Flourishing Fields
Welcome to the first post in Flourishing Fields, our new blog series on effective pasture management. Each installment we will share practical knowledge and expert tips on how to manage your farm to produce the flourishing fields that in turn nourish thriving ruminant livestock.
If you attended our presentation at the recent New Jersey Agricultural Convention, you already got a taste for what we’ll examine in this series. Future installments will cover such topics as flexible infrastructure for moving animals, adapting rotation patterns, smart ways to minimize bare soil, seeding specific plant species in your pasture, and more. But first, we’ll start where your pasture itself starts: the soil.
Understanding your soils
A flourishing pasture and its soil are interdependent. Properly functioning soils capture, store, and redistribute water; grow plants; and cycle plant nutrients. Identifying and learning about your field’s soil type—or types—is an important place to begin understanding your field’s limitations and possibilities. USDA’s Web Soil Survey (WSS) (websoilsurvey.org) provides free interactive access to soil information for all our fields. A little orientation to this tool is useful, and several video tutorials are available to help you navigate. This 11-minute video tutorial from American Farmland Trust is a good resource that can help you get started.
Once you identify the soil types in your fields, the detailed descriptions will help you understand the drainage characteristics, restrictive layers, composition and parent material, all factors that will affect plant composition and potential productivity. Bear in mind, one flourishing field will look different from another, depending on their underlying soil types.
Next, you can take your knowledge and planning a step further with the Web Soil Survey, by calculating your expected annual averages of forage production per acre for those various soils. Here’s how: Once you have your soils mapped, click on the Soil Data Explorer tab. Under the dropdown menu for Suitabilities and Limitations Ratings> Vegetative Productivity> Non-Irrigated Capability Class (Component). Under Basic Options, check “pasture” and “View Rating” to see the expected average productivity for that soil, under high management conditions.
The average yields are rated via Animal Units per Month (AUMs). This refers to the average number of 1,000-pound ruminant animals that could be maintained on pasture of that soil type for one month. At a minimum, it’s helpful to know the relative range of production for different fields of your farm, or even within the same field. To begin determining stocking rates: 1. Calculate the total AUMs available for each soil type by multiplying the acreage of each soil type by its AUM rating. 2. Total the AUMs calculated for each soil type to arrive at the total AUMs available for your entire Area of Interest. 3. Divide the total AUMs by the number of months you intend to graze, to determine the total number of Animal Units (AUs) your pasture could support, with a high level of management.
Equations:
Total Animal Units per Month (AUM) for each soil type
= Acreage of soil type * AUM (or the average number of 1,000-pound ruminants that can be maintained on pasture for that soil type for one month)
Total AUMs for entire Area of Interest (AOI) = Add up AUMs for each soil type
Total Animal Units (AU) that your AOI can support
= Total AUMs for entire AOI / Number of months grazing = Stocking Rate
Example:
To determine stocking rate from the example above, multiply each soil type Rating (AUMs) by the Acres in AOI. The total of these are 23.78, 6.97 and 1.08.
Adding these together gives us a total of 31.83 AUMs for the entire 6.6 acres.
Next divide the total AUMs by the planned number of grazing months. If we plan to graze this example field for 8 months, we could stock 3.98 AUs, or 3,980 pounds of animal for that time period. If we plan for 7 months, then 4.55 AUs. These stocking rates assume high management of the field and do not account for annual forage growth variations due to unusual weather. They also don’t necessarily match natural growth curves of plants with dry matter needs of a specific class of animals at a particular time or selective grazing. But they do provide a good starting point to better understand a field’s potential productivity.
The next step to understanding your soils is soil testing. Gather soil samples to assess the pH, organic matter, phosphorus and potassium levels of the soil along with their cation exchange capacity. Understanding these levels can provide a current snapshot of a field, including how recent management decisions may have affected the field’s fertility. This video from Rutgers provides a helpful tutorial on soil sampling.
If limited land availability has you looking to maximize production and corresponding stocking densities of animals, I encourage you to amend your soil as recommended by the soil lab. Optimum pH, potassium and phosphorus levels will allow the grasses, forbs (broad-leafed plants) and legumes in your fields to maximize their potential by promoting root development, facilitating water transport within the plants, and increasing stress tolerance and growth. When applying amendments, be sure that the soil conditions are dry enough that the heavy equipment won’t create unnecessary compaction. Also, time spreading to minimize any potential run-off of amendments.
I’ve known some farmers who never amended their less-than-ideal soils and had healthy fields. But that typically takes excellent pasture management with frequent animal rotations, initial lower stocking rates and an abundance of time.
While amending phosphorus and potassium can help the soil reach its potential, the soil lab may also recommend applying nitrogen, which can be expensive. Consider alternatives. Though the productivity of hay fields with no grazing animals may benefit from nitrogen applications, adding legumes to pastures and properly rotationally grazing animals can more sustainably make nitrogen available for the plants in your pastures.
Even adding large tap-rooted annual brassicas, such as forage radish, can make a good amount of nitrogen available as they decompose. Because of its fleeting nature and ability to be supplied in more sustainable ways, I'm not a big proponent of spreading nitrogen on pastures.
With some time, attention, and use of available tools, understanding your soil can unlock potential in your planning and management, ultimately leading to flourishing fields, thriving livestock animals, and notably increased results.
Feel free to reach out with feedback or questions—we’re here to help!
Craig Haney
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