Manure Minute

MANURE VALUES CHANGE OVER TIME

Laboratory analysis is the best way to evaluate the nutrient content of manure on a specific farm. When sampling is not or cannot be done, farmers rely on “book values” to develop nutrient management plans, design manure storages, and create best management practices for land application. Book values show a range of nutrient values that can be expected from typical manure storages, but many of these averages are decades old and may not reflect current production practices. Factors such as animal diets, genetics, housing, and manure handling and storage all impact the nutrient content of the manure.

Researchers from the University of Minnesota set out to evaluate the change in manure from when the Midwest Plan Service last published its Manure Characteristics booklet in 2004. They partnered with three laboratories in the Midwest that shared data from the last 10 years. Nutrient averages for beef, dairy, poultry, and swine manure were evaluated.

For the liquid dairy samples, there was a decreasing trend over time for nitrogen and phosphorus and an increasing trend for ammoniumnitrogen. In liquid beef manure, there was a rising trend for more nitrogen, ammonium-nitrogen, and phosphorus. The liquid poultry manure had an increasing trend for ammoniumnitrogen and potassium with reducing levels of phosphorus. Without knowing more details about the liquid swine manure samples, including age of the animals and the type of manure storage system, the researchers were unable to determine nutrient changes.

For solid manure from swine, dairy, and beef operations, they found an upward trend for total nitrogen, phosphorous, and potassium. The solid poultry manure had a rising trend for total nitrogen and potassium.

The team recognized that knowing more details about the samples would be beneficial, since animal age, nutrition, housing, and manure storage can impact nutrient levels. The project’s next step is to formulate a manure nutrient database, called Manure DB, to help keep book values up to date. ■

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Manure irrigation deserves a retrial

Irrigation of liquid animal manure has a reputation for elevating ammonia loss, but research has proven otherwise.

by John P. Chastain

Large-bore traveling gun and center pivot irrigation systems have been used to apply treated lagoon water, liquid animal manure, and untreated slurry from swine and dairy farms in many parts of the United States. The primary advantages of using irrigation equipment to spread manure on cropland are the lower costs for energy and labor and the higher speed of application as compared to using a tractor-drawn spreader. The primary disadvantages are related to greater odor release and the possibility of spraying manure on roads or another person’s property.

The loss of nitrogen

The amount of nitrogen lost to the air as ammonia from application of manure is important for two reasons. From the farmer’s point of view, the loss of nitrogen as ammonia gas represents fertilizer that could have contributed to the production of a crop.

From an environmental point of view, ammonia lost from a field to the atmosphere is a source of air pollution that can combine with sulfates and nitrates to form extremely fine particulate matter that can have harmful effects on human health. This particulate matter can also contribute to water pollution when deposited into surface water by rainfall.

A previous study and several extension publications state that irrigation of animal manure raises ammonia-N loss by 10% to 25%. It was thought that using irrigation to apply liquid manure resulted in higher ammonia loss as compared to application to a field with a spreader. This additional ammonia loss was assumed to occur as the manure traveled through the air from the end of the irrigation nozzle and before it struck the ground.

Consequently, some government agencies have discouraged irrigation as a means to fertilize cropland with manure or have prohibited it completely due to concerns over an increase in ammonia emissions. Such regulations have a significant negative impact on dairy and swine producers who have invested in high levels of manure treatment that result in large volumes of dilute, liquid manure with low concentrations of nitrogen, phosphorous, solids, and minimal odor potential. Pumping diluted liquid manure through pipes to irrigation equipment is typically the most costeffective means to use the water and nutrients to grow crops.

For many years it has been assumed that more ammonia nitrogen was lost if irrigation was used to land apply liquid manure as compared to application with a spreader. Some governmental agencies have outlawed irrigation as an option even if manure treatment methods have been used to reduce the nitrogen content and odor.

A closer look

A meta-analysis of 55 data sets from three independent sources was performed to quantify the ammonia-N lost during the interval of time from when the liquid manure exited the irrigation equipment and when a sample was collected on the ground. The study included data for irrigation of untreated liquid and slurry manure, surface water from treatment lagoons, and very dilute effluent from an oxidation ditch that was used to provide advanced treatment for cattle manure. The data set also included three types of irrigation equipment: a traveling big gun, large-bore solid set sprinklers, and center-pivot irrigation.

The data included measurements of the total solids content (TS, %), the total nitrogen content (TKN), and the total ammoniacal nitrogen content (TAN). The total ammoniacal nitrogen is the sum of the ammonium nitrogen, which is a good source of fertilizer, and the ammonia nitrogen, which is the part that can be lost to the air as a gas. Fortunately, most liquid animal manure has a pH near 8, and only 8%

TOTAL AMMONIACAL NITROGEN IN IRRIGATED AND GROUND COLLECTED SAMPLES

John P. ChastainGround collected TAN (ppm)

1,300 1,200 1,100 1,00 900 800 700 600 500 400 300 200 100 0

TAN g

= 0.9999 TANI R2 = 0.9844 n = 55

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300

Irrigated TAN (ppm)

Figure 1. The concentration of the total ammoniacal nitrogen (TAN = ammonium-N + ammonia-N) was not changed as the manure traveled through the air. This was indicated by a regression line slope that was not significantly different from 1.0. The data included in the analysis was slurry manure, treatment lagoon water, and highly treated liquid manure. Manure that received the highest amount of treatment had the lowest concentrations of TAN.

to 10% of the TAN is ammonia nitrogen.

In each of the studies, samples were collected from the manure that was irrigated onto a field, and samples were collected in containers placed in the field to catch the manure on the ground. The differences in these concentrations were analyzed to determine if the TS, TKN, or TAN had changed significantly as the result of irrigation alone.

The first step was to determine if any water evaporated during irrigation by analysis of the TS data. Well-known data, used in irrigation design, indicates that evaporation loss during irrigation ranges from 1% to 3.5%. It was determined that evaporation losses for all 55 data sets was small and averaged 2.4%, which agreed with expectations for irrigation.

Consider the impacts

The same type of analysis was done for the total nitrogen data. Total nitrogen includes the organic nitrogen and TAN. The results indicated that irrigation did not significantly alter the concentration of TKN. On the average, the TKN content of the ground-collected samples was slightly higher than the irrigated samples, which was obviously impossible.

The plot of the TAN concentrations collected on the ground and the TAN contained in the irrigated water is shown in Figure 1. The results showed that irrigation of manure did not result in a change in the concentration of TAN. On the average, the TAN concentrations in the irrigated and ground-collected manure differed by only 0.01%. Therefore, no ammonia nitrogen was lost from the manure during irrigation.

The results of this study do not imply that ammonia volatilization after manure strikes the ground is to be ignored. The suitability of irrigation as a liquid manure application method should be evaluated based on the level of treatment and the potential impact of odors on neighbors. Also, the irrigation system should be designed and operated so as to prevent overspray onto roads, property owned by neighbors, and any type of surface water. In addition, irrigation of liquid manure must be delayed if runoff begins.

Application methods that reduce ammonia loss and odor, such as band application, direct injection, or similar nitrogen conserving methods, are recommended if untreated slurry manure or lagoon sludge is to be used as a natural fertilizer substitute. 

Reference: Chastain, J.P. 2019. Ammonia Volatilization Losses during Irrigation of Liquid Animal Manure. Sustainability 11(21), 6168; https://doi. org/10.3390/su11216168.

The author is a professor and extension agricultural engineer at Clemson University.

Inspired to farm closer to nature

At Roche Grain Farms, adjustments made to current farming practices lead to a more regenerative future.

“Diversity is key” when it comes to cover crop mixes, according to Kevin Roche of Roche Grain Farms.

All photos: Abby Bauer

by Abby Bauer, Managing Editor

Farming is nothing new for the Roche family, who has been raising livestock and growing crops at their farm in southeastern Wisconsin for 170 years. What has changed in recent years, though, is the family’s focus on regenerative agriculture. Over time, their goals for farming have become more centered on working in harmony with nature — rather than against it — to improve the soil on their fields.

Three of the six Roche brothers — Kevin, David, and Dennis — followed in the footsteps of their father and uncle when they took over the family business. Today, the farm is owned as an equal partnership between the trio and their wives, Tracy, Amy, and Jacki. Their father is still involved with the farm, and at the age of 85, one of his main jobs is installing drain tile in their fields.

All three brothers attended the University of Wisconsin-River Falls. Kevin returned home first after graduation to start his farming career with his father. David worked in landscaping for a few years, but when the opportunity arose to buy into the farm, he returned as well. Dennis served in the Navy before attending college, then came back to the family business.

The former dairy farm transitioned to beef cattle production decades ago, and in 1972, feedlot facilities were built on the farm. Today, the Roches finish about 1,200 head of Holstein steers, dairy and beef crossbreds, and beef steers annually. Cattle arrive at the farm in groups of 110 head between 400 and 700 pounds and are finished in about 300 days. The steers are sold to a few different buyers depending on market preferences. David said they are always running projections and locking in prices to ensure the cattle business is making money.

The cattle are fed homegrown forages along with corn fines from the co-op and distillers grains. Five different rations are utilized depending on age of the cattle and their stage of growth. When the cattle arrive at the farm, they are vaccinated, implanted, and treated if needed. The best treatment they have found, though, is to keep the steers clean and well bedded, which helps ward off many issues.

Keeping fields under cover

The grain side of the operation includes 3,700 acres located within a 5-mile radius of the farm that are used to grow corn, soybeans, and wheat for cash cropping. They also grow corn for silage and rye that is harvested in the form of ryelage as a forage source for their cattle.

The introduction of rye as a cover crop is just one example of the steps the trio has taken to improve the health of their soils. A mix of cereal rye, vetch, and winter peas is planted following corn silage, grain corn, and soybean harvest. The rye is typically what survives through the winter and some of the

acres are harvested in the spring.

David said the best part of ryelage is that they can feed less corn to the cattle. The forage also provides different nutrients in the ration, and he said the cattle seem to prefer it over corn silage. Overall, they can include less energy in the ration, and as another bonus, they are getting two crops off the same field.

After wheat harvest, fields are planted with a cover crop mix of seven to eight species, including more legumes that provide additional nitrogen. “When it comes to cover crop seeds, diversity is key,” Kevin said. “Cost is a factor too; as with everything else, these costs continue to rise.” Some of their rye is harvested as grain and is

Dennis, David, and Kevin Roche own and operate Roche Grain Farms near Columbus in southeastern Wisconsin.

continued on following page >>>

used for seed.

A valuable source of information on cover crops and other soil-friendly practices has come from a farmer-led organization called the Dodge County Farmers for Healthy Soil and Water. Kevin was involved with the group initially, and David currently serves on the board of directors. “It has been really helpful working with this group,” David said.

It was a presentation at one of these meetings that really spurred their interest in soil health. Ray Archuleta, known as “The Soil Guy,” is a nationally known expert who talks about soil health and cover crops based on his experience of working over three decades for the National Resources Conservation Service. Archuleta’s comments motivated them to make changes to their more conventional farming practices.

The Roches were also inspired by Rick Clark, a crop and cattle farmer in Indiana who is on the forefront of regenerative farming. “He is ahead of where we are, and we are trying to emulate him,” David said.

Organic farming is appealing to the Roches, but the transition is not practical for them right now. The same is true for cattle grazing. However, they are trying to use as many organic practices as possible and are really focusing on regenerative agriculture.

The brothers have transitioned toward cover crops on 100% of their fields because they realize the benefits. Kevin said that cover crops have improved soil health. “The crops are more uniform from end-to-end now,” he said. They can also plant into wetter fields in the spring, even in their claytype soils, if the fields had a cover.

David noted that their soil is now home to plenty of worms, which he explained is a good indicator of soil health. He added that cover crops have also helped reduce erosion.

Corn and soybeans are planted into cover crops that can be up to knee high. For corn, they have found it works best to kill off the cover crop three days after planting. For soybeans, it is done one to two weeks after planting.

Since they have been using no till and cover crops, they have noticed other changes in their fields, too. For one, “The weed pressure is different,” said Kevin. The brothers said they are managing around a different set of weeds now.

The brothers noted that cover crops are only part of the equation, though. Pairing cover crops with no-till is important as to not destroy the biological activity in the soil.

Kevin said a lot of what they learned has been by trial and error, and David jumped in to say they have had plenty of failures, too. It’s all part of the learning process.

“No-till takes more management,” Kevin noted. “Tillage can cover up the symptoms for unhealthy soil. It’s like aspirin for a headache.”

Corn and soybeans are harvested and stored on the farm. The Roches’ bins have capacity for 450,000 bushels.

A ready nutrient source

The Roches have been cutting down on potash and phosphorus applications the last few years. That’s because past soil tests revealed that a lot of those nutrients were tied up in the soil, but with more biological activity underground, the nutrients are more available.

Some of the nutrients applied to the fields come in the form of manure from their beef cattle. Their housing systems provide both solid and liquid manure for application.

The young steers are housed in bedded-pack barns. A layer of wood chips is covered by cornstalks. Sheets of gypsum drywall are laid on top of the pack to reduce the smell and, because it ties up the ammonia, they feel the drywall keeps the steers healthier. The gypsum also contains ammonium and sulfur, which eventually provides nutrients to the land, the brothers noted.

The solid manure is hauled out of the barns and is put into windrows to be composted. The rows are turned more often in the beginning of the summer but less often as time goes on. They have found that they dry out too much if turned too often, which slows down the composting, so they have gone from turning them once a week to turning them every three weeks to conserve the moisture. They noted that the quality of the compost product at the end depends on the effort that is put into managing the windrows.

Kevin said in the fall, they apply 2.5 to 3 tons of compost per acre, which is a valuable soil amendment, but he emphasized that there’s more to improving soil health than just adding compost. “It’s a combination of compost, no-till, and cover crops,” he said. “You have to stop digging up the worms’ home.”

The older cattle are housed in a barn with rubber-covered slatted floors. When first considering the purchase of mats to cover the slats, the Roches ran a trial where half the pens had rubber- covered slats and half did not. The steers in the pens with the mats were lying down more and gained 0.25 pound

Steers are raised on bedded packs and then moved into a barn with a rubbercovered slatted floor.

more per day, they observed, so they soon added mats to the whole barn.

Manure is stored underground in an 8-foot deep pit, and a biological control product is added to the manure to help break it down. The liquid manure is hauled out and applied in spring, summer, and fall, before corn planting, after wheat, and after fall harvest.

David said liquid manure is always applied to cover crops or ground that is soon to be planted. “We want a crop to be there to take in those nutrients right away,” he explained.

Manure is tested prior to application, and soils are tested every three to four years, as scheduled in their nutrient management plan. “Manure is a great fertilizer,” the brothers agreed, and they try to get the most out of it by spreading it out over all their acres, ensuring that every field gets an application of manure every two or three years.

Growing crops and children

The farm is operated with family labor, plus two full-time employees that assist with all aspects of the farm. “We all work well together,” David noted.

While corn chopping is done by a custom harvester, they do their own combining and storage. On the original dairy farm site is now a machine shed. On another farm sit several grain bins with 450,000 bushels of storage. What is not used to feed their cattle is sold to local co-ops for grain or for ethanol. The addition of a new grain dryer this past summer will allow harvest to be completed more quickly, they noted.

The brothers’ favorite aspects of farming are seeing plants grow and recognizing the benefits of different practices. Kevin said he also appreciates the opportunity to work with his sons and daughters on the farm, and David agreed. “It’s a great way to raise a family,” he said

It is clear that at the core of their farming practices is family, which remains very important to all of them. Between the three brothers, they have 17 children. While none of their offspring are working on the farm full time yet, there is plenty of potential for the farm to carry on for another generation. With regenerative agricultural practices in place, the Roches hope the land will be in even better condition when that time comes. 

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