NORTH PLATTE, Neb. — So you pulled some soil cores and now you have the results in your hand, now what? On your soil test results you will want to check out pH, potassium, and phosphorous levels across all soil textures. If you have a lighter textured soil, check for sulfur levels as well. Today we will focus on pH and potassium recommendations.
For pH, you will want to see a soil test result of 6.2 to 7.0. This range allows alfalfa to have high nodulation and is a range that many of the essential nutrients are readily available. With established alfalfa, adjusting pH is challenging and surface application of lime can affect the upper 2 to 3 inches of the soil profile. However, a pH issue in an established stand can cause decreased nodulation and may be a sign to renovate. Bottom line in alfalfa: it is best to be correct the pH issue at least 4 to 6 months before establishment. Correcting pH in established fields is very difficult and may be a signal to renovate.
Potassium is measured in parts per million or ppm on your soil test sheet. If your test ranges from 126 to greater than or equal to 150, then you do not need to apply potash. If your test ranges from 0-40 (apply 120 lbs. potash/acre), 41-74 (apply 80 lbs. potash/acre), and 75-125 (apply 40 lbs. potash/acre). Potash can be applied in the fall following the last cutting and is recommended yearly for irrigated and in 2 year cycles for dryland.
Remember if you are still wanting to pull soil cores, you will want to sample at 8 inches or historic depth. Collect samples by grid, soil type, or representative area (40 acres or less). Then pull 10 to 15 random soil cores and combine in a plastic bucket. Take about a pint of soil and submit to an accredited lab. If you have questions please contact your local extension educator or agronomist.
— Megan Taylor, Nebraska Extension
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