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Aberdeen MS | The key to determining that question is to first sample. And sample extensively.
Granted that sampling isn't an exact science, but at this point in time.... it's the best we have to determine what MIGHT be for the upcoming year. Tissue sampling will verify IF the sampling is/was correct.
Like Jim mentioned, the 50% cut advise is from the "broadcast/build" recs that were commonly followed in years past, that is a finding of the U of Mn, not just some number pulled out of the air by the proponents of the idea.
A quick google search on P and K removal per bushel of corn and this report from the U of Mn was the third return.
http://www.extension.umn.edu/cropenews/2007/07MNCN37.html
"To calculate crop removal, anticipated or expected corn yields chosen were 150 bu. per acre at the Southwest Regional Center and 170 bu. per acre at the Southern Center. This report will deal with corn production only. Phosphorus removed in a bushel of corn was the same at both locations (0.15 lb. P per bushel = 0.35 lb. P2O5 per bushel). .........."
That translated into 22.5# of actual P removed in that test by 150bu/ac corn.
Another finding in the same article reports this:
"By using the crop removal concept as a guide, there is an implied assumption that rate of phosphate fertilizer applied should change with the relative level of corn yield. The yield data from the trial at the Southwest Research and Outreach Center do not support this assumption. The rate of phosphate fertilizer needed to achieve optimum yield did not change with yield level.
Use of the crop removal concept assumes that all of the nutrients applied in a fertilizer program are used by the growing crop. This, however, is not what happens when nutrients are applied to soil. Depending on the nutrient and the chemistry of the soil, utilization or uptake from various sources has ranged from 20% to 65% of that applied. Research has shown that instances are rare when nearly 100% of an applied nutrient is used by a growing crop."
The soil properties vary vastly around the country ... and even within the same field. By knowing that not all the applied nutrients are utilized in the application year, the concept of banding is to "super concentrate" the nutrient applied at the source to reduce the "tie up" capability of the soil and it's effect on the nutrient. It's like a sponge, take a small one in a glass of water... you have a lot of water left over when the sponge is full. Put a large sponge in the glass.... it will soak up all or almost all of the water leaving the glass empty. The soil in your fields is the sponge and it can only hold so much.
Once the soil surrounding the band is "saturated", the remaining nutrient is then available for the plant to use. Over time and by moving the "band" year to year, you MAY effectively create a soil profile that has increased in reserves. That has been researched again by the U of Mn, not just a theory dreamed up by the proponents of nutrient banding. The concept of banding has been around and verified for years. and proven that it works. If it didn't..... no till wouldn't be able to produce yields comparable to broad spectrum tillage. It's not a new concept. The concept is just getting more attention because strip till is a new venue for crop production.
One has to remember the reason soil sampling was initiated in the first place. Fertilizer dealers had no idea of what to recommend and show in black in white to a grower what to apply in the many many years past when commercial fertilizer was first being used. Fertilizer suppliers (not your local dealer) came up with "data" to show what was needed and its been an accepted practice over the last 60+ yrs or so. That all worked well and good when fertilizer was cheap, if X amount was good...that means that X++ amount has to be that much better, that's not the case anymore.
IMO, many dollars has been wasted over the years by constant over application of nutrients just because it was cheap and growers saw it as an insurance policy. Reality says a particular piece of ground will only produce Y amount of grain regardless of what the grower puts on it (unless of course it's a pampered piece like the record holders do in competition). I call that the "balance" of economic return and agronomic return. THAT number is different for every grower, every field, every growing practice that is implemented for each and every field across the US.
The challenge many are stepping up to now is attempting to find that balance and accept what their ground can produce. | |
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How much fert can a guy cut out with strip till?
