Southeastern, PA. 30 miles west of Phila | This is related to the thread below reminds me of a questions that I have yet to get an answer that I can understand.
I agree that anytime what you put on drops below the removal rate you are mining your soil. So how were the removal rates that are commonly use on grain crops determined however many years ago?
The reason for this question is this spring I was taking some tissue samples of my wheat. (I was at a meeting during the winter where they really cracked up tissue sampling as a good tool to learn what is really going on out in your fields) So when I get the samples back the N & K were around 4-5% which according to the lab was ideal and the P was around 0.3%. If I remember correctly the P was just a little low but not much. Now the real kicker is the removal rate for P is only 10 or 20 lbs less than the K.
So according to my tissue sample I am either over applying P or K because why would a crop with almost equal removal rates of two nutrients have such a huge difference on an "acceptable" range on the sample?
And to further confuse things the N & K on a wheat tissue sample should be almost identical, yet I apply 50% more units of N than I apply of K.
Here is my theory for each of these nutrients:
Nitrogen: We lost a fair amount to mineralization and leaching that we are applying the correct rate, the tissue sample is just showing a little actually gets into the plant compared to K
Potash: This nutrient moves through the soil so slow that in most cases we remove everything we apply so the crop removal rates are correct.
Phosphorous: Because of the charge of this nutrient; so much of it gets tied up in the soil, never to become avaliable again that our crop removal rates are much higher than they actualy are to compensate for our inefficient methods of applying P.
This thread is a question not a statement of how I believe. My theory is just that; so please tell me what I am missing.
Merlin |
What defines removal rates?
