New study reveals hog manure boosts crude protein in forages as well as improves yields.

Pork producers have long known that hog manure is a great substitute for commercial fertilizer in crop production.

A new study at the University of Manitoba shows that applying hog manure on tame grass hay land and pastures is also a great way to increase forage yield and quality.

The three-year study found that forages treated with hog manure had up to 80% more crude protein than untreated fields, a surprisingly high advantage, says head researcher Kim Ominski, associate professor at the university's Department of Animal Science.

Perennial tame hay requires a lot of nutrients every year to achieve maximum productivity. Even alfalfa and other legumes, crops that can fix their own nitrogen, still require substantial amounts of phosphorus, potassium and sulfur. Fortunately, hog manure contains all the major plant nutrients and a number of essential micronutrients.

Commercial Fertilizer

Hog manure's value increases as the cost of commercial fertilizer rises — and fertilizer prices have skyrocketed in the last two years. In early August, the Canadian price for potash (K) was $525(US$) a metric tonne (2,200 lb.); nitrogen (N), urea granular fertilizer (46-0-0), was selling for $650/tonne during the spring 2008 planting on the Canadian prairies; and 12-51-0, granular phosphorus (P), reached a whopping $1,350/tonne.

Since all of these nutrients are found in large quantities in hog manure, producers will want to use it whenever possible. And, with land prices on the rise, the University of Manitoba study also suggests that utilizing hog manure as fertilizer could be a great way to increase hay land productivity without expanding your land base.

Better Pastures, Too

Treated pastures also showed a surprising three-fold improvement, in both carrying capacity and live weight gain, over the control pastures that received no manure during the grazing season (Figure 1.)

Pastures that received a yearly application of hog manure, containing 110 lb. of available nitrogen (N)/acre, showed an 80% increase in crude protein. “Unfertilized pastures had 8 or 9% (crude protein) vs. 16 or 17% in the (manure) fertilized pastures, which is pretty remarkable,” Ominski says.

The study looked at both harvesting and grazing (Table 1 & Table 2) as primary means of removing forage from the system. The research site was divided into three zones with three different treatments that included no manure; a single application of manure every spring; and a split, spring and fall application of manure (Table 3).

Research results revealed that the seasonal variability of the manure, single or multiple applications or timing of the application did not affect forage quality or yield. Quantity seemed to be the only variable.

Ominski says the dramatic results might have been due to the fact the test site was fairly nutrient deficient at the onset of the trial. It contained primarily grass-based forages and had less than 10% legumes. None of the zones had previously received any significant quantities of liquid hog manure. Manure was applied using a splash plate.

Best Management Practices

Manure nutrients monitored in soil, groundwater and pasture forage confirmed using liquid hog manure application is a valuable nutrient recycling practice. Sampling and analysis revealed excess phosphorus (P) stayed within the root zone and did not move beyond. There was no evidence of significant nitrate seepage into the groundwater. Only a minimal amount of salmonella and E. coli present in the manure transferred into the soil. None were found in the cattle that ate the forages.

Ominski recommends that hog manure be adequately agitated to prevent variability in nutrients. Grazing with good stock density will avoid reduction in quality associated with maturity.

Nutrient removal is more efficient with hay than pasture, but consider alternating between grazing and haying for optimum nutrient removal.

The second phase of the study will be key, Ominski indicates. Mario Tenuta will further study phosphorus movement, while Denis Krause will continue monitoring water quality.

The project was funded through a partnership between the University of Manitoba, several commodity groups and multiple levels of government and industry. It allowed researchers to develop a research/demonstration site to promote best management practices and address environmental concerns, including nutrient and pathogen movement as well as water quality issues.

See Associated Figure