What factors did you take into consideration when it came time to deciding your soil fertility program? We recently came across an article published by MSU Extension that claims: “Practically speaking, the time required obtaining soil samples and the sampling budget dictate the number of soil samples that should be taken.”[i] Of course, this would make the most sense when it comes to collecting soil samples, but if time and money restraints were not an issue for you, the research confirms that grid sampling, with higher amounts of subsamples, provides you with the most accurate results to represent what’s in your fields. Luckily, the use of the Falcon Automated Soil Sampler allows you to easily incorporate grid soil sampling into your operation while also supporting you to collect higher amounts of subsamples, in just a fraction of the time.
So what’s the big deal about quality when it comes to soil sampling? Because your lab results are the basis for the recommendations you are creating, input costs for your operation and your soil fertility are directly affected by the accuracy of the sample result. It is absolutely imperative to make sure that the samples you take accurately represent your fields: “a good soil sample that adequately represents your field or area gives you good results. A poor sample will only lead to an analysis of limited value and be a waste of your time and money.”[ii] If time and money already have significant impacts on the sampling method you chose for your fertility plan, collecting samples that don’t accurately represent what’s in your ground further restricts the productivity of your operation. Keep in mind, the whole reason for soil sampling is for you to gain an understanding into the nutrients in your field before you use recommendations when it comes time to spreading: “for those wishing to obtain more knowledge about nutrient variability within a field and to possibly increase productivity, a more intensive sampling program should be used.”[iii]
It’s easy to understand that a more intensive sampling method will give you a better idea of your soil’s nutrients, so let’s look at how beneficial grid sampling actually is. The MSU Extension explains that grid sampling, “avoids sampling bias that could result from the collection of an unrepresentative composite sample due to a high portion of subsamples collected from the same region.”[iv] Think about it this way, check out this bowl of rainbow sherbet to the left. If you were to take one bite of only the green portion, you would miss out on all of the other flavors and you wouldn’t have a fair representation of the whole (not to mention that the green part only makes up a very small portion of the entire bowl of sherbet in this case). This example may be an extremely simplified way to think about soil sampling since you would never have to worry about fertilizer and spreading costs after eating a frozen dessert, yet it gives you an idea of how easily an unrepresentative composite sample could sway your fertility plan.
Are all grid sizes created equal? Not exactly. SDU explains: “A number of studies have determined that the largest grid size that will adequately measure nutrient variability for a field should be no more than 2.5 acres in size. In fact, many studies have shown the size should be less than one acre.”[v] So we know that grid sampling will remove bias representations from our lab results, and that grid sizes 2.5 acres and under best measure nutrient variability, but what about the number of subsamples collected within each of your grids? Based on research conducted by NDSU soil scientists, “A minimum of 20 subsamples from a field should provide a soil sample with sufficient accuracy for soil testing purposes. If more accuracy is desired, more than 20 subsamples should be taken from a field.”[vi]
Ask your soil sampler how many cores they take with a hand probe and they will likely respond with something around 5 to 8 cores. While 5-8 cores may seem like a lot to give you an accurate composite sample to send off to the lab, Kansas State recently published an article based on past research from NDSU and states that 8 samples or less to represent a larger area will give you, at least, a level of accuracy as poor or plus minus 25%. Can you afford to let your input costs swing plus or minus 25% off of your budget because of a poor soil test? We surely don’t think you should have to. Per the Kansas State article, “Taking 20-30 cores will provide more accurate results (Figure 1). A greater number of cores should be taken on larger fields than smaller fields but not necessarily in direct proportion to the greater average. A single core is not an acceptable sample.”[vii] We included the graph that Kansas State used in their article, along with the methods that would provide you with the respective number of cores.
As you can see, 181 cores will provide you with the most accurate representation of each sample. We also added images of typical soil sampling technologies as well as an estimated number of cores each technology would take in the same amount of time it would take the Falcon Automated Soil Sampler. The Falcon easily takes the highest number of cores to create your soil sample. When you consider the amount of time you may have to sample this intensively, keep in mind that the Falcon is run at an average speed of 8mph, and will collect cores every 15ft, or ever 7.5ft if you add an additional probe to the device. If we go back to the understanding that both time and money allowances are considered for soil programs, time is not an issue when you use the Falcon to collect high-density subsamples for your grid sampling.
Do accurate soil samples have that much of an effect on your operation? Of course, it does, or else why would we waste time sampling at all? Ohio’s Country Journal published an article a few years ago stressing the importance of intensive soil sampling that claims:, “There is the opportunity to gross $1,000 or more per cropland acre, and a farmer wants to capture as much of that as possible by applying costly fertilizer and lime at peak efficiency.”[viii] With many uncomfortable factors in your environment today, why would you not try to control what you can, when you can? The Falcon becomes an easy choice when you can ensure an efficient, and high-quality, soil sample to dial in your soil fertility program.