At 5/15/2004 05:57 PM, ShortyB wrote:
>Woody
>
>The grass staggers ratio is an example of numbers from a soil test. Look
>at The Hill lab web site
>http://www.hill-labs.co.nz/Files/PDFs/3193v4.pdf for more
info on
>relationship between minerals for animal health.
>The others are the difference between the minerals. Eg you should have 6
>parts Ca to 1 part Mg.
>Like many good labs Hills http://www.hill-labs.co.nz
>have some useful info for the farmer.
>Just remember guys these have all been developed for Nz farming systems.
Hi Ian,
Actually, the "Grass Staggers" ratio applies to the percentages of K, Ca,
and Mg in the forage, not the soil. The coefficients correct the raw
percentage values for milliequivalents, which is a way of dealing with
differing atomic weights and valences. I downloaded the document and
examined it. We use a similar formula here in the U.S. that gives nearly
identical results.
(Your formula originally listed "Mg/1215" but it should have listed "Mg/12.5")
Also, I would caution that this Grass Staggers ratio is really a dependable
predictor for forages with marginal magnesium values. If I run a "what if"
exercise using a very low Mg value (0.10%) and reasonable K and Ca values,
I can easily obtain a "safe" ratio of less than 2.0, even though from
experience, we can confidently predict that a real forage with those values
would be a very high risk. Conversely, I can obtain a "high risk" ratio of
2.5 with a very high Mg value of 0.28% and a high K of 3.5%. In reality,
this forage would not be a high risk for magnesium tetany because of its
very high Mg level.
But for Mg levels of 0.13% through 0.20% or so, I would indeed look
carefully at a Grass Staggers Ratio and consider it along with other factors.
Best regards.
Woody
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Woody Lane, Ph.D. |
Lane Livestock Services | voice: 541-440-1926
240 Crystal Springs Lane | fax: 541-440-1007
Roseburg, OR 97470 | email: wlane@rosenet.net
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