Low disturbance application has benefits

We can incorporate manure to capture nutrients without raising the risk of erosion.

by Eric Young

Tillage and manure application are critical nutrient management aspects affecting crop yield potential, soil erosion, and nutrient loss risk. Besides raising erosion potential, tillage over time also influences soil organic carbon accumulation or loss, soil structure, compaction potential, and overall soil quality.

Mitigating soil erosion makes economic and environmental sense because long-term erosion reduces crop yield potential and can contribute to impaired water quality when sediment and nutrients in runoff are transported to surface water. It is well established that reducing tillage decreases erosion, particularly on moderate to steeply sloping fields with high erodibility.

In corn silage systems, tillage practices depend on climate, soil characteristics (texture, drainage, and slope), and other farm-specific factors. Individual farm tillage practices may also vary by specific fields/soil types, and over time depending on weather, crop rotations, and compaction.

In cold climates with poorly drained soils, tillage helps dry surface soils, break up clods, relieve surface compaction, and prepare a consistent seed bed. While reduced tillage is possible on imperfectly drained soils, strict no-tillage is more common on welldrained soils where aeration is not typically limiting.

Preparing for application

Tillage sets the stage for manure management. In conventional systems, manure is typically broadcast on the surface and incorporated via a primary tillage tool, such as a chisel plow, or secondary tillage tool, like a disk, harrow, or field cultivator.

While effective at reducing ammonia volatilization and surface runoff nutrient loss, tillage incorporation has higher erosion potential compared to lower disturbance application methods. In addition, some studies suggest that long-term reduced tillage should further cut back erosion/surface runoff due to greater water infiltration rates from repeated lack of tillage.

Low disturbance manure application (LDMA) attempts to achieve the conservation and soil quality benefits of reduced tillage (lower erosion and soil disturbance) while conserving ammonia nitrogen and mitigating runoff nutrient loss potential in the way conventional tillage does. LDMA equipment is engineered to minimize horizontal soil shearing and disturbance, leave more crop residue on the surface, and place manure beneath the soil surface or encourage infiltration to enhance manure-soil interaction.

LDMA has focused mainly on applying liquid manures. Commonly used LDMA implements include applying manure in bands (banding) with or without aeration (banding/aeration), sweep injection, shallow disk injection, and various drag hose systems.

By definition, broadcast-surface application is low disturbance as it causes minimal disturbance during application; however, ammonia-nitrogen is rapidly lost without incorporation, and nitrogen (N), phosphorus (P), and other nutrients remain shallow and vulnerable to transport in surface water runoff.

For corn or hayfields

LDMA can work in both corn and hay crop rotation phases. Previous research led by the USDA Agricultural Research Service (ARS) compared surface runoff water quality from corn-winter rye plots under the following treatments:

1. No manure (control)

2. Broadcast-surface application

3. Broadcast-disk incorporation

4. Banding/aeration

5. Sweep injection with strip till Results showed that strip till injection had 84% to 99% lower P losses compared to broadcast soon after fall manure application. Aeration/banding also reduced ammonium and dissolved P, but it was not as effective as strip till injection for total P and N, similar to the broadcast-disk treatment. Average runoff total P, dissolved reactive P, and ammonium-N concentrations did not differ statistically between strip till injection and the no-manure control, suggesting injection mitigated surface water quality risk more than the other methods for runoff events soon after manure application.

Another important aspect highlighted by this study was runoff timing relative to manure application. In the two spring runoff events, total N and P concentrations dropped substantially compared to fall, with few significant differences between methods. Timing and method also affect the amount and distribution of soil nutrients and crop yield potential. While yield was not part of this study, a separate four-year ARS trial showed that fall-applied manure via strip till injection produced similar corn silage yields to spring-applied fertilizer N, indicating injection conserved more N compared to other application methods.

A main concern with LDMA in hay crops is plant damage and yield loss. Encouragingly, studies in the U.S. and other countries report relatively low risk of stand injury under low application rates and done under proper conditions. In mixed alfalfa-grass plots in central Wisconsin, recent work led by ARS indicated that runoff total N and P for shallow disk injection was significantly lower than the aerator/ band treatment and similar to the no-manure treatment.

Like broadcasting manure, LDMA after hay harvest is ideal before any regrowth occurs. Soil moisture status is an important factor to consider anytime manure is applied, and especially for LDMA. Studies indicate that banding/aeration on wet soils is ineffective and could even exacerbate runoff potential by causing compaction and reducing infiltration.

Applying liquid dairy manure after hay cuttings is a common practice and provides an important source of N, P, sulfur, potassium, and other nutrients. However, without immediate injection or incorporation, greater than 80% of manure ammonia-N can be lost within 24 hours of application, reducing the agronomic value. While N loss from lack of incorporation may not be as much of a concern for more leguminous stands, nutrient loss risk is still worrisome since broadcast manure (liquid or semi-solid) is more vulnerable to runoff. Another consideration is P accumulation from repeated manure applications and lack of tillage to redistribute P. Depending on soil test P levels and runoff risk, P accumulation from LDMA may or may not be an issue.

Keep nutrients in place

The bottom line is that LDMA offers several agri-environmental advantages over broadcasting and/or broadcast-till.

Broadcasting without incorporation may seem faster and cheaper, but it may not be more cost effective when factoring in lost N. It is also a high water quality risk compared to incorporation. LDMA mitigates tillage-related erosion and leaves more residue compared to conventional tillage.

Evaluating the suitability of LDMA must consider N savings and the lower environmental risk in addition to greater time, labor, and equipment needs. Future work should consider both economic and environmental aspects of LDMA to help farms determine their most efficient manure management strategies. ■ estled in the foothills of central Georgia, the Cooley family raises chickens and crops on their farm near Roberta. While biosecurity concerns limit the opportunity for visitors on many poultry operations, the Cooleys have always valued consumer education. From their animal care to litter management, transparency and sustainability are permanent parts of their agriculture story.

The author is a research soil scientist for the Institute for Environmentally Integrated Dairy Management, USDA-Agriculture Research Service.

The Cooleys’ efforts were recognized nationally, as they were named USPOULTRY’s Family Farm Environmental Excellence Award winner in 2011. The award recognizes farms in poultry and egg production for exemplary environmental stewardship.

Terri and Larry Cooley purchased the farm in 1985. A year later, they put up two chicken houses and then two more a few years later. They doubled in size to eight houses in 1995.

After their son, Leighton, returned home from college in 2005, they built four more houses. Today, there are 16 broiler houses spread between three sites. Leighton is the second generation to own and operate Cooley Farms, but he is actually a fourth-generation poultry producer, as Terri’s grandfather and father were farmers, too.

The Cooleys raise chickens for Perdue Farms. Their operation has capacity for 500,000 birds at one time. They raise six flocks per year, finishing about 3 million birds annually.

In their relationship with Perdue, they receive chicks at one day of age. The Cooleys raise the birds for 42 days before they are shipped to Perdue’s facilities to be processed. Pay is determined based on an average price per pound of live weight, ranked against the weight and feed conversion rate of other farms selling birds that week.

The Cooleys explained that there are three main components of a chicken house: temperature, water, and air. While those basics are still at the core, building design has advanced over the years. The Cooleys have made investments over time to improve their chicken houses, which are 45 feet wide by 600 feet long.

“Technology in the poultry industry has made leaps and bounds,” Leighton said. For example, their tunnel-ventilated barns now pull air through cooling cells to help moderate the temperature in the barn during the long, hot Georgia summers. “In the summer, we used to see increased mortality (due to the heat), but now we see just a slight dip in performance,” Leighton said. “A comfortable chicken is going to be a better growing chicken.”

There are central controls for each house, and this information can be accessed on a computer, smartphone, or tablet. The Cooleys can get a live snapshot of what is going on in each barn at any moment. “We used to say we grew chickens by the day, but now we grow them by the minute,” Leighton said.

Continuous access to feed, water, and fresh air is a necessity in a poultry barn, so every barn has a backup generator that takes over in a few sec- onds if the power goes out. They also do a lot of preventative maintenance to keep everything up and running.

Even with all the technology advancements, the Cooleys emphasized the important human element in raising chickens.

“Technology doesn’t replace human interactions, it just enhances it,” Leighton said. Along with his parents,

Leighton works daily with their crew of three full-time employees to care for their flock. They also raise 165 Angus beef cows and run 1,000 acres of hay land, pasture, and timber. Leighton’s wife, Brenda, and older sister, Amanda, work in education but return to the farm to help when needed, especially during the summer months. His younger sister, Courtney, and her husband, Jones, operate their own poultry, beef, and small grains farm.

The benefits of litter

Much of the manure produced by their broilers is recycled and utilized as bedding, commonly known as litter. In fact, the Cooleys estimate that some of the composted litter in their barns is four years old.

In between flocks of birds, each barn stands empty for two to three weeks. During that time, the floor is prepared for the next group of broilers.

First, they use a decaker to sort out the wet litter or cake. The machine sifts and shakes the litter as it moves through the barn. The material that remains is placed into two three-foot tall windrows. After three days and two turns, those windrows reach a temperature of 130°F, which composts the litter. Then the litter is leveled throughout the barn. Additional shavings are added if needed, but Leighton noted the benefits of the litter buildup.

“It makes a better base, and it provides natural immunity for young birds,” Leighton said. He also shared that the 5 inches of litter they provide as a base is better for the broilers’ feet and legs, which is very important when it comes to raising birds.

A dry floor is key, as wet litter creates moisture and ammonia in the air. Their ventilation system can exhaust this out, and a poultry litter treatment to neutralize ammonia can be used if needed.

Litter that leaves the barns is put under one of three stack barns. These are open-ended barns with concrete floors where manure is stacked and used or sold. Some of the manure is spread on their pastures and hayfields; the rest is sold by the ton and custom applied.

Their pastures receive litter exclusively, but forage fields will be supplemented with some commercial fertilizer as needed. The Cooleys test their litter annually, and they said the nutrient content stays pretty consistent.

Better than ever

Poultry manure is high in nitrogen and phosphorus, so it is a useful fertilizer, when applied appropriately. Since 2011, the Cooleys have used GPS to apply litter to their land.

“There are a lot of variables in manure spreading,” Leighton said. “We wanted to add consistency to something that can sometimes be inconsistent, and using GPS was something we could control.”

The Cooleys have a nutrient management plan for each of their farms, and they have improved their record keeping over time, documenting how much they were applying, where, and when.

They also look for opportunities to do better. “We try to stay educated on practices we should or should not do,” Leighton said.

The Cooleys’ stewardship goals are very personal, as they want to see their land flourish in the future for Larry and Terri’s nine grandchildren, who love being on the farm.

“The farm is in better shape, by leaps and bounds, than when Mom and Dad moved here in 1985,” Leighton said. “That’s our vision of sustainability; not only leaving everything better than when we found it, but offering an opportunity for the future.”

From the inside out

The Cooley family has offered tours of their farm for the past three decades, but after visiting Hayden Farms, an operation in Kentucky that had a viewing area in one of their broiler houses, Terri wanted to do more to enhance the educational experience on their farm. She started doing research and presented the idea of incorporating an educational center on the farm to Larry and Leighton.

“We all understand the importance of educating and advocating about agriculture,” she explained. “Poultry farms are hard to see for biosecurity reasons. It’s difficult to introduce consumers to chicken houses, and that leads to misconceptions.”

Once the family agreed to venture down this path, the Cooleys built a 20-by-30-foot room with floor-to-ceiling windows in one of their poultry houses. They made the educational center look like a real chicken house, with waterers, feed lines, and so forth.

The educational center officially opened in October 2019 with a grand opening celebration, and since then they’ve hosted school field trips, legislators, bloggers, and others for tours.

“Transparency is really important to us,” Terri said. “We think there is a need to let people see what we do.”

Another unique opportunity to teach about agriculture presented itself to Leighton a few years ago. Their stewardship practices caught the attention of producers working on a documentary called “Farmland.” They were looking for six young farmers and ranchers around the country to share their experiences and talk about modern agriculture.

Leighton talked to his family first and then eagerly accepted the opportunity. “We are always willing to open our doors to share our story and the pride we take in producing food.”

He was very pleased how the film turned out and for the chance to promote agriculture on a national stage.

“It was a really cool experience,” he said. “It was an opportunity we never saw coming to share our story.”

Beyond education, being a good neighbor is also very important to the Cooley family.

“We try to be careful and be the best neighbors we can be,” Leighton said.

Terri added, “We have been part of this community for 40 years. We take what our neighbors think of us seriously, because we live here, too. We are very fortunate to live in this community.”

Farming in the hot climate of Georgia just 70 miles from Atlanta brings its challenges, but the Cooleys are thankful to pursue their agricultural passions on the farm Larry and Terri started 35 years ago. While incorporating technology helps them better care for their animals and the land, it’s the human element in both raising broilers and communicating with the public that the Cooleys value most. ■