Out With the Old, In with the Manure

Spread the word: There’s power in manure.

Thanks to research, the pork sector is constantly evolving, finding new ways to address a range of issues. As a prime example, scientists are studying the potential for manure to benefit production, profits and the environment. Since these are all priorities for Swine Innovation Porc (SIP), they were pleased to fund the project “Science-Based Application of Various Forms of Swine Manure to Improve the Environment and Production Sustainability while Maximizing Nutrient Use Efficiency and Farming Profitability”. Given the progress so far, it is money well spent.

“Swine manure is an excellent source of nutrients that are essential to crop production, while also offering cost savings compared to synthetic fertilizers” says Dr. Tiequan Zhang, senior research scientist with Agriculture & Agri-Food Canada (AAFC). “Nitrogen (N) is one of the multiple essential nutrients contained in manure, in both mineral and organic forms.”

In mineral form, N is readily available to crops in the year it is used. The organic form of N needs to be broken down into mineral N before being applied to crops, and one year of manure application can provide crops with N for multiple growing seasons. In order to maximize crop yield in an environmentally sustainable manner, however, scientists must determine the legacy value of the N, a key focus of this study. Legacy values in fertilization refer to the long-term effects of fertilization practices on soil nutrient availability.

“To determine those values, we conducted greenhouse studies using soils from fields that have been treated with liquid and solid swine manures over 19 years. We then compared the results with soils receiving synthetic fertilizers over the same time frame.”

Using a corn-soybean rotation, broadcast application of manure or synthetic fertilizer was made to the corn phase of the rotation, with residual nutrients picked up by the soybeans.

“In this case, we found that long-term pig manure applications generated significant residual N impacts on crop growth over a growing season. As a result, added fertilizer nitrogen rates could be markedly reduced at the same yield level, leading to substantial savings in fertilizer costs. However, it is worth noting that the results are preliminary and obtained under greenhouse conditions, so they need to be validated and calibrated in the field.”

Relative to synthetic fertilizer, soils receiving pig manure showed higher soil organic carbon, improved soil aggregate stability and better soil health. Together, these enhancements produced a 19% increase in crop yield potential.

“We were encouraged to see that N losses were less in soils with swine manure than those with synthetic fertilizer. The N loss reduction with swine manures were 56-78% over the non-growing season. Those soil nitrogen losses would have happened to the air through denitrification or to the water through leaching.”

Denitrification is a microbial process that converts nitrate into nitrogen gases. This process removes bioavailable nitrogen and returns it to the atmosphere. Nitrate leaching occurs when excess water carries nitrates through soil into groundwater, posing potential health risks to humans.

By replacing chemical fertilizer with swine manure, the industry could produce significant environmental benefits through reduced greenhouse gas emissions and improved water quality.

As producers strive for financial sustainability in a highly competitive business, this project is a prime example of knowledge unlocking efficiencies. In an industry where costs continue to rise, fertilizer is a major expense in crop production, so alternatives like swine manure that promise savings are worth their weight in gold.

“In seeking to enhance producer profits from crop production, a key aspect is maximizing the benefits of both swine manure and chemical fertilizers. Through 4R recommendations, we can optimize the use of swine manure and chemical fertilizer and better match nitrogen and phosphorus levels to crop needs.”

The 4R Nutrient Stewardship framework is designed to enhance nutrient management in agriculture while considering economic, environmental, and social factors. The four principles are right source, right rate, right time and right place.

Those recommendations play a critical role for the environment as well. By avoiding over-fertilization and lowering nutrient loss to the air and water, growers can reduce environmental harm and make their operations even greener.

As this study demonstrates, the benefits of swine manure as an alternative to synthetic fertilizers are many and varied. Of course, for change to occur, producers and industry must be aware of manure’s potential, so researchers are seeking to spread the word. In the process, they hope more growers will consider foregoing synthetic fertilizer in favor of more efficient, affordable and eco-friendly manure.

“Moving forward with this project, we are continuing to identify the maximum economic fertilizer rate in soils that previously received swine manures, as well as the true fertilizer values of swine manure nitrogen in the season of application and over the long-term.”