Livestock manure is known to provide valuable nutrients to the soil. And, if managed correctly, it can also provide additional benefits by improving the soil’s biological, chemical and physical properties.
How livestock manure affects soil health
Manure is composed of four main components: carbon, nutrients, microbial life, and water.
Livestock manure is mainly composed of carbon compounds that have been broken down by the animals’ digestive tracts. Carbon that is incorporated into the soil profile improves many soil health indicators, such as water holding capacity, nutrient cycling, and raising and/or buffering soil pH.
While many plants and animals can survive at different ranges of pH, it is still important to maintain soil pH values between 6-8 so that soil nutrients are available. Manure has been found to have a liming and buffering effect, which can benefit crops growing in acidic soils.
Manure in the soil also increases the cation exchange capacity, which affects soil’s ability to hold onto available nutrients. Increasing soil carbon through manure adds available sites in the soil where nutrients can bind and be made available to crops throughout the growing season. This increases nutrients in the soil; though, it’s important to note, not all nutrients found in manure are immediately available and some may need to be broken down by microbes or chemical transformation in order to be taken up by plants.
Most importantly, manure is an important part of recycling nutrients. Livestock that eat and digest the grain or leaf tissues are removing nutrients from the soil. When that manure is applied to the soil, many of those nutrients are returned. This increases soil biological activity by introducing new and important microorganisms from manure, as well as animal saliva while the animal is grazing. Nutrients from manure (when applied correctly) can also mean growers are spending less money on commercial fertilizers.
How to assess the value of manure to your soil
- Get your manure tested. Nutrient values differ between species, as well as where it’s pulled from in the lagoon or pile. Most universities or state organizations have manure recommendations for this information.
- Estimate the cost of commercial fertilizer and compare it to the amount of micro- and macronutrients you applied to your soils. Remember, most manure nutrients are not immediately available in the first year and so it will benefit you for up to two years after application!
- Calculate rates of removal from row crops to know how much manure you need to apply, as well as to know whether you are applying for N or P needs (this is state-specific). Always follow state and local legislation around manure management.
- Avoid high-risk areas that may impact groundwater or wetlands. We want to improve soil health, but not at the cost of harming other systems.
- Incorporation of manure prevents N volatilization (gaseous losses), which gives you more N available for crops but can impact soil aggregation. There is new and existing research looking at what is the best method of application for manure – whether injected, incorporated, or broadcasted – so be sure to do your homework and consider your farm’s available resources (e.g., equipment) to determine the best approach.