Soil sampling season is definitely here, and many producers are now using grid or management zone sampling rather than low-density soil sampling.
Grid sampling has been around for many years, but we still receive questions whether it’s a good investment.
The more variable your fields, the more valuable grid sampling is to find and correct nutrient-deficient areas. The only way to determine if fields contain highly variable nutrient levels is to grid sample them at least once. Just because a field is flat and seems uniform, doesn’t mean that field’s soil tests will come out uniform.
Last year, we sampled our whole farm on 2-acre grids. We learned where the variability was located and we now have a better understanding of how to fertilize our fields.
In Table 1, you can see how results of potassium soil tests in a field sampled with a more standard manner of seven samples for 54 acres compared to 27 samples on 2-acre grids.
Standard sampling showed that about 86% of the samples were in the optimum to high range and 14% were in the very high range, indicating the field contains very good fertility.
However, grid sampling showed that 7.5% of the samples were in the low range, 70% were in the optimum to high range and 22% were in the very high to extremely high range.
The grid sampling revealed the acres (7.5%) that needed additional fertility. These areas of the field will likely continue to fall in potassium tests…