In choosing a fertilizer, is the overall ratio of N-P-K important or the individual amounts of N, P, or K the sole qualifying factor?
For example, "Root Stimulators" have a high phosphorous but near-null of N or K.
Another example: Bloom or leaf stimulators have a high amount of nitrogen and little P or K. So is it the ratio of N to P to K? Or amount of a single component N that makes the leaves grow and flowers bloom?
Ratios are tailored to a specific crop. If in doubt or lacking a soil test you can try some 10-10-10 or 5-10-5. But a soil test will help you choose more efficiently.
Remember though that these numbers are ratios. The actual quantities of nutrients could be higher or lower. A soil test is the best place to start. Say, for instance the 5-10-5 could also say 1-2-1, and still be the the same ratio, but the quantity would be higher for each of
5-10-5.What about the other 14 essential elements?
Sincerely,
Are there any recommended sites selling soil tests? I've never tested mine but confess the idea intriques me.
Carl
Carl. There are the simple take home tests for ph levels, N P and K. There are the more sophisticated soil tests run by specialised labs that require you to submit soil and give you a wide range of tests they can run.
rob
Sorry, you're wrong. 5-10-5 has 5 times as much available N, P, and K as
1-2-1. The values are percents of the total weight.They can be simply worked out using the chemical formulas for the ingredients and a table of atomic weights.
Google will pull in a bunch but you are talking about $50 per sample.
I looked into the do-it-yourself aspect and spent less than that for a dozen tests but the results leave me scratching my head.
No matter where I sample in my gardens or across the road in a corn field, I find that nothing could possibly grow anywhere. All the nutrients are below the detectable level and the pH is over 8.
I use chicken, sheep and goat manure every year along with granular fert ever other year so I have little faith in these tests.
I would be interested in knowing what other have learned using these.
js
I second Andrew on this. The NPK numbers are not ratios, but rather percentages. Numbers like 10-10-10 mean that the fertilizer has 10% of each NPK component. 5-10-5 does not contain the same amount of NPK as
1-2-1. If you're talking ratio, yes the ratios are the same, but the total amount of NPK is much higher in the 5-10-5 fert. Also, FWIW, higher NPK numbers don't mean the fert is of higher quality. Typically synthetic ferts have higher NPK numbers than organic ferts, but it can be argued that organic ferts are better in quality because they have other nutrients that plants require for good health.Layne
Typically, the state agricultural university or the extension service offers tests, though I know that's not true in all states. At least as of a few years ago, Iowa State's soil lab would accept out of state samples for testing, but you'd have a very long wait in the rush season (Feb-May), as in state farm samples have priority. Note sampling guidelines.
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