By John Yost
If you threw a couple darts at a map of the U.S., the weather experienced by each of those locations has probably been drastically different, regardless of how good you are at throwing darts.
If I were to take a 100-mile drive from my home in northeast Ohio, I could encounter areas that are in drought conditions, or I could go a different direction and be in an area that has been plagued by excessive rain through this growing season.
Everyone will have their opinion on which situation is worst, but as agriculture producers, we learn to manage whatever situation we find ourselves in and always look to the future.
For those of us who are grazers and hay producers, the summer months are the perfect time to begin planning for management of our forages this fall and into next spring: What fertility adjustments do you need to make, are you planning to renovate/reseed a field; do you intend to stockpile forage for late fall/winter grazing; or when will you make the last forage harvest of the season? The future productivity of your forage stands always starts with a well-managed fertility program.
Soil analysis
The summer months can be a great time to pull soil cores for analysis. Although the laboratory analysis of soil nutrients is a proven scientific process, you can introduce error with your sampling technique.
We are going to use our sample results to make decisions that impact multiple acres based on the analysis of a few ounces of soil. Where you collect the sample, the soil moisture at the time of sampling and the depth of sample collect can all affect the results.
The two factors that you have the most control over are your sampling location and sampling depth.
Sample location
There is a lot of technology that we can incorporate to increase our precision when selecting our sample locations. Soil maps can be downloaded from the U.S. Department of Agriculture NRCS Web Soil Survey (websoilsurvey.nrcs.usda.gov) which can be used in conjunction with GPS systems to identify management zones and locator points for pulling samples.
If you are not a technology type of person, you can easily identify those areas where there are topography differences or those areas that are frequented by livestock (shaded areas or locations around waterers, feed bunks and hay rings).
The more technology you can incorporate can increase your accuracy in sample collection and decrease the number of soil cores that you need to collect for a given zone. If you don’t have access to these technologies, you can overcome this by simply collecting more cores for each area.
Sample collection
Once you have identified your management zones, it is time to collect the samples. It is recommended that one combined sample represent no more than 25 acres. You can walk a zig-zag pattern, stopping every 50 to 100 feet to collect a core or drive to your sampling point and take four cores from the corners of your vehicle.
You should plan to collect 10 to 15 core samples from each management area. These cores can be combined in a bucket and a sample pulled to submit to the laboratory for testing. You will want to sample the top 8 inches, removing the soil surface portion of the sample, for soil nutrients and the top 3 to 4 inches for soil pH only.
Review results
Before you consider any fertilizer applications, it will be important to review your test results to determine if a soil pH adjustment is required. Each soil nutrient has a pH range where it is most available. The sweet spot for most of our micro and macronutrients is around 6.5.
If your forage composition is mainly grasses, you will be able to tolerate values closer to a pH of 6, and as your legume content increases your desired pH level should be closer to a pH of 6.7. Once pH increases to a 7.0, or greater, the availability of soil nutrients decreases.
Grazing management
You can do a lot to limit your need for added fertility through your grazing management. On average, an animal will only utilize about 20% of the nutrients they consume. The rest is excreted in urine and manure or dissipated from the production of heat.
Management-intensive grazing principles allow you to influence the animal’s behavior to help more uniformly redistribute those nutrients back to the pasture.
It is estimated that in a continuous grazing system, at low stocking density, it could take up to 27 years for grazing animals to deposit one manure pile in every one square yard of pasture. As you increase stocking density and rotation frequency, you can reduce this time to as little as two years when rotations are made every other day.
Application timing
If you do need to make fertility and pH adjustments, applications can be made anytime from early August through the last harvest. The last harvest should be conducted early enough to allow sufficient regrowth, which will allow the plants time to increase their energy reserves for overwintering and new spring growth.
If you have a stockpiled pasture, you want to begin grazing after the forage has gone dormant to reserve that energy for future regrowth.
I would be remiss if I didn’t remind you to also submit a manure sample for analysis if that will be the base of your fertility applications. Just as precision is necessary for your soil sampling, an equal level of precision will be important for a representative sample of your manure stockpiles.
(John Yost is an extension educator, Agriculture and Natural Resources, at Ohio State University College of Food, Agricultural and Environmental Sciences / OSU Extension-Wayne County. He can be reached at 330-264-8722 or yost.77@osu.edu.)
