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| Ron,
Tissue tests are snapshots in time. Need to see a series before you get an idea as to what's happening.
Soil tests have decent predictive value for N, P, and a few other nutrients. Soil tests are rather poor on copper and nearly worthless on molybdenum. Plant tissue tests are ideal for sorting those out. Problems with soil tests include complications with soil biology and other things (chemical reactions, uptake antagonisms, etc) rendering the nutrients unavailable. The tissue analysis removes one entire level of assumptions -- the soil test assumes that nutrient X will be taken up by the plant, but with the tissue analysis it is already in the plant and we can see how much is there.
Genetics certainly influence uptake and plant needs for various nutrients. But most of today's corn hybrids and soybean varieties are fairly closely related to one another (especially corn) and will behave similarly. Environment (climate, diseases, etc) will influence uptake of nutrients more than genetics in this case. The point is to not over-emphasize any single result, but try to see the picture of what your limiting factors are. Along those lines, the interpretation is key -- the interpretive values used out by the laboratories may or may not be accurate. Comparison samples (good vs. not so good plants) are often the best to decipher what is happening. | |
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Tissue tests?
