Page 32 • Dairy Star • Saturday, June 11, 2022
www.extension.umn.edu/dairy
Considering use of manure in alfalfa By Melissa Wilson and Josh Gamble
University of Minnesota & United States Department of Agriculture
Growing perennials, like alfalfa, can have water quality benets while still producing a crop for cattle feed. Using manure during the alfalfa rotation is often avoided, leaving a smaller land-base for manure to be applied. New liquid manure application equipment plus the use of trafc-tolerant alfalfa varieties may reduce some of the negative aspects of manure application on a living crop like alfalfa. What we did Our goal was two-fold: evaluate a trafc tolerant variety of alfalfa for manure application and determine if the use of dairy manure, fertilizer or a combination of both throughout the three-year alfalfa growth cycle could be used to maximize growth and quality. We established two varieties of Roundup Ready alfalfa in the spring of 2021 at the University of Minnesota’s Rosemount Research and Outreach Center: Pioneer 54VR10-RR (high yielding, FD-4) and Ameristand 455TQRR (trafc tolerant, FD-4). Prior to establishment, we applied phosphorus and potassium sulfate fertilizer according to soil test needs or injected dairy manure slurry at about 3,000 gallons per acre to supply full P needs for the rst year (about 27 pounds of P2O5 per acre). Each set of treatments was replicated in large strips four times. We harvested the alfalfa twice in the rst year and sent samples for forage quality analysis. We also evaluated crown health of plants in each plot, took soil samples to evaluate nutrient uptake and carbon cycling, and monitored nitrate leaching at 4-foot depth below the alfalfa crop. What did we nd? We experienced a drought in the 2021 growing season in Rosemount, Minnesota, so yields were lower than expected. The conventional alfalfa (Pioneer 54VR10-RR) yielded 1.8 tons of dry matter per acre, which was higher than the 1.5 tons of dry matter per acre for the trafc tolerant variety (Ameristand 455TQ-RR). Across both varieties, manure applied preestablishment increased yield by about 8% over the plots where only P and K sulfate fertilizer were applied. Samples for forage quality have not been analyzed yet. As far as plant health, plants were dug by hand in early November prior to a killing frost and scored on a scale of 1 to 4. A rating of 1 meant the plant was healthy; it had a robust crown and large root. And, 4 meant the plant looked questionable for survival; there were few crown buds, and the plant had a small root. The percentage of healthy plants scoring a 1 or 2 was calculated for each treatment. Generally, the trafc-tolerant variety of alfalfa had a higher percentage of healthy plants (53%) than the conventional variety (46%). For the trafc tolerant variety, pre-establishment manure increased the percentage of healthy plants (57%) compared to fertilizer only (47%).
The manure treatment had no effect on the percentage of healthy plants for the conventional variety. This was a bit surprising and will be interesting to see if that plays a role in stand longevity and yield in upcoming years of the study. What is next? This past fall, we further divided the research strips into smaller sections to evaluate nutrient management practices. After the second cutting in late August, we applied dairy manure or left some plots for spring-applied P and K sulfate fertilizer. The intent was to supply enough P and K for the second-year alfalfa crop. The dairy manure was applied in several different ways to see which methods worked the best for stand longevity. These included broadcast, banded on the surface (15 inches apart) or shallow injection (about 4 inches deep and 30 inches apart). About 6,000 gallons per acre were applied with each method to supply about 76 pounds of P2O5 per acre. We’ll continue to monitor the alfalfa during the 2023 and 2024 growing seasons, applying nutrients the same way as this past fall in fall 2023. We’ll also continue monitoring soil nutrient and carbon cycling and nitrate leaching. Keep your eyes out for future updates. This work is supported by the United States Department of Agriculture Agricultural Research Service through cooperative research agreement number 58-5062-1-008 and the National Alfalfa and Forage Alliance.
Dana Adams, adam1744@umn.edu 320-204-2968
Brad Heins hein0106@umn.edu 320-589-1711
Joe Armstrong armst225@umn.edu 612.624.3610
Nathan Hulinsky huli0013@umn.edu 320-203-6104
Luciano Caixeta lcaixeta@umn.edu 612-625-3130
Kevin Janni kjanni@umn.edu 612-625-3108
Gerard Cramer gcramer@umn.edu 612-625-8184
Karen Johnson ande9495@umn.edu 320-484-4334
Marcia Endres miendres@umn.edu 612-624-5391
Emily Krekelberg krek0033@umn.edu 507-280-2863
Joleen Hadrich jhadrich@umn.edu 612-626-5620
Claire LaCanne lacanne@umn.edu 507-332-6109
Les Hansen hanse009@umn.edu 612-624-2277
Brenda Miller nels4220@umn.edu 320-732-4435
Erin Royster royster@umn.edu Isaac Salfer ijsalfer@umn.edu 320-296-1357 Jim Salfer salfe001@umn.edu 320-203-6093 Mike Schutz mschutz@umn.edu 612-624-1205 Emma Severns sever575@umn.edu 507-934-7828 Melissa Wison mlw@umn.edu 612-625-4276
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