Fall Soil Testing

By Nick Dunn

Producers have been testing their soil for many years. Many of them wonder if it is worth the investment to make annually, or question if they should even do it at all?

The answer is not that simple. For starters, the soil sample data collected is only as accurate as how the field was sampled. There is no value in analyzing data if the sampling method conducted was not proficient. Similarly, there is no value in sampling if you are not going to incorporate the findings into your fertility plan.

The main reason we sample soil is to make informed decisions about changing and adjusting our fertility plans that directly reflect soil conservation and control input costs. Those who sample do so on a regular basis (whether that is annually, bi-annually, or even every 5-10 years) to collect data and build records to monitor the activity of our soil health in relation to our farming practices. With market prices trending upward, I would expect to see more producers exploring their soil’s health, bringing more efficacy to their operation, and protecting their bottom line, especially when the investment is made to incorporate Variable Rate Technology (VRT) with equipment. Along with other historic data, soil sampling is the backbone and will inform you on the 4R Nutrient Management plan (using the right source, right rate, right time and right place). The more data the better; some data is better than none – the choice is yours.

When is the best time to soil sample? It is really six of one, half dozen of the other. Personal preferences may change from year to year. My personal preference is to sample soil in the fall if time permits and here is why. Your soil health changes from year to year but will have very minimal changes from fall to spring due to freezing up. In fact, it may be more reflective as to what can be expected in the spring in terms of soil moisture. For most growers, things slow down once the crops are in the bin. Rather than waiting until the busy season for everyone, including the retailers and laboratories, get ahead of the game. Spring is typically wet and can make it hard to obtain samples in a timely manner. Fall sampling will also give you lots of time for planning over the winter. Often when buying inputs, if you can pre-buy in the fall and winter, you’re eligible for greater discounts and promotions as compared to in the spring or maybe you want to apply fertilizer in the fall after demand and pricing drop. Learning from last year’s experiences with the supply chain, showing early commitment might be the deciding factor of who gets what and how much – hard to do that without a finalized fertility plan.

Whether you sample in the spring or fall, it is important to keep the soil sampling method consistent. Any inconsistencies can affect the data analyzation and deplete the purpose of the initial investment. It’s also important to save your data for reference in the years to come. You paid for it, why throw it out? If you have problematic areas in the future, this will be something for yourself or your agronomist to investigate.

There are many ways to go about soil sampling; you could either hire it out or do it yourself. You could look into retailers and vendors who offer these services and would often provide something they can sell you, such as software, inputs, or agronomy advice. The benefit of doing it yourself is no one knows your land better than you do. This will help in obtaining a proficient sample. There is a great return tied to soil sampling that will also increase the efficacy and revenue in many aspects of your farming operation.

Nick Dunn is Flagstaff County’s Agricultural Fieldman. He can be reached via email at: or by phone at: 780-384-4138.