In assessing on farm soil quality indicators as part of my routine
consultancy operations root observation is one of my key indicators.
Generally speaking it is usually pasture species but sometimes it also
includes orchard and vegetable varieties.
In a pasture situation I look for the depth of rooting, whether the
roots have hit a hard pan structure, the amount of fine feeder roots,
the aggregation of the soil particles occurring around the rhizosphere,
the nodulation on the roots of legumes, and the colour of the nodules
when split open and whether their are any necrotic areas on the roots
indicating perhaps some disease problems.
Root examination goes hand in hand with other soil quality indicators
such as worm numbers, soil structure, aggregation, texture, bulk
density, weed occurances, soil arthropod numbers(in Australia such
things as termites, ants and beetles help to turn over organic matter
and provide aeration) and organic matter content judged on colour and
perhaps testing with hydrogen peroxide.
This information accompanied by a good soil analysis gives a pretty good
indication of the quality of soil. Let us not also forget that plant and
animal health observations also assist in determining if there are any
problems in the soil.
Chris Alenson
Organic Advisory Service
Organic Retailers & Growers Association of Australia
----------
From: joel b gruver[SMTP:jgruv@wam.umd.edu]
Sent: Saturday, 1 November 1997 2:48:pm
To: sanet-mg@shasta.ces.ncsu.edu
Subject: roots as indicators of soil condition
Hello to all...
I am freshly inspired in my thinking about soil quality
following
discussion with some of you at the ASA meetings in Anaheim.
Since returning to MD I have been pondering simple methods
for assessing soil physical condition...
If one starts with the premise that high quality soil optimizes
root development, then a logical approach to evaluating soil
quality is to
look at root development.
We all know that exhuming an extensive root system is time
consuming and tedious... and would not be an appropriate
rountine soil
test... but what about looking at root development at some point
early in
crop development... how about as early as emergence ?
I am aware of studies evaluating crop cultivars in terms of
rooting
characteristics but have soils ever been evaluated in terms of
their
effect on rooting characteristics (e.g. depth, architecture,
root:shoot
ratio) ...
What would the optimum phenological time for sampling be to see
soil effects on roots but minimize sampling time ? What crop
species would be best suited for a soil structure bioassay and
which root
characteristic would be simplest to measure yet be sensitive to
soil structural quality ?
I am planning to plant some seeds in intact 0-30cm soil cores
and
destructively sample after a minimum growth period... maybe at
emergence... or 1 week after emergence...
Looking forward to hearing your thoughts on any past studies
using plants
to bioassay soil structure or any recommendations for the
development of a
simple soil structure bioassay method.
I wonder how many farmers have dug up crop plants to look at the
roots ?
It is easy to tell whether active nodulation has developed
on legume roots.... what else can be quickly observed ??
Joel Gruver
Soil Quality Research
U of MD
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