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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Research Project #440061

Research Project: Evaluating Best Management Practices for Manure Application into Alfalfa to Optimize Yield and Environmental Outcomes

Location: Plant Science Research

Project Number: 5062-21500-001-007-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Apr 1, 2021
End Date: Mar 31, 2026

1. Evaluate manure application timing and method in alfalfa and its impacts on yield and forage quality compared with traditional commercial fertilization practices. 2. Develop best management practices to be disseminated to Minnesota alfalfa producers.

A glyphosate-resistant ready alfalfa variety with appropriate winter hardiness and fall-dormancy ratings for the region will be chosen. The experiment will be set up as a strip trial with plots that are 10 by 100 feet long. Liquid dairy manure will be transported from a local dairy operation each year and stored in large poly tanks until application. Manure will be applied with a 1,500 gallon plot-sized manure tank system with flow rate control to ensure accurate rates are applied. Manure samples will be collected and sent for analysis prior to application to calculate appropriate application rates. Samples will also be collected on the day of application to better understand the as-applied nutrient levels. The experimental design will be randomized complete blocks with each block replicated three times. Ten treatments will include a combination of manure timing (prior to establishment, annually after last summer cutting, or the combination of the two) and application method after the alfalfa is established. Prior to establishment, manure will be injected at a phosphorus-based application rate. In plots where manure is not applied prior to establishment, commercial fertilizers will be used to supply P, K, and S needs of the crop. Application methods after establishment for the manure will include surface broadcast; surface banding; and shallow, minimal-disturbance injection. These will be compared to fall-applied fertilizer applications (as needed according to soil tests), and a no-additional nutrients control. As with the pre-establishment treatments, manure will be applied at a P-based rate after the last summer cutting to avoid phosphorus buildup in the soil. By including combinations of when manure is applied in the alfalfa rotation, we can determine the best management practices to include in future outreach materials. We will measure alfalfa yield and quality; stand counts; soil compaction; soil carbon, nitrogen and phosphorus cycling; ammonia gas losses after manure application; and nitrate leaching. These will allow us to evaluate the agronomic as well as the environmental aspects of this crop production system. Alfalfa will be sampled by hand to a stubble height of 5 cm in two 0.5-m2 quadrats per plot for drymatter (DM) and forage quality determination. A flail-type forage harvester will be used to harvest a 0.9× 6.1 m area of each plot to a height of 5-cm. Dry matter yield of each plot will be calculated based on the fresh forage weight, area harvested, and percentage DM. Alfalfa will be harvested at two to three cuttings in year 1 (establishment year) and four cuttings in year 2. Samples will be sent to a commercial laboratory for forage quality analysis, including nutrients, crude protein, acid detergent fiber (ADF), neutral detergent fiber (NDF), etc. Soil compaction (using a soil penetrometer) and stand counts will be measured every spring to see if these are potential factors impacting yield or quality after manure application.