Source: Central Valley Ag

Last week, I tried to help you understand how cutting back your crop removal rates would affect two things, your budget, and your yield. Throughout that entire discussion, I decided to simplify things; work under that assumption that we have consistent fertility needs across our entire field. Of course, that assumption is an oversimplification. We know that even on flat fields, there can be, and often is wide swings in soil fertility level. Whether from erosion, differences in cropping history, old farmstead locations, or a plethora of other reasons. So as we continue to be mindful about how we allocate our resources, we need to think about how and why we apply the rates we do. And the answer to those questions is intensive soil sampling.

Far too often, we tend to think about soil sampling as a line item expense. Something to do when times are good, but can be delayed when budgets are tighter. That couldn’t be further from the truth, especially for those that are in their second, third, or even fourth cycle of soil sampling. I could talk about this all day in a superficial sense, or we could just get down to the numbers.

At CVA, we have a few choices in soil sampling types depending on where you are. Those choices include Grid or Zone Samples. On the Grid side, you can choose to pay in a single year, or over three years. With the three-year payment option, your cost per acre is about 1 bushel of corn at today’s price for a re-grid or slightly little more for a new grid. On the Zone side, things are somewhat different because we sample every year in our four-year cycle, but for our Standard Lidar Zone we are about 1.3 bushels per acre, and for our advanced zones that use EC Data and RTK elevation, it is about 1.9 bushels per acre.

Now, of course, intensive soil sampling doesn’t give us its full potential unless we use Variable Rate application to apply nutrients, so let’s assume that we are going to Variable Rate Multiple Products and have a VR Prescription charge add as well. So we could have a re-grid package that costs us 1.9 bu/A per year to apply, up to an Advanced Zone package that was 2.75 bu/A per year. The real question becomes, how likely is it that intensive soil sampling and VR Fertilizer application will save me more than my 2.75 bushels max spend?

To find that answer, let’s look at the International Plant Nutrition Institute. I have talked about them before as a resource to look at trends and averages when it comes to soil test levels. So I went ahead and queried the 2015 results for Nebraska, Iowa, and Kansas (fear not as there was seldom more than a 2% difference in the average vs. any ones states values) for Phosphorus, Potassium, and pH.

When I look at Phosphorus, 17.4% of all the samples came in at or above 50 ppm. That means that levels would support less than full crop removal, and certainly in some instances no crop removal. 17.4 % of our acres not needing Phosphate (on average) would equate to a 2 bushel per acre savings. Potassium has 24.3% of test over 320 ppm. There are many different philosophies on how to decide when and where to apply Potash, but I am confident that those acres would qualify for less than to no crop removal. That 24.3% of acres on average not needing K would save us the equivalent of another 1.4 bu/A. When I look at pH, 43.4% of acres need no Lime application at this time. That would equate to an average savings of 3.5 bu/Acre.

So in just those three nutrient categories, you can see how the averages say the savings should be around 6.9 bu per acre, while sampling costs are between 1.9-2.8 bushels per acre. That of course pencils out to the average savings coming in over 4bu/A. This also is only looking at placing crop removal needs for maximum efficiency and minimum expense. Intensive soil sampling will also identify areas with deficiencies that are costing us yield due to low nutrient levels or low pH. Addressing those deviancies will undoubtedly also improve bottom-line performance.

The total samples for Iowa, Nebraska, and Kansas the IPNI had reported to them for soil fertility values was almost 1.8 million in 2015. That, of course, means that these numbers may not hold true for every parcel of ground that you farm, but the overall trends should match up with your neighborhood. Throwing a full rate of crop removal out on every acre of your farm may still be the right thing to do in 2019, or it could be overkill. The only way we will know for sure is with a good soil sampling program. So please, keep this in mind as you work towards getting your crops out this fall, the averages say that not only is intensive sampling and VRT a good idea in these economic times, but averages say that your field is going to pay you to do it.