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How to put together a manure management plan

3 pictures in a collage; student workers collecting soil samples; a computer-generated zone map; a student worker mixing manure in a concrete tank

By: Melissa Wilson, Extension specialist; Nancy Bohl Bormann, Researcher; & Chryseis Modderman, Extension educator

It’s that time of year when the crops are coming off the field and folks are starting to think about next year’s crop. If you have livestock on your farm, you are also thinking about manure application, which may happen this fall and/or next spring. How can you maximize use of your manure and minimize how much fertilizer you have to purchase?

A manure management plan can help you look at the big picture. Remember, manure is like a multivitamin for your field – it has all the nutrients that crops need, just not necessarily in the right amounts! Just like multivitamins for people, you don’t want to overdo it. So, what information do you need for a manure management plan?

Manure

There are two things you need to know about your manure – how much do you have and what’s in it? If this will be the first year that you apply manure from a new operation, you’ll have to estimate this information. The American Society for Agricultural and Biosystems Engineers (ASABE) or the Midwest Plan Service have some methods for doing that. To find some estimates of the nutrient content, you can visit the University of Minnesota’s Manure Database (called ManureDB) to look up the range of nutrients you can expect for different manure types.

If you have an existing operation, you will want to use your records for the past three to five years and find the average manure volume and nutrient contents. Having data from your operation is always best as it reflects what you do on your farm.

Don’t forget to get manure samples collected when you apply it this year and send them to a lab! Contact your preferred lab prior to sampling to check if they offer sample containers. Visit the UMN Manure Management YouTube page for videos on how to sample liquid and solid manures. This list has labs that are certified by the Minnesota Department of Agriculture’s Manure Analysis Proficiency Program. Having current manure samples will keep your records up to date for future years.

Crops

In thinking about nutrient management for your farm, you will need to know what fields and crops you have to work with. Start by collecting field maps (electronic or paper maps are fine) and mark out sensitive features, like streams, ditches, wetlands, wells, sinkholes, open-tile inlets, etc. Next, highlight the setbacks from these sensitive areas where manure cannot be applied according to state rules. The Minnesota Pollution Control Agency just released an online interactive map to help with this task. Once this is done, you can determine the acreage for each field where manure can be applied.

Next, you will need to know the crop rotation for each field. This includes the past two years and the upcoming year. Finally, was manure applied in any of your fields for last year’s crop? Make note of the rate that was applied so that you can calculate second year nitrogen (N) credits. It may be helpful to make a list of each field, the number of acres manure can be applied to, the crop rotation, and whether a second year N credit needs to be calculated. This will help you organize your plan.

Soil

Getting your soil tested regularly in each field is critical to get the best bang for your buck from manure. Fields that test lower in phosphorus (P) and potassium (K) can use the full range of nutrients in manure better than fields that already have high or very high levels of P and K. At a minimum, get your soils tested every three to five years. If manure is applied more frequently to these fields, you may want to sample more frequently. For a review of manure N-P-K recommendations, you can view the UMN Extension guidelines for manure application rates online.

Getting a plan in place

The main goal of a manure management plan is to have enough fields to apply all of your manure to in an agronomically- and environmentally-sound manner. Remember that manure has added benefits over commercial fertilizers – it often provides organic matter and micronutrients. If you have more fields than manure, you can be strategic about distributing the nutrients so that more fields get these benefits, even if it means applying lower rates. If you have fewer fields than manure, you can arrange for whatever you cannot use to be transferred to neighbors that can use it.

There are some general strategies for thinking about which fields to prioritize when it comes to manure application.

First, consider whether you want to apply an N-based rate or a P-based rate. The N-based rate is likely the highest application rate you can potentially use and will supply all N-needs of the crop (you will need to subtract out any second-year manure N credits, starter N fertilizer, or other N sources from crop needs). It may supply more P and K than the crop needs for this year, though. Depending on your crop rotation and how often you apply manure, soil test P levels may build over time, so this will need to be monitored. If you have fields that already have sufficient P and K soil test levels and you want to avoid building these levels any higher, choosing a P-based application rate for your manure could be beneficial. Any additional N that’s needed could then be applied with commercial fertilizer prior to planting or as a sidedress. 

This strategy helps to balance out the nutrient needs of the crop while minimizing the chance of raising soil test P levels if they are already high or very high. The main thing to remember is that all N sources that will be applied to a field need to be considered when using manure. In Minnesota, you cannot apply more N than is needed by the crop in any growing season where manure is being applied.

There are other considerations as well, including distance to each field and the economics of hauling it to various locations, field conditions, weather, odor, neighbor relations, etc. These all can be considered in your manure management plan. The one main thing to remember, however, is that this is just a plan. It is good to have flexibility built in so that changing weather conditions or other unforeseen circumstances can be managed. Make sure to keep records of what actually happened so that you can incorporate that into next year’s plan.

For more details on manure management planning, check out the Minnesota Pollution Control Agency’s webpage on land application of manure. Our manure team at the University of Minnesota is also working on an online course that covers manure management planning and the science behind it. Keep an eye out for that over the next winter on Extension’s manure management website!

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