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How do you manage potassium?
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Posted 11/26/2014 05:04 (#4201958 - in reply to #4201345)
Subject: RE: How do you manage potassium?


NE Iowa
What K sources do you apply and how do you apply? 0-0-60. Have high super high Mg soils so would love to use potassium sulfate but no one handles it in my area and the prices I've seen are on it are really high. I no-till everything so all K is just broadcast and not incorporated. Bean and corn fields are spread in the fall. Alfalfa is topdressed after the first and third cuttings every year.

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) Around 150 ppm average on tests from A&L labs but no idea what extraction. Maybe down to 100 coming out of alfalfa or up to 250 on fields that used to be hog lots 60 years ago.

How much variability have you noticed in K soil test or tissue test results? K levels seem pretty consistent from soil test to soil test. What I mean is a field will likely test very similar if you do it every year or every other year. Potassium extraction must be easy and therefore more repeatable then other nutrient tests.

How do you determine what rates of K to apply? e.g., attempt to build up to X ppm or x % saturation - I would love to get up to 4% saturation on every field. Just hard to spend the money $$$. My fields that are at 4% K are my best yielders year in and year out.

Have you substantially changed K soil test levels on your farm(s) and have you observed clear benefits from these changes? Have bumped from "medium" level to "optimum" category in the last 10 years on soil tests.

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? No VRT but have small fields and sample often so have developed more uniformity in K levels by adjusting field by field in the last 10 years.

Have you ever done any on-farm trials of K products, placements or rates? My fields are all steep and contoured so not consistent enough to do much trial work.

How much confidence do you have in your current approach to K management? I am confident that there is a pretty strong relationship between K level and yield. It really shows in alfalfa and also is more prominent in a dry year. My biggest hurdle is spending the $$$ it takes to get all fields up to 4% K that I want.
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