Are Late Soil Sample Valuable?
Delayed soil sampling efforts because of extreme wet conditions and late harvest create a question of whether to use last year’s samples or pull a new one now. For me, the answer is yes. I would do both. I believe the questions of pH and phosphorus can be determined using last older soil samples. The phosphorus levels tend to remain more consistent so the levels from a year or two ago should remain somewhat similar. Also, P deficiency in cotton is rare and only needed in lower amounts compared to other crops. Our soils typically run good P levels. The pH is somewhat predictable so we could use a year-old sample and consider what crop and fertilizer was used for 2020 to calculate how much acidity was produced to estimate the need for lime this year. A problem with a winter sample that is pulled in cool wet conditions is that it seems to give a false higher pH than what you would find in warmer soil when the crop is growing. It is a trend that I have noticed over the years. Regardless, with the tremendous amount of rain we have experienced, it would be good to have a late sample to look at what the levels of nutrients that are more leachable are now. Potassium (K) is the best example of a soil nutrient that can leach and is likely at lower levels on soils with a low CEC. Let me know if I can help you with soil sample interpretation or developing a fertility plan.
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