Re: Ca:Mg Ratios

Bill Liebhardt (wcliebhardt@ucdavis.edu)
Fri, 20 Feb 1998 12:11:58 -0800

At 01:04 PM 2/19/98 +1300, you wrote:
>At 11:29 AM 18/02/98 -0800, you wrote:
>>It has been interesting to see the dialog on this subject.....
>
>>In the 70's and 80's many commercial labs were using this philosophy or the
>>soil build up and maintenance philosophy or a combination of both which
>>almost always resulted in fertilizer being added even when it was not
>>needed. This was also true with some land grant soil testing labs. Many
>>land grant labs used the sufficiency level approach which basically says you
>>test for a nutrient and if lacking you apply that nutrient.
>
>Bill
>
>This business of SLAN versus BCSR is an area of special interest to me as I
>have been intimately involved in the development of a soil testing system in
>New Zealand and was forced to take a serious look at the pros and cons of
>the different methods. I favor the balance view, as a concept, even though I
>claim to be reasonably au fait with its dubious background. Let me elaborate.
>
>The question really is what happens if you DONT use balance as your basis?
>In my opinion the assessment of individual cations by the sufficiency
>approach can lead to problems of interactions between, for example,
>potassium and other essential cations, such as magnesium and sodium;
>particularly in grazed psture systems where the concern is as much for
>animal health as it is for simply plant yield.
>
>The argument I feel has unfortunately been one of EITHER the "sufficiency
>level" approach OR the "balanced cation ratios" approach, when really a
>combination is a much better solution. We have ample evidence of the
>troubles caused when only the SLAN is used on our grasslands and we
>therefore educate our students about the need to consider balance between
>cations. Hence the BCSR is an attractive concept. It points our fertiliser
>use in the right direction and forces a consideration of the whole complex
>of ions. We also, for the same reasons, embrace the Sumner DRIS method which
>attempts to take balance even further by providing a conceptual framework
>for incorporating soil and plant analysis. DRIS and BCSR have many common
>features. Neither have been thoroughly tested in this country, as yet
>
>Obviously bringing the animal into the equation is a new issue, but in the
>NZ situation we are often dealing with soil tests for pastures destined to
>be eaten by a grazing animal; so you cant leave the animal out. Approaching
>this with the notion of cation balance in the soil and in the plant does
>suggest we are cognisant of the interactions and implications of our
>fertilizer programs to all parts of the system.

MAX, I THINK YOU RAISE SOME VERY INTERESTING AND VALID POINTS. I ALSO THINK
THERE ARE MANY WAYS OF KNOWING RATHER THAN JUST VIA REPLICATED EXPERIMENTS.
THE VALUE OF BALANCE MAYBE IMPORTANT AND YOUR ANIMAL SYSTEMS MAYBE AN
EXAMPLE. WHAT I HAVE SEEN WITH THE BSCR CONCEPT HERE IS THAT THERE IS NO
RESEARCH OR INFORMATION PUBLISHED THAT SUPPORTS USING THIS APPROACH. I
THINK THE IDEA HAS MERIT BUT IT NEEDS SOME INFORMATION TO SHOW THAT IT
REALLY HELPS FORMULATE GOOD NUTRIENT MANAGEMENT. THE RESEARCH WE HAVE TO
DATE DOES NOT SUPPORT THAT.

GOOD FIELD CALIBRATION DATA OR RESEARCH MEANS THAT YOU HAVE DATA TO BACK UP
YOUR NUTRIENT RECOMMENDATIONS. IT IS IN MY OPINION LIKE THE STANDARD CURVE
WE DEVELOP FOR ANY CHEMICAL ANALYSIS. SUPPOSE YOU WENT TO THE DR. FOR AN
ANALYSIS OF YOUR BLOOD GLUCOSE AND THE LAB DID NOT HAVE A STANDARD CURVE FOR
GLUCOSE. YOU WOULD HAVE A NUMBER BUT IT WOULD BE MEANINGLESS-IT IS NUMBER
BUT NOTHING BEHIND IT. IN MY OPINION THAT MAYBE WORSE THAN NOTHING. I HAVE
SEEN FARMERS WITH A SOIL TEST HAVE A PH OF 6.5 WITH BSCR METHOD BEING
ADVISED TO PUT ON CALCIUM SULFATE BECAUSE IT DID NOT HAVE THE SO CALLED
CORRECT RATIO WHEN LOCAL FIELD CALIBRATION DATA SHOWED THAT IT WAS NOT
NECESSARY IF CROP YIELD AND PROFIT IS A CRITERIA. IT IS THE ABUSE OF PROPER
PROCESS THAT IRRITATES ME AND MANY OTHERS IN THIS FIELD. IF YOU CAN COME UP
WITH GOOD NUTRIENT MANAGEMENT WITH BCRS AND DRIS OR WHATEVER CONCEPT AND YOU
HAVE RESEARCH AND DATA TO SHOW IT WORKS AND IS REASONABLE AND IT IS NOT JUST
NUMBER PULLED OUT OF THE AIR THEN THAT IS FINE. YOU HAVE FOLLOWED A PROCESS
THAT IS INTELLECTUALLY AND OPERATIONALLY HONEST AND NOT DECEPTIVE. THAT IN
MY OPINION IS WHAT WE SHOULD STRIVE FOR. IF A FARMER QUESTIONS YOU AS TO WHY
YOU ARE DOING IT ONE WAY OR ANOTHER AND YOU HAVE INFO TO SAY WE DID IT THIS
WAY BECAUSE WE HAVE RESEARCH OR DATA TO BACK UP WHAT WE SAY. THE SLAN
METHOD MAYBE STERILE BUT IT HAS SOMETHING BEHIND IT IN THE US. IT RESULTS IN
ECONOMICALLY, AGRONOMIC ALLY AND ENVIRONMENTALLY SUPERIOR NUTRIENT
MANAGEMENT IN THE US. THERE IS MUCH RESEARCH TO SHOW THAT.

I THINK THAT GOOD SOIL ORGANIC MATTER MANAGEMENT OUT TO BE THE BASIS OF A
HOLISTIC WAY OF MANAGING OUR SOILS. WE CAN DO MORE TO HELP OUR SOILS BY
LOOKING AT THIS ASPECT THAN ALMOST ANYTHING WE DO. THERE IS RESEARCH THAT
SHOWS THAT FARMING SYSTEMS THAT DO A GOOD JOB IN THIS AREA SOLVE SO MANY OF
THE OTHER PROBLEMS ASSOCIATED WITH FARMING.

>
>I find the SLAN methods rather sterile and not so integrative. The idea of
>studying each element in isolation is old science that has not really done
>much for animal welfare in this country. I should add however, that SLAN is
>still the basis on which many scientists and laboratories operate here; even
>in the grassland situation.
>
>I concur however that more research along these lines is needed. In our
>case, it is unlikely to eventuate as funding for soil testing research is a
>very low priority under current economic circumstances.

DEVELOPING FIELD CALIBRATION DATA IN THE US IS NOT WHAT IS SHOULD BE BY ANY
MEANS. IT DID AND DOES NOT RANK HIGH WITH THE PROMOTION PROCESS IN MANY
INSTITUTIONS. IT IS NOT FUNDED WELL HERE ALSO. IT HAS NOT GOT THE PIZZAZZ
THAT SOME AREAS OF ENDEAVOR HAVE. WE ALSO HAVE NOT DONE A GOOD JOB OF
COMMUNICATION WITH THE PUBLIC OR FARMERS ON THIS. I RECENTLY TALKED TO A
FARMER WHO PLOWED DOWN ALFALFA, PUT ON LOTS OF LIQUID MANURE AND APPLIED 250
POUNDS OF N AS FERTILIZER TO GROW SILAGE CORN. HE PROBABLY HAD 600-700
POUNDS OF N PER ACRE. WHEN I ASKED HIM WHY HE USED FERTILIZER N HE SAID HE
WAS ADVISED BY HIS AG CHEM DEALER. THE ALFALFA AND MANURE COUNTED FOR
NOTHING. WE HAVE A LONG WAY TO GO FOR SURE.

BILL LIEBHARDT
>
>You asked for feedback so I have obliged. I will be interested to hear what
>others contribute either for or against.
>
>Cheers
>
>Max
>
>
>Dr Max A. Turner
>Department of Soil Science
>Massey University
>Palmerstonn North
>NEW ZEALAND
>
>
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>

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