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Little River, TX | Eddie,
Not specifically for No Till, except to "strip till" in as much of your fertilizers as possible.
Most labs have provide a stage of growth to sample. Many use ether a whole top, or a selected portion of the plant to be sampled. On their end the chemistry is the same regardless, but the interpretation will be different.
The good thing about plant analysis is they all use the same chemistry, and there is no interpretation for soil type. The result is the numbers from New York or Iowa will compare with the numbers from Texas or Georgia.
Then you simply look at the reported values, and compare them to the critical and sufficient values. Below the critical ranges some fertilizers should see a positive crop response. In the sufficient range there is little expectation for a positive crop response.
The major complaint for plant analysis is it only tells us what is the one limiting element is. It does hint at other problems though. There is a method of looking at ratios, and there are some ideal ratios for optimal production. Say the optimal range for N/S is in the 15/1 range & yours is 19/1 are you high in N or low in S? Looking at N/P, P/S, N/S you will help. If it is thought to be S you
can look at N/K & N/Ca, and if they are good then you need sulfur.
The simple method is if the it is say 3.00% N & 0.12% S you need sulfur and it is your primary limiting element. You address that and next sampling you will learn of different primary limiting factor. It is earlier detection of the lessor limiting elements.
What I use plant analysis for is to validate my fertility program for this year and plan for my fertility program for the next crop.
The problem I have with all soil test results is the recommendations. A soil test is only a little better than a wild guess unless that Lab has validated its findings with cropping results in that soil. For a generation or more we were told our soil was VH in P & K. Turns out we needed some P and a whole lot of K. They also told us we had excessive calcium with a resulting high pH. That is true.
One thing, the cations work together in some ways. When my plant analyst was low in K it was excessively high in Ca. When I put a ton of potash on the soil, not only did the K % improve but the Ca % came down to a normal level. So far the magnesium levels have remained sufficient.
A rule of thumb.
Just as when we put out high amounts of Phosphate we also need to put out some zinc, when I put out copper I also need to put out some Moly. If a whole lot of nitrogen is used you may need sulfur if you want a high protein level.
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Tissue tests?
