Managing Around High Fertilizer Prices – Taking Accurate Soil Samples to Get Accurate Results
It’s hard to talk about fertilizing and soil fertility without starting at soil testing.
For starters, it costs nothing but the time to get out there and do it. But, doing it correctly is critical to getting accurate results. If all you’re going to do is get 3-4 shovels of dirt and put it in a bag, you’d be better off spending that time researching alternative fertilizers (see previous article).
With soil testing, we’re trying to get the most accurate picture of nutrient levels and pH in the field.
The soil fertility in the field isn’t this one big, homogeneous unit where one spot is exactly like another. Due to lots of variables such as topography, soil types, how water moves, what the vegetation is like on top, where livestock tend to congregate, and non-uniform fertilizer applications, it varies. Because of that variability, several samples need to be taken to comprise the sample that goes to the lab. Twenty to twenty-five (20-25) would be a good start. Zig zag all around the field, taking samples down to a depth of 4-6” with a soil probe or shovel (soil probes can be requested at your county Extension office). Put that in a bucket as you go.
Once you’ve completed a field, pick out the larger rocks and plant material, mix it all up, and then take out enough to fill a soil box. The goal is: You want what is going to the lab to be a good average representation of the whole field.
How many acres should I cover with one soil sample?
Also, because of that variability, we typically don’t want any one sample to represent more than 20 acres. For fields that are larger than that, split that sampling however is logical: higher ground/lower ground, rockier areas/less rocky areas, west side/east side. Whatever makes the most sense to you.
The testing doesn’t cost you anything, but when it comes time to spending money on today’s fertilizer prices, it can certainly help to know where to direct that cost.
In the next post or two, we’ll talk about prioritizing applications based on those soil test results. Or, maybe no applications at all...
In the meantime, check out our soil testing resources to get started with gathering your soil sample.