Traditionally, hog producers managed their supply of on farm organic fertiliser by utilising a nitrogen (N) based approach which matched the relative nitrogen value of organic fertiliser to the nitrogen requirements of whatever crops are being grown. Due to the long-term focus on soil and crop requirements for nitrogen only, phosphorus (P) levels in soil have led to increasing concerns about ground water quality. As a result, many provincial and state regulators across North America, including Manitoba, are exploring or have already implemented changes which will shift to a phosphorus-based approach.

These changes mean hog producers will need to re-evaluate their organic fertiliser management programmes in order to comply with the new regulations. The province of Manitoba, which is home to the third largest pig herd in Canada, will fully move to a phosphorus-based approach for hog-sourced organic fertiliser in November 2013.

While hog producers will continue to be able to somewhat manage on farm organic fertiliser under these new regulations via hog diet changes (use of phytase enzyme), cropping decisions (adding spring or winter wheat to the rotation) and land activities (sowing on fallow ground or into stubble depending on soil type and cropping choices in order to maximise phosphorus usage), other approaches may deliver more flexibility and value.

One such approach involves separating the phosphorus-rich solids contained in hog-sourced organic fertiliser and composting them prior to application. At NCLE’s Agricultural By-products Processing Research and Demonstration Facility, researchers are looking at innovative means of processing hog-sourced organic fertiliser to find suitable options for managing organic fertiliser phosphorus and to improve the value of the processed material while ensuring environmental sustainability.

Jolene Rutter, MSc candidate at the University of Manitoba, is evaluating the value of using a centrifuge-type separator together with composting to achieve high levels of both solids separation and phosphorus capture.

Ms Rutter explained: “Composting the solids stabilizes the nitrogen instead of losing it to the atmosphere through volatilisation. Stabilisation of the nutrients also makes it is easier to store until it is needed and can be applied to maintain long-term soil fertility,”

Centrifugation separation also concentrates more of the phosphorus from the original liquid into the solids allowing for more economical options for hauling and spreading the composted fertiliser.

Centrifugation technology for the purposes of separating liquid organic fertiliser is widely used in Quebec - home to Canada’s largest number of pigs - where acreage is limited and regulations for its use are stringent. Additional benefits to applying the composted material include improved soil fertility, and increased microbial diversity, moisture-holding capacity and soil organic matter levels.

A key component of the composting process involves developing the best carbon to nitrogen (or C:N) ratio. Ms Rutter’s research is exploring the relationship between which carbon sources (i.e. wheat straw or wood shavings) provide the best environment by which the solids will be most effectively broken down and nitrogen-value of the fertiliser is conserved.

Her research is part of an ongoing project at the NCLE but findings to this point have been presented at Manitoba Hog and Poultry Days as well as the most recent ‘Waste to Worth’ conference hosted by the Livestock and Poultry Environmental Learning Center in Denver, Colorado.

The National Center of Livestock and the Environment (NCLE) utilises Genesus Genetics in all its Swine Research Projects.

June 2013