nonpoint source water quality program.

“This is about nonpoint source pollution, which is any pollution you cannot trace to the end of a discharge pipe of some kind,” Auvermann said. “Diffuse runoff from agricultural fields falls into that category. So we are trying to prevent or mitigate nonpoint source water pollution through the use of beneficial management practices for manure and compost application.”

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“Feeding cattle has been an integral part of the Texas High Plains economy for the past 40-plus years,” said Ben Weinheimer, Texas Cattle Feeders Association vice president. “Custom manure and compost haulers are important to the long-term success of cattle feeders.

A number of companies in the region provide manure/compost removal, hauling and spreading services, Weinheimer said. These independent contractors market manure and compost, primarily to farmers in the region. In recent years, feedyards have been able to sell manure due to its increased competitiveness with commercial fertilizer.

“TCFA’s interest in this project is to assist a key supporting industry by demonstrating field-proven techniques for proper application of manure and compost,” he said. “These include proper calibration of spreading equipment, best management practices for environmental protection and training resources for owners and employees of manure/compost companies.”

Auvermann said they are developing and refining management techniques of manure application, including developing a system by which manure haulers can easily calibrate their trucks and the applications they make if they don’t have electronic management capability.

The project has sites on watersheds in Wheeler, Donley and Deaf Smith counties along the Sweetwater Creek, Buck Creek and Palo Duro Creek, respectively.

“The No. 1 environmental challenge is making sure feedyards have enough land to put manure on,” Auvermann said. “One way to do that is off-site or third-party manure transfer. These transfers to third parties are really a critical component of a feedyard’s nutrient management planning exercise.

“In order to preserve that conduit for manure off the feedyard, we have to make sure that everyone involved in spreading manure knows how to spread manure uniformly, how to hit the target application rates and what areas of the field to avoid. That’s what this demonstration project is all about,” he said.

Dr. Paul DeLaune, AgriLife Research soil scientist in Vernon, said the project is looking at different rates of manure and compost applications, and documenting the effect of different rates of soil nitrogen and soil phosphorous and how it correlates to crop yields.

“And then also we want to monitor not only the soil nutrients, but how much nutrients we are losing in runoff water,” DeLaune said. “We have an automatic water sampler to collect water runoff samples during a storm event or even an irrigation event.”

He explained that if irrigation or storms produce runoff, the water runs through a flume on the backside of the sampler and they are able to calculate runoff volume based on that. In addition, they are able to take water quality samples.

“We have four rates: 20 tons raw manure per acre that is applied once every three years; five tons per acre of compost annually; commercial fertilizer applications annually, which is about 125 pounds of nitrogen; and then we have 10 tons per acre of raw manure application, which occurs annually,” DeLaune said.

The initial reports in year one with no storm-driven events, but with irrigation-driven events, indicate there is potential to move small amounts of nutrients off the plots even through irrigation, he said.

“We’ve seen as much as 11 pounds of nitrogen lost and about 7 pounds of phosphorous lost from a site – less than 2 percent of applied and soil nitrogen and phosphorus – just due to irrigation that is moving off site,” DeLaune said.

“The most important thing is to soil and manure sample,” he said. “Know how much nitrogen and phosphorous you have in your soil profile and how much is in the manure before you go and apply more.”

“Manure is a great source of macronutrients, micronutrients and organic matter,” Weinheimer said. “By providing these companies with the resources needed to be informed and making training resources readily available to them and their employees, we can ensure that manure is not at a competitive disadvantage to commercial fertilizer.

“Farmers should have the freedom to obtain crop nutrients from manure, compost or commercial fertilizer,” he said, adding they should also feel comfortable that the product has been applied in accordance with best management practices.

Provided by Texas A&M AgriLife