Features Agronomy Fertility and Nutrients
Livestock manure can help reduce fertilizer costs

Manure is even more valuable as a fertilizer replacement.  Photo courtesy of Rick Taillieu.

Nitrogen (N) and phosphate (P) fertilizer prices have taken a roller-coaster ride during the past few years. The spike in prices had many farmers scrambling to figure out the best fertility plans, and how to get the best bang for their buck. For some, livestock manure is a key part of the equation. “Typically, crop farmers are willing to pay for compost, but get fresh manure for free,” explains research scientist Frank Larney with Agriculture and Agri-Food Canada at Lethbridge, Alberta. “But with fertilizer prices increasing, what does that do in terms of using manure to replace some of those fertilizer inputs?”

In the 2006 Census (compared to 1981), eight out of the top 10 regions in Canada that experienced an increase in manure production were in Alberta (mostly beef production), with the other two in Manitoba (hog production). On average, feedlots produce two tonnes of manure per head per year. For farmers in these areas, manure can be a viable option as a replacement for fertilizer.

The main difficulty for crop farmers purchasing manure is establishing a price for it. Basing the price for manure on the replacement value of N and P in the manure is one method. And to do that, a grower needs to know the N and P content of his manure, which requires a laboratory analysis. There are also extra benefits to manure beyond N and P due to its soil-building qualities.

Larney looked at the price of N and P fertilizer to assess how that would affect the value of manure. He used average values for nutrient content from four southern Alberta feedlots. In the two-year period from October 2006 to October 2008, the value of N and P in manure almost tripled from $12 to $35. The manure values were adjusted to 50 percent moisture content and no credit was given to other nutrients in manure, such as potassium (K) or to organic matter.

The high price of P, compared to N, makes the manure P more valuable than manure N. While fertilizer prices have moderated somewhat from the highs of October 2008, the valuation exercise is worthwhile in helping to illustrate how changing fertilizer prices can change the value of manure.

Addressing N:P ratios
One of the challenges in using manure as fertilizer is that the N:P ratio in manure does not match crop needs. Most agricultural crops have an N:P ratio of around 4.5 to 6, using 4.5 to 6 times more N than P.  Livestock manure, though, has an N:P ratio around 2.5 to 3.5:1. Applying manure to meet crop N needs means P is over-applied, and eventually, surface soil level P will increase and has the potential to cause water contamination. 

Today, some farmers are applying manure to meet crop P needs, and then topping up N fertility with fertilizer. A common strategy is to apply P at three times the annual P rate once every three years. For example, applying manure to supply 22 kg of P per hectare (20 lbs of P per acre) would apply approximately 50 kg of N per hectare (45 lbs of N per acre) of which 25 kg of N per hectare (22 lbs of N per acre) is available in the year of application. The remaining crop N needs would be met with fertilizer N, according to soil test recommendations.

Manure also varies in the amount of nutrients available in the year of application, depending on manure type, age of manure and storage. For fresh manure, about 25 percent of the N is available at application and another 25 percent release in the first year. For P, roughly 60 to 70 percent is available at application and another 20 to 30 percent available during the year, for a rough total of about 90 percent availability in the year of application. “N and P are generally more available from fresh manure in the year of application. If it is stockpiled, less is available, and if it is composted, then N and P are further stabilized and less available compared to fresh manure,” explains Larney.

Marketing and trading manure
Trevor Wallace, nutrient management specialist with Alberta Agriculture and Rural Development (ARD) at Red Deer, says that one of the difficulties in using manure as a nutrient source is pricing the product beyond the basic value of N and P. “There are two ways to value manure. One is the value if you use it yourself, and the other is the value if the manure is bought or sold,” he says. 

The difficulty in establishing that value, though, is that there is not a formal marketing system in place, and manure is not formally traded as a commodity like fertilizer. Compounding the problem is that manure’s low nutrient content means that at some point, hauling manure does not make economic sense.

To help address these problems, ARD has developed several web-based services on “Ropin’ the Web.” The first is a Manure and Compost Directory, where buyers and sellers can list their manure for sale or as “wanted.”

“Once people are trading a product, it becomes a commodity and there is price determination mechanism,” explains Wallace.

For crop farmers who may not have the equipment to haul or apply manure, ARD also has a “Manure and Compost Custom Applicators” directory on its website. Here custom applicators can advertise their services and producers can find service providers to apply manure.

Another service that ARD is working on is a Manure Transportation Calculator. It is currently at the testing stage, and uses an Excel spreadsheet that factors in the value of manure nutrients being used from an application and subtracts the manure application costs. “We hope to show the real value of manure, beyond the basic nutrient value less the transportation costs. For example, fields further away from the feedlot that have never received manure may receive greater value from manure than fields closer to the feedlot that routinely receive manure,” explains Wallace.