Will all that dry P and K that we apply this fall be available next spring? That is the question that I struggle with after getting my soil sample results that we pulled this fall.
Since harvest ended so early, I wanted to get caught up with our sampling that needed to be done last year, but was not able to since we had a late, wet harvest. I resisted initially to pull samples this fall because of the dry soil. It seems that when we sample in dry soils, our results are somewhat skewed, especially with low phosphorus levels. But this year, we were up against 3 to 4 years in not pulling samples on some farms and it was a perfect fall to lime. So after a half-inch rain, we pulled the trigger and sampled several hundred acres.
The results are in and just as I expected, the P results were a lot lower than I expected, whereas also some K levels were on the minimum range. Our samples are sent to Midwest Labs to get not only what levels are in our soil, but also what is available to next year’s crop.
My dilemma is this. Should I apply the recommended P and K rates this fall based on my tests and would it be readily available to my corn and soybean crop next year?
I will definitely apply lime based on what is needed, but applying P and K at the full rates is something I’m hesitant to do because I feel my return on investment with $470 per ton of K and $650 per ton of P will not be fully utilized.
My plan of action is this. On my soybean crop next year, I will broadcast what is needed because basically it would be the only opportunity to fertilize what is needed. But on my corn crop, I plan on applying a minimum amount of dry P and K because of the opportunity to put on what is needed with my corn planter and with my applicator.
With my corn planter, I plan on adding 4 gallon of 10-34-0 with my 28% and Thiosal. The agronomist experts have told me that the corn plant uses most of its phosphate up front before tassel and that P moves very slowly, and they say a lot of K is used on the back end of the growing season. So, instead of having my total amount of P and K laying on top in the dry form, why not have it also be readily available in the liquid form in my side band?
Having a minimum amount of N-P-K with my pop-up fertilizer and adding some with my side band, it seems to me that it would be readily available when needed. Then at sidedress time, I plan on adding 10 gallon of 4-10-10 with my 28 and thio to give me some added K when needed after tassel.
Even though I will have to handle more liquid with the planter and at sidedress time, I really feel that my investment in my fertilizer would be used more efficiently. I also have to manage each field differently with mixing needed amounts on the go, so this will take an extra effort and patience on my part. But having a full recommended rate broadcast this fall seems like a lot of money that would be a hit or miss for the corn crop.
With the mineralization we have in our no-till soils, I just smile when I see these recommended rates from the universities of what is needed to produce a corn and soybean crop. It would be hard for me to survive financially to spend the kind of money that is applied with the amount of N-P-K that conventional folks use. Another good reason to appreciate that no-till is king.