Sanet folks -
To add a bit to the ongoing discussion on microbial amendments and other
agricultural proprietary products, I urge you to look at an article I
wrote for the October 1999 Acres USA that discussed additional aspects of
using such materials. To summarize what the article said:
It is often hard to determine exactly how microbial amendments and
biostimulants work and whether they are indeed effective. Many
biostimulant products reputedly increase plant photosynthetic rate. If
indeed this happens, this change could cause the plant to produce more
carbohydrates which then could result in larger overall plant size, a
more extensive root system, an increase in yield and reduced disease
incidence, perhaps results in a different spectrum of rhizosphere
microbial life without actually adding microbial products. While this
sounds very positive, these effects can be subtle, often inconsistent and
highly influenced by environmental conditions - and not all products on
the market making such claims do indeed work. Using these products is
definitely not a substitute for excellent farm management and good soil
fertility maintenance - there are no magic bullets! They achieve their
best response with healthy plants growing on well-balanced soils.
Foliar fertility materials should be used only when soil tests, tissue
tests or foliar symptoms document an actual need. Many farmers find it
easiest to work with a skilled and reputable agricultural consultant who
can help them interpret test results and recommend appropriate treatments.
Microbial products present different challenges. For decades people have
tried to market microbes that were isolated from one location to be used
in vastly different environments. Microbes (especially beneficials)
adapt to their environment, much like plants do. They work well in a
familiar niche, but fail in others. For a mixed microbial product to be
successful, it would need to be formulated taking into account : 1) how
the organisms react among themselves, i.e. can they play and work
together; 2) can they survive in the same niche long enough to be
efficacious, i.e. do they enjoy the same food and can they withstand each
others waste; 3) are there additive effects that can cause phytotoxicity;
4) Potential carry over, i.e. some staying longer than welcome; 5)
displacement of other beneficials, especially native beneficials: (6)
whether they can survive in the presence of other typical applied
materials i.e. pesticides, fertilizers etc. Some microbial products on
the market do indeed satisfy these requirements, some do not. Also,
microbial products must be handled very carefully as soon as they are
manufactured until application. Because they contain living organisms,
if they are allowed to heat or dry out inappropriately at any time, if
they are applied after the expiration date or in combination with other
materials that may be toxic, many of the promised benefits may be lost.
Often proprietary products are promoted primarily with anecdotal or
testimonial advertisements. Most farmers do not accurately test these
products on their own farms and rarely are such materials subjected to
rigorous objective third-party testing. When farmers begin to use these
products, they should first use a controlled test to objectively prove
that there is indeed a beneficial effect. Often reputable companies will
provide technical assistance and free product if farmers are willing to
test in a way that will generate useful data. This would include
developing an experimental plan before application that clearly
identifies and marks the rows will receive the treatment and the rows
that will serve as an untreated control. Both areas should be large
enough to account for normal variation in the field. Throughout the
season, the plants in both sections should be objectively evaluated,
visually assessing the plant and root growth, response to stress, disease
and insect pressure, and general appearance. At harvest, the crop should
be weighed and the yields carefully compared. Only by using such a test
can a farmer really determine whether the cost of the material is
compensated by adequate yield increase, especially on lower value crops.
Based on such objective experimental information, then a farmer can
decide whether it would pay to use the product on more acres.
The current (April 2000) issue of Acres USA contains two additional
related articles that may be interesting to those wanting to learn more
about microbial amendments, one on Elaine Ingham's work with the Soil
Food Web and with compost and one on the use of Trichoderma-containing
products that can be used as seed and rhizosphere protectants (T-22
manufactured by Bioworks, Inc.). Elaine Ingham's web page is also full
of useful information and terrific illustrations (www.soilfoodweb.com).
The Northeast SARE program also has a publication on doing on-farm
research that contains helpful information about setting up appropriate
on-farm experimental trials (nesare@zoo.uvm.edu). Mary-Howell Martens
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