Townsend, Montana | Mbmaring - 10/21/2024 22:16
Seems like if you fertilize for a poor crop your sure to get it. We have pulled some pretty large crops off the fields the last few years and our p levels have really dropped. Have some fields showing only 3 on the Olson test
I agree. Our soil typically tests 3 or 4 on the Olson test as well. Doesn't matter how much MAP, DAP, MESZ, elemental sulfur, AMS, or Ortho phosphate we apply or when we apply it, we can't move the soil test at all and never see a yield response. Drove me nuts for the first few years I farmed.
Came to the conclusion that our irrigation water is tying up the phosphate even faster than the soil can. Banding on our dryland works great. Doesn't do a darn thing on the irrigated.
Even though we can't get our P to where it should be, we get yields equal to or better than most of the county so I can't complain. We just seem to have a 100 - 110 bu yield ceiling for wheat. Doesn't matter spring or winter wheat (most WW in the county will easily do 120+, spring wheat struggles to hit 100 most places) or what our fertilizer program is. We grow 100 BU wheat. Protein depends mostly on N. Increasing water infiltration rates seems to increase standability and protein for the n applied and maybe a slight bump in yield. I suspect it has to do with more aerobic soil activity and thus better K uptake.
The head scratcher for me now is orchard grass. We will kill out an alfalfa field and plant orchard grass into it. When we terminate the alfalfa, the P levels are in the 3 to 4 range, just like every soil test that has ever came off of this farm. After a few years in orchard grass with nothing but UAN, urea, and elemental sulfur, soil test P levels will be in the 12 to 15 range. One year back in alfalfa or wheat and it's back down to 3 to 4.
Total P is over 10,000 PPM. The phosphate is there, plants just struggle to utilize it. But plants in my soil seem to be able to mine it better than the Olson test would suggest.
Edited by 1972RedNeck 10/21/2024 23:19
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