The past two winters we in Extension have been providing programs to get producers certified for Fertilizer Application. Individuals are encouraged to obtain certification as soon as possible. The certification must be obtained by Sept. 30, 2017.

Through the certification process, one of the topics we discuss is soil sampling. I have been somewhat surprised at the number of producers (not just Clinton County) that really don’t know how to take an effective soil sample and in turn, really do not understand what the soil test results mean to them.

I realize many producers rely on someone else to do the sampling and to interpret the results. With all the discussion of water quality and how agriculture impacts the waters of our state, I would encourage producers to get a better understanding of effective soil sampling, understanding the results, and managing their fertility programs more efficiently.

There are many different tools and approaches available that, if used correctly, can help to improve your nutrient management (variable rate application, precision placement, crop sensing via NDVI, late-season application, nutrient BMPs, etc.). However, selecting the correct tools and using them to your advantage is not always an easy process, since the best tool and the best approach can vary by farmer and field.

The key to a successful soil fertility program is to identify your goals and develop a plan to meet those goals each season. Identifying both short and long term goals make it possible to develop a strategy to use precision technologies to systematically improve your soil fertility program.

Ohio State University crop and soil specialists all agree on some goals you may consider:

1. Improve mapping of field variation that affects soil fertility.

2. Maximize the economic return of fertilizer applications.

3. Reduce off-site movement of nutrients.

According to Ohio State specialists, one of the most important decisions that you will make as part of your fertility program is how to divide (the area within a field boundary) a field into representative areas and what the area represents – yield, soil type etc.

Currently, there are two widely used methods: grid and zone sampling. Deciding between the two is not as simple as it may seem, since these methods require different sampling techniques, different analysis, and different applications. It is important to keep your fertility program goals in mind when making this decision.

Grid sampling involves taking samples at regular intervals across the landscape of a field. Grid size is selected to provide the desired data resolution. A 2.5-acre grid size is commonly used (360 by 360 feet); however, choosing a grid size that matches up to spreader equipment widths is recommended.

Smaller grids may be necessary to accurately capture differences in fields with a high degree of variation and it may be possible to increase grid size if a field is fairly uniform. Cost increases as the number of samples increase; however, research has shown that smaller grids provide higher resolution, and often more useful, data.

OSU suggests grid sampling should be used when there is little information available about the variation in nutrient levels across a field. Grid sampling may be useful in fields where variability is expected but the field history is not well known, topography is uniform but differences in soil type occur, varied management patterns have been used in the past or manure applications have occurred.

Proper grid sampling makes it possible to identify variation within a field and is an important data layer when determining future management zones for fertilizer applications.

Zone sampling involves dividing the field into zones that are uniform enough to be managed as a whole and then sampling to determine the average soil test values for those zones. The success of the zone sampling relies on the amount and quality of the data used to determine the zones.

Layers such as soils maps, aerial photos, yield maps, topographic maps, management history and personal field experience can provide valuable information about the variation in a field. This information can be used to define sample zones or management zones in a field. As the number of management zones in a field increase, the number of samples needed increase. If only a few zones exist, samples can be combined to reduce the cost of analytical expenses.

Management zones are a better choice than grids when the operator has a long history of working with the field, topography varies and can be used to define zones, where yield map data over time has defined high and low yielding areas, the soil type map represents yield zones or other remote sensing data is available to overlay with operator experience to define yield patterns in a field.

Remember sample area should represent no more than 25 acres for zone sampling.

It is important to note that differences in yield may not be always be caused by differences in soil test values. Identifying other yield limiting factors will help fine tune your soil fertility program for each field.

If you have already received your certification you are ahead of the game. For those producers yet to receive their Fertilizer Application certification, there will be meetings this winter to attend.

If you already hold a private applicator pesticide license and it will expire in 2017, your opportunity in Clinton County will be Jan. 19, 2017, at the Extension office community room for pesticide and fertilizer certification.

If you do not hold a pesticide license, the date you want to hold will be Friday March 10, 2017 at Boyd Auditorium.

More details will be coming so for now get those dates locked in your calendars.

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for 28 years, currently serving Clinton County and the Miami Valley EERA.