jbgruver - 11/25/2014 19:57

I've been thinking about potassium quite a bit over the last couple days and am wondering about how Ag Talkers manage potassium.

Answers to any of the following Qs would be of interest to me (and probably many others).

What K sources do you apply and how do you apply? 

0-0-62 broadcast

What is the range of K soil test levels for the soils you farm? please include units (e.g., ppm) and method of extraction if you know (e.g. ammonium acetate)
288#-492# but 90% of the tests are 380#-450#

How much variability have you noticed in K soil test or tissue test results?
The wetter the ground has been before the sample is taken the lower the test result but usually within 50#/acre.

How do you determine what rates of K to apply? e.g., attempt to build up to X ppm or x % saturation
Target 400#

Have you substantially changed K soil test levels on your farm(s) and have you observed clear benefits from these changes?

Yes but it's taken 20 years to go from 200# to 400#. The main benefits has been a much higher bu/N ratio, less yield drag the next year. It used to be hard to have two good crops in a row.If you had good beans one year then the corn next year would suffer and vice versus. 

Do you VRT K products and if so do you have different goals for different soils? Also have your K soil test levels become more uniform?

Yes been on VRT for 6 years. So far the lower test result areas when I began are still responding and yes the soil tests are much more uniform across the field.

Have you ever done any on-farm trials of K products, placements or rates?

Not a very controlled test.

How much confidence do you have in your current approach to K management?

I'm pretty confident what I've done in the last 6 years was beneficial. Areas that were assumed to be poor producers are now within 90% of the assumed good producers. Stalk quality has improved dramatically. I'm tempted to increase populations in corn above 31,000 but this was one of the few years that tip-back wasn't an issue. Really the biggest mystery to me now is P2O5 to K2O test ratios. It seems to me that the areas that got high potash applications are now using more DAP than what crop removal would suggest. I have to remember that the last two years have been truly exceptional.

Some random observations: Soybean stems have gotten much larger near the ground. That might be a reaction to Flexstar and Cobra. There's visible corn residue left 2 years later clear into harvest. This was Disk-ripped not no-till. Corn varieties are the same traits. Might be my imagination but it seems the higher bio-mass in the high K application areas has slowed dry-out in the spring. Not really an issue as they typically aren't the wettest area.      

Thanks for your time.

Joel
WIU Agriculture