From Steve Larocque, Beyond Agronomy:
The addition of potassium fertilizer has long been debated in our area due to the high background levels of potassium. Research from Alberta Agriculture has shown that a response to potassium fertilizer is unlikely when soil test levels reach 125 ppm or 250 lbs/ac. However, based on the results of variable rate potassium in canola, perhaps we need to revisit this assumption.
Garth Donald from Decisive Farming shared the zone soil test info showing a response to potassium fertilizer on a high potassium soil.
The potassium was applied at a rate of 45 lbs/ac actual to Zone 2 where potassium levels show 286 ppm or 572 lbs/ac in the top six inches. The Base Saturation levels which some folks call BS, is below 4% and under the ideal level of 4-6%. Interestingly enough, this Liberty Link canola, L-150 responded to potassium fertilizer on a soil that contained twice the level where research suggests we should see a response.
Potassium’s role in canola production is to help transport nitrogen up through the xylem and throughout the plant. It plays a key role in over 60 enzyme interactions which drive photosynthesis, improve nutrient uptake, increase plant vigour and even maturity. For these reasons I suspect we are seeing a response from the potassium as it drives root growth, vigour and crop maturity. For more on potassium’s role in plants click here http://agriculturesolutions.ca/Agriculture_Solutions_AEA_PHT_P/Functions%20of%20Potassium.pdf
It’s not often we get to see a side by side like this one and even if it doesn’t translate to yield, which it probably will, gaining a week’s maturity inside our 100-110 day growing season is golden. Those of you on high potassium soils may want to initiate your own research and test the theories that have always been held as gospel. SL