Since 1982 I have been an independent crop consultant. I have spent my time analyzing what was in my clients’ soil and what travels up into the plants. I do soil testing, plant analysis, test plots and whatever else needs to be done to make their nutrient use as efficient as possible.
After taking the soil tests, I review the results with the farmer to make sure he knows and understands what the numbers mean. It is important that he understands where his levels are at, where they should be and how we are going to get to the desired levels.
By doing plant analysis on each farm, it gives us more information to work with. Soil tests are a beginning but the plants tie it all together. The most reliable readings in the soil test are phosphate, potash, calcium and magnesium, which are the major nutrients.
If phosphate levels are medium to high in the soil tests, it will be at a sufficient level in the plant. If you raise the levels in the soil to a very high level, it will not raise the levels in the plant. Weather will not affect the plants’ levels either.
Potash levels in the soil will be determined by the cation exchange capacity. This reading represents the amount of clay in the area soil tested and determines how much “K” it can maintain in the exchangeable form. The plants’ potash levels will be more variable. Soil test levels and dry weather control plant levels; more management is needed with this nutrient.
I do not run sulfur or micronutrient analysis with my soil tests. Sulfur tests produce the most inaccurate results. I have always run plant analysis; therefore, I can look at tests results from 33 years ago and see there is no difference in the sulfur levels. Burning less high-sulfur coal has had no effect on plant levels for my clientele. The levels in the plant continue to be very consistent and adequate.
Micronutrients, such as zinc and manganese, also are consistent in plants. The numbers are in the sufficient range 95% of the time. If I were to see a pattern of low readings, I would then do some test plots, adding these nutrients and following up with yield checks. Most of the time, I find that there is not a yield response from adding the nutrients.
With numerous agronomists voicing varying opinions on sulfur and micronutrient needs, farmers find it difficult to know what to do. With these nutrients rely on plant tissue tests to make a decision, not just on the person recommending their use.