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Soil scientist Hans Jenny reminded us that soil was not a thing,
but a web of relationships. Rattan Lal, president of the Soil
Science Society of America, recently reaffirmed that insight in
an article he wrote for the Crop, Soils, Agronomy News.
Reflecting on our tendency to describe crop residues as “waste”
(especially in our current rush to use these residues for
ethanol production), Lal warned that this was
… a dangerous trend because crop residue
is not a waste. It is a precious commodity and essential to
preserving soil quality. In addition to controlling erosion
and conserving soil water in the root zone, retaining crop
residues on the soil is also necessary for recycling
nutrients, improving activity and species diversity of soil
micro- and macro-fauna, maintaining soil structure and tilth,
reducing nonpoint source pollution and decreasing the risks
of hypoxia in the coastal regions, increasing use efficiency
of fertilizers and other inputs, sustaining
biomass/agronomic yield, and improving/maintaining soil
organic matter content. (CSA News, Volume 52, No. 5,
May 12, 2007)
This comprehensive evaluation of the importance
of crop residues to soil health brings to mind the writings of
Sir Albert Howard, Lady Eve Balfour and J.I. Rodale who, over
half a century ago, lamented our simplistic soil management
methods. They argued that simply inserting a few nutrients to
achieve maximum production (what Howard called the “NPK
mentality”) was, in fact, a kind of “banditry.” Without proper
maintenance of health of the entire soil complex, the soil’s
“stored fertility” is plundered, and jeopardizes future
generations.
We have thus far largely avoided the fulfillment of such
predictions because we have used cheap synthetic inputs to mask
the effects of the loss of stored fertility in the soil (at
least so far as maintaining yields is concerned). As Leopold
observed, we have excelled at “land doctoring” but we have
invested very little into the “science of land health.”
Since the inputs that facilitate production with little regard
to soil health are derived from fossil resources, we may soon
find the predictions of Howard and others coming true. The
principal fossil resources that have created this productivity –
oil, natural gas and groundwater – are now in a state of
depletion, so it is imperative that we attend to the science of
soil health.
We know from extensive research that when soil is managed to
enhance soil quality, practices such as returning crop,
livestock and other residues (preferably composted) to the soil,
and crop rotations (particularly with green manure crops) will
improve soil health. Such practices reduce the need for
synthetic inputs and improve water absorption and retention,
which decreases the need for irrigation. Now more than ever it
is critical to reinvigorate the science of soil health if we
wish to maintain productivity in the face of serious resource
depletion. We have ignored soil health far too long.
The recent discussion by the Iowa State University Agronomy
Department about a possible new Soil Science Institute is not
only a great idea but a necessary one. Hopefully the vision of
the institute is focused on a science of land health.
Fred Kirschenmann
More about
a Soil Science Institute for Iowa |
