- One reason is to determine whether the right foodweb is present
and if it isn't present, what is needed to bring soil health back.
- Another reason is to determine the effect of a product or
management practice on soil foodweb organisms, specifically to
determine effects on total and active bacteria, total and active
fungi, flagellates, amoebae and ciliates, nematodes and mycorrhizal
fungal colonization of roots.
- Yes another reason is that there are areas that require little
maintenance, and areas that are continual headaches. These "headache"
areas are places where the foodweb is probably severely out-of-balance
and by getting the foodweb back into balance, fewer inputs will be
required. Sample the foodweb in the "headache" areas and compare to
healthy areas. The organism groups with significantly different
numbers than present in healthy areas tell you what is wrong,
indicating what you need to fix. If the unhealthy areas have the same
foodweb structure as the healthy areas, then one of two things is
indicated. Perhaps what appears to be healthy is actually about to
succumb to a problem. Alternatively, soil chemistry is incorrect for
the plant desired and needs to be fixed.
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| Sometimes the explanation is
not the foodweb, but lies in soil chemistry. If the foodweb looks fine,
but the grass is still not growing, then focus on chemistry. For
example, in an area where grass growth always seemed a bit weak, the foodweb didn't look terribly unbalanced, just slightly low bacteria and
protozoa numbers. Slightly low protozoa meant slightly low production of
plant-available N, and slightly low bacteria meant slightly low
retention of nutrients and low food for protozoa. But fertilizer had to
be put down constantly to get any plant growth. In checking the bacterial
community, it was noted that the bacteria present were actually actinomycetes, and were apparently not helping grass growth. The
question was then why? An investigation followed with the prior manager,
uncovering the fact that there had been a spill of copper-based pesticide
in that area previously. An analysis for Cu showed elevated levels. The problem was
a soil chemistry problem, which initial analysis of the foodweb did not
highlight.
With high levels of copper, or heavy metal, the typical engineering
solution is to remove the soil with high Cu levels and replace with
fresh soil. But the spot was small enough that two other choices were
possible: Leach the soil to get rid of Cu, or add enough organic matter
to dilute the Cu to the point that normal bacteria could grow. The
manager spread a
inch of compost on everything twice a year, and every month,
added a 1% sugar solution with a little urea to provide N to balance the
N-demand of the added sugar. About 6 months later, normal bacteria
started to grow. Protozoa numbers came back to normal, and the grass
started to grow like the rest of the area. After about a year, the
manager stopped adding sugar, and treated the area just like the rest of
the lawn. The chemical analysis still showed Cu present in the soil, but
the grass didn't notice because the copper was, apparently, not
biologically available.
Usually the foodweb will indicate problems, but understanding what
the out-of-balance foodweb means can sometimes be like playing
detective. What's causing the lack of bacteria, or lack of fungi? Is it
lack of food? Lack of the organisms even being there? Presence of a
toxic material? Can we degrade the toxic material by providing food to
organisms that will do the degradation? Is compaction preventing growth
because not enough air is getting into the system? Too wet or too dry?
This is where the role of the consultant becomes critical, because the
folks at SFI (testing facility) can't be out there on each course, turf
or landscape area. Together we work out the solution to each problem
encountered. We develop the "solved case" file, so when the same or
similar problem is encountered again, we have background information
that helps us solve the problem rapidly. |