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Aberdeen MS | While there always has been a question to many about the validity of the recs, my answer is NO.
Keep in mind that when sampling and recs became common place, it was the dealers that requested a "guideline" to put in front of the customer in black and white to comfort the farmer that the dealer wasn't "just putting numbers out". The Land Grant colleges took on the task and things progressed from there.
There is solid chemistry evidence as to the removal of nutrients from the grain removed.
What is difficult to get across to growers in todays world, is that same Land Grant process that has been a comfort zone for the last .... what.... 60 - 70+ yrs??????
What you are seeing is an over application in regards to the soils ability to "tie up" nutrients. Your assessment on broadcast rates are correct. Tillage incorporation doesn't really come into play.
The soil is only capable of holding XXX amount of nutrients due to the chemistry makeup of that particular soil. CEC, pH and a number of other factors determine what amount that is. In the banding situation, you are over loading the soils ability to hold/tie up, the remainder is in more of a "free form" that the plant goes after first. Take the easy stuff first....go after the hard to get later.
Thus.... more of the tie up is still there in your situation because the crop was able utilize the "free form" rather than take from the natural release that occurs in a X time frame from previous broadcast applications.
The U of MN has done some research, but I don't have the actual reports handy to me, or if any/many of them are even finished yet. I've just heard the results being spoken of at various meetings.
Here is something for you to think about and "chew on". A 150 bu corn crop will remove somewhere in the neighborhood of 35 units of P, I think that's kind of a common figure that many..certainly not all tho... will agree on. When applying that rate of removal in a dry form in a broadcast situation ( certainly not a "no no" to common practices), somewhere in the neighborhood of 20% of applied will be available to the crop that growing season. 20% of 35 is 7. The remainder comes from the natural release from early applications. You are adding and taking from the soil profile at the same time to achieve the next years yield.
When banding...over "saturating" the band to minimize natural tie up, you are leaving the release to remain and taking from the "free form" I mentioned earlier.
Hope this helps somewhat. How much can you reduce the application??? I'll leave that to the CCA's with a better grip on soil sciences to address that. It's been 30+ yrs since my soils classes at NDSU.
Bruce | |
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P&K + StripTill
