SWINE&U

The nutrient story from Melissa Wilson

As one part of the larger study, we’re growing hybrid rye using swine manure as the primary nutrient source.

SWINE & U

By Diane DeWitte

In the first year of the study, the use of liquid swine manure tended to produce higher grain yields than solid or composted swine manure

Application rates of 60 to 120 pounds per acre of first year available nitrogen optimized yield without significantly over-applying phosphorus and potassium.

Hybrid rye grain and straw produced for the larger study will be tested as an alternative feed and bedding source for organic swine production

Hybrid rye is being grown in Minnesota as an alternative to traditional winter rye varieties. In organic production systems, the grain may be used as an alternative feed for livestock while the straw can be used for bedding. A new research project is evaluating hybrid rye for swine production, so we wanted to know if various types of swine manure (liquid, solid, or composted) could be used as a primary nutrient source.

In fall 2021, we started a field trial at the WCROC. We applied five different rates of each type of manure in early September to supply zero to 240 pounds of first-year available nitrogen per acre. We assumed 75 percent of the total nitrogen would be available the first year for the liquid and solid swine manure and 40 percent would be available from the composted swine manure. After application, we incorporated the manure within 12 hours and planted hybrid rye within the next few days. The following summer, we harvested the rye and analyzed the grain for crude protein.

The first of this two-year study has been completed. We found that use of liquid swine manure resulted in the highest grain yield (around 100 bushels per acre) compared with solid and composted swine manure, which produced around 80 bushels per acre each at the highest application rates. Interestingly, the crude protein was not affected by nutrient source, suggesting that nitrogen may not have been the primary reason for the decreased yield with the solid and composted swine manure. In general, crude protein increased with increasing application rate, regardless of the nutrient source. Hybrid rye yield was not significantly increased when liquid swine manure was applied above 120 pounds of first-year available N per acre (about

5,000 gallons per acre). This is in line with fertilizer recommendations for conventionally managed hybrid rye (110-150 pounds of N per acre depending on previous crop). For solid and composted manure, yield was not significantly increased above 60 pounds of first year available nitrogen per acre (about 4 to 5 tons per acre). Higher rates improved yield slightly, but significantly overapplied phosphorus and potassium (anywhere from 60 to 400 pounds of phosphorus and 115 to 480 pounds of potassium!). When working with manure, there is always a balance between optimizing the use of nitrogen while preventing buildup of soil phosphorus to very high levels.

U of M Researcher Joel Tallaksen and Professor Bill Lazarus will be evaluating the economics and impacts of the entire system. Their goal is to see if integrating winter hybrid rye into pig production is viable for organic farmers and whether it can improve environmental outcomes by increasing crop diversity compared with a typical crop rotation. As far as the field trials, manure was applied again last fall in a new field and hybrid rye was planted. As the snow melts and temperatures rise, the team is anxious to determine if the winter of 2022-23 caused any stand loss.

Save the date

WCROC and the research team will host an Organic Swine and Dairy Field Day on June 22 at the Research and Outreach Center (46352 MN-329, Morris, Minn.). The event will be held from 9:00 a.m. to 1:00 p.m. Morning speakers will cover the details of substituting hybrid rye in a traditional corn-soy swine diet, feeding and grazing organic dairy cows, and more. Lunch will include pork loin from both the conventionally-fed pigs and the organic rye-fed pigs. After lunch attendees can take a pasture walk to evaluate the progress of the 2023 hybrid rye crop and the dairy graze.

The event is free of charge but RSVP is requested. Participants can register by calling the WROC at (320) 589-1711, or email Diane DeWitte at stouf002@umn.edu.

This project is supported by the Organic Agriculture Research and Extension Initiatives of the U.S. Department of Agriculture’s National Institute of Food and Agricultural.

Portions of this article were originally published in the Stevens County Times and has been republished here with permission. Melissa Wilson is the U of M Extension nutrient management specialist and can be reached at wilso984@umn.edu. Diane DeWitte is a U of M Extension swine educator who can be reached at stouf002@umn.edu. v