Vaughn, what a fantastic amount of work you have put in to tell this story
so well about the unreliability of soil testing. I am sure that few will
disagree with you and even if you were to ask the laboratories, the ones I
know would often agree with your sentiment.
During the last 15 years I have increasingly investigated the relevance of
biological status of soils to their performance and health. Only when soil
fertility is explained in 3 dimensions - nutrients, physical structure
(cations) and biology - can we realistically start to gain the full
potential of reliable production, resilience and health from our most
valuable growing resource. It has become apparent that the soil testing
methods used to this day are only relevant when taking into consideration
the transfer and uptake of nutrients in a soluble form by plants. As anyone
who understands soil function will tell you, the application and benefit of
(mainly) water soluble inputs on soils are short lived, short sighted and of
little long term value - except for the fertiliser companies!
It is certainly time to challenge the current paradigm and bring biological
processes into ALL the management considerations when dealing with soils,
plants and animals. It is in this thinking that the various phenomena can
begin to be explained. Increasingly research is showing that microbiological
life (in soils, the gut or any other digestive process) acts as a buffer and
in itself will have a significant effect on, among many other factors, even
a basic measure such as pH. Biology also plays a key role in maintaining
soil structure and is the most efficient medium to hold nutrients in soils.
When one learns that over a hectare(approx 2.5 acres) of moderately healthy
soil in a pasture situation holds at least the equivalent of the body weight
of a cow in soil microbiology (Bacteria, fungi, protozoa, nematodes) and
another cow's weight in earthworms per hectare all willing to work day and
night as long as there is moisture, food and energy from the sun to live,
then clever farming can begin.
It is already happening that the results of research are moving into the
paddock and shown to work in a practical way on farm. Potentially all the
soil tests currently in use except for total values of minerals and
biological testing of soils can be thrown out because they become
irrelevant. The extraction methods currently in use and so often debated
(and too often creating confusion for the land manager)are purported to try
to emulate the water soluble nutrient uptake by the plant from the soil.
They are also a good way to support fertiliser sales and, in the confusion
that is created, to keep people from looking further for better ways to
manage the land resource.
Back in 1982, Lee Fryer wrote in his introduction to "The Bio-Gardener's
Bible" that the organic era of farming effectively ended in the early war
years when the chemical spoils of war enabled a 'revolution' in farming to
take place. From there the Petro-Chemical era would begin to decline in the
late 1990's and the biological era begin to have effect as contamination
issues related to ill health all the way up the food chain were beginning to
be understood. This is an exciting time, but each of us must ask whether
more of the same from the past is the way of the future for agriculture and
health of the environment and people, or whether it is time to learn from
nature's ability to recover from natural and man induced hostile
environmental episodes and actively make use of this learning.
Best regards,
Gerhard Grasser
"A man should farm as if he would live 1,000 years, but live as though he
were to die tomorrow."
-----Original Message-----
From: graze-l-admin@witt.ac.nz [mailto:graze-l-admin@witt.ac.nz] On Behalf
Of leon
Sent: Sunday, 16 April 2006 7:42 PM
To: graze-l@witt.ac.nz
Subject: [SPAM] - Re: [Graze-l] mineral mysteries - Email found in subject
In the discussion on fertilisers and mineral feeding, some refer to �Soil�
tests which are history and replaced with pasture tests by the most advanced
farmers and researchers 30 years ago.
The last soil test I did on our farm was in 1956 when I, like thousands of
others, could see it was useless.
Pasture Tissue Versus Soil Tests
Animals need pasture element levels to be as close to TMR levels as possible
so the first thing to do when 100% pasture farming is to find out the
element levels in your pastures and to fertilise to correct them as best you
can. Some minerals may still have to be fed. Trying to work out an accurate
and complete fertiliser mix from a soil test alone is impossible and soil
testing has very little application in animal nutrition. Elements in the
soil affect each other. By how much, depends on many factors such as
quantity of each, moisture, pH, soil types, texture, organic content, etc.
Pasture tissue figures are actuals that pasture has obtained from the soil
and what the animals are eating, so the antagonistic effects of elements in
the soil are bypassed. Pasture tissue figures are more like a video of what
is happening rather than a soil snapshot on one day which could be
influenced by many things.
Lime, magnesium, acidifying fertilisers, recent rain and moisture levels
change the pH. Checking it every four or five years is usually enough. Do it
in similar weather conditions, i.e., time of year and moisture levels. The
pH tells you very little about a soil. It doesn�t tell you what causes the
pH to be low or high. A pasture sample will tell you what causes the pH to
be high such as high calcium, high molybdenum or high magnesium. High
manganese in a tissue analysis sometimes indicates an under-drained acid wet
soil needing lime, however be aware that some soils are naturally high in
manganese. You should know the soil types on your farm. Low cobalt in
pasture indicates low organic matter, but not always. Very high cobalt in a
pasture analysis can be a result of soil getting into the pasture sample
from mud or dust.
Despite what some laboratories� claim, soil tests cannot measure some of the
trace elements accurately. Take one soil sample, mix it thoroughly, divide
it and send it to two labs (or even to one under two paddock names) and
you�ll realise that you�ve been cheated over the years you�ve been taking
them, not only in paying for an erratic system, but also for using it to
determine your farm�s main expenditure, i.e., fertiliser. I know NZ and USA
farmers who have sent identical soils to different labs and got widely
different figures and recommendations.
Even phosphorus, especially if reactive phosphate�s are used, nitrogen, or
even sulphur levels in soils are not measured accurately, and even if they
are, it is not what the plant is taking up or what the animal is eating.
Pasture tests correctly taken and analysed by good laboratories are
extremely accurate. Take a sample and divide it in two and send it to two
labs you�ll see.
Comparative figures from Winchmore Irrigation Research Station in the South
Island of NZ show tissue figures are more accurate. Their comparisons showed
that soil P levels take a while to drop after P application stops, whereas
tissue levels drop much sooner so are again a more accurate guide.
Regarding potassium, the US�Potash & Phosphate Institute, 655 Engineering
Drive, Suite 110, Norcross, GA 30092-2837, USA. Phone 770-447-0335, Fax
770-448-0439, wrote that soil K levels have decreased after applying K, but
tissue levels increased. Get their �There's More Than One Way To Recommend
Fertiliser,� Fall 1996, No. 7.
An NZ AgResearch article in April 1994 Dairying Today monthly stated that no
relationship has been determined between K soil tests and pasture growth in
peat, coarse textured ash and in pumice soils, so soil K figures should not
be used, pasture ones should. I believe that the recommended soil K figures
used in most countries are too high, hence, the high pasture levels and the
frequent animal health problems, especially metabolic ones and bloat.
Every year there are farmers who are puzzled by the differences in the
amounts of fertiliser recommended for field crops by different sources.
Although most people appreciate that soil testing is inaccurate, it is
perplexing for them to see recommendations from the same analysis that
differ by as much as several fold.
Wrong fertiliser recommendations waste millions of dollars in New Zealand
each year, mainly though not understanding fertilising, using soil tests,
sales people�s jargon (especially on some liquid fertilisers), and not
putting enough time and effort into working out the exact requirements. The
waste is also from low pasture yields and poor animal health because of
mineral imbalances and is likely to be the same in most countries.
In the USA, a soil sample was mixed then divided and sent to 69 different
laboratories. Fertilising recommendations made by each lab varied from 0
lbs/acre to 230 lbs/acre for nitrogen, and 0 to 150 for phosphate!
An NZ Rukuhia Soil Research Station technician could see that the plot
recommendations he was getting from soil samples he sent to the lab were
erratic. He divided a thoroughly mixed soil into six, and got six different
recommendations.
New Zealand laboratories seldom make fertiliser recommendations because they
realise that soil and/or pasture analysis can�t allow for all factors. A few
examples are -
? The farmer�s aims, such as maintenance, improving fertility, and even
taxation aims.
? High cost land warrants more fertiliser than low cost land.
? Type of livestock. Cattle require more copper than sheep. Dairying
takes more fertility off paddocks than beef.
? Livestock numbers per hectare. Heavy stocking may need more fertiliser.
? Pasture type. Most new improved pasture varieties require more
minerals.
? Rainfall. High rainfall and irrigation areas lose more through leaching
and grow more pasture.
So farmers should make their own fertiliser and mineral mixes using
information from VJ pasture analysis and fertiliser recommendations, etc.
Even with today�s knowledge of pasture analysing, on-farm fertiliser trials
are best for determining the optimum amount. Use a pasture analyses to
determine which elements to apply, and then do on-farm growth trials to
finalise the total quantity of growth elements to apply per hectare. Until
these results have been obtained use local knowledge to decide the total
quantity to apply per acre or ha.
NZ AgResearch have at last recognised that on farm fertiliser trials are the
best way to be sure that you are not over or under fertilising and they
developed farm trial kits to help do this.
The university of Saskatchewan developed a soil probe that measures the
amount of nutrients available for plant uptake called the Plant Root
Simulator; it uses special resins for absorbing soil nutrients in the same
manner as plant roots do. The probes are left in the soil for up to two
weeks, then removed and analysed. However, this system will still not show
exact pasture levels and what the animals are eating, only pasture analyses
do this.
Soil tests are usually taken from only the top 75 or 100 mm (3 or 4 inches).
Chisel ploughing can mix and bring up minerals from three times that depth
to the benefit of pastures (especially clovers). Generally, clovers grow
much better when subsoil has been brought up. Check areas where subsoil has
been brought up from ditch cleanings and where plants are growing in ditches
or where refilled trenches over pipes or cables.
Fertiliser trials
These can be the most profitable things you do on your farm. Firstly decide
which elements to try. Base this on local knowledge and pasture tissue
tests. A simple trial involves getting a small amount of the fertiliser and
spreading it at various rates on a representative part of the paddock,
preferably in line with a fence post and at right angles to a frequently
used lane where any differences can be observed while driving past. Decide
the rates to use and apply them on a two-metre wide strip five metres long.
This gives a ten square metre trial which is one thousandth of a hectare, so
the amount to apply is easily worked out. For example, if wanting to apply
lime at 2.5 tonnes/ha (1 t/a), 2.5 kg (5.5 lbs) is the amount to apply to
ten square metres (3.3 x 3.3 m or 80� x 200�). Mark the fence post with an
old ear tag, marker pen, nail, axe, knife or some other marker.
A thorough trial requires choosing two identical paddocks, applying
different rates on each whole paddock, then measuring yields before and
after grazing and/or counting the grazing days for two years. Accurate
measuring is essential for a thorough trial, so use a PastureGauge. It can
soon pay for itself if increased pasture production is obtained, or money is
saved on fertiliser.
Always write down the date and all details and draw a plan of each trial.
Place it in your �Bring up Monthly� file and/or your computer to remind you
to monitor the sites. Remember to record the fertiliser types, rates, dates
and paddocks. Yields are recorded by measuring before grazing and after
grazing, then adding the totals consumed for the year. If you gross
$2,000/ha and you increase pasture yields by 10%, then you have netted
$200/ha, less the cost of the fertiliser.
Arid areas which don�t use fertiliser can make mineral feeding suggestions
from the tissue results.
Reading pasture samples
When studying a pasture analysis, firstly check whether it is for sheep or
cattle. Then look at the date it was done because element levels vary with
the weather and seasons (See VJ Pasture Analysis). Relate it to the weather
at the time, because winters can extend into spring, when springs are late,
and springs can extend into summer, or continuous rain over summer can grow
grass like that normally grown in spring.
The next thing to look at is the iron content, because, if it is high (above
200 ppm) then it indicates that the pasture sample might have been polluted
with soil (it is hard to get 100% clean samples), which means that the
cobalt level will be higher than is the actual case, and manganese could
also be higher.
Next look at the nitrogen figure, which indicates the speed of growth of the
pasture. 4.5% indicates good growth, higher indicates faster growth and that
too much N was applied which will temporarily lower the tissue levels of
some elements. Beware of nitrate toxicity when N gets too high. Very low N
figures indicate slow growth, so P and some other elements will be higher
than normal, assuming everything else is equal. However, the slow growth
could be because of low P levels in the first place.
When reading the samples, one must realise that P is the most important
growth element in a grass and clover pasture.
Plants have varying levels of the various elements in different parts of the
leaves, stems and seeds. For example, leaf tips have more P, but less Ca, so
if only the tips of leaves are collected as in very short pasture, P could
be inaccurately high and Ca inaccurately low. So if sampling of very short
grass has to be done, allow for this when reading the figures. Another
example is that Mg levels are lower in young sappy pasture, but increase
with maturity.
Also, old leaves from very slow growing pasture can have a high P level, and
at seeding many leaf levels decrease as the elements move to the seed
because the leaves have finished their job and are ready to die.
VJ software programmes are available. They show, optimum element levels,
seasonal variations and fertiliser rates.
Vaughan Jones
37 Ellerslie Ave
Chedworth
Hamilton 2001
New Zealand
Ph +64-7-853-7555
Fax +64-7-853-7556
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