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NITROGEN: THE DOUBLE-EDGED SWORD

and organic nitrogen via mycorrhizal pathways is highly Weaning Off Nitrogen
energy efficient, closing the nitrogen loop, reducing nitrifi- The activities of both symbiotic and associative N-fixing
cation, denitrification, volatilization and leaching. bacteria are inhibited by high levels of inorganic N. In
Enhancing the Liquid Carbon Pathway other words, the more nitrogen fertilizer we apply, the less
We can utilize our understanding of the liquid carbon N is fixed by natural processes. For this reason it is vitally
pathway to restore natural fertility to agricultural land. En- important to wean your soils off high rates of inorganic
hanced carbon flow to soil—via plant root exudates—not N—but please do it slowly. Microbial communities gener-
only supports the biological fixation of atmospheric nitro- ally require around three years to adjust. Nitrogen inputs
can be reduced 20% the first year, 30% the second year
gen, but also activates the vast network of microbial com- and a further 30% the third year. In subsequent years, the
munities essential to the provision of minerals, trace ele- application of small amounts of inorganic N will help to
ments, vitamins and hormones required for plant tolerance prime the natural nitrogen-fixing processes. In addition to
to environmental stresses weaning off high rates of inorganic N, aim to maintain as
such as frost and drought much diverse year-round living groundcover in crops and
and resistance to insects and pastures as possible.
disease. Higher micronutri-
ent densities in plants also There is increasing recognition of the fundamental impor-
translate to improved nutri- tance of soil microbial communities to plant productivity.
tional value of food. How- Many biological functions are compromised by commonly
used agricultural practices but fortunately redesign of farm-
ever, if nitrogen is supplied ing practice is not difficult. The five basic principles for regen-
in an inorganic (fertilizer) erative agriculture discussed earlier in this Resource Guide
Photo by Jimmy Emmons Plant root exudates leaking out the liquid carbon pathway. have been proven to restore soil health and increase levels of
form, it will short-circuit
organic carbon and nitrogen. From these, farmers and ranch-
As a result, plant mineral
ers can build an integrated land management package that
densities fall and immune
suits their individual property and paddock needs.
function is reduced.
to feed soil biology.
More and more farmers around the world are discovering
Getting the Basics Right how to restore natural topsoil fertility by moving away from
It is now recognized that plant root exudates make a greater bare fallows to biodiverse year-long green plant cover, coupled
contribution to the formation of stable organic complexes with appropriate livestock management and reduced appli-
within the soil than does the above-ground biomass. But cations of inorganic nitrogen. Improvements to soil function
here’s the rub. The microbes essential to the stabilization deliver benefits both on-farm and to the wider environment.
of carbon require living groundcover and are inhibited
by high rates of inorganic N. Hence biological nitrogen
fixation and humification are rare in agricultural systems Photo by Christine Jones
where heavily N-fertilized crops are rotated with bare fal-
lows. Further, it has been shown that up to 80lb N/acre can
be volatilized and lost from bare fallows due to denitrifica-
tion in warm summer months. If green plants are present,
this N can be taken up and recycled, preventing irretriev-
able loss. When soil is bare there is no photosynthesis and
very little biological activity. Bare soils lose water, carbon
and nitrogen, nutrient cycles become dysfunctional, ag-
gregates deteriorate, structure declines and water-holding Healthy rhizosheaths on 8-week cereal rye seeded early fall without N.
capacity is reduced. The maintenance of bare fallows—or
the use of high rates of inorganic N in crops or pastures - By Christine Jones, Ph. D
A native of Australia, Christine has rapidly become one of
or worse, both—results in the uncoupling of the nitrogen the most sought after Soil Health speakers in the world and
and carbon cycles that have functioned synergistically for has been wildly popular on the United States Soil Health
speaking circuit. We count it a blessing to call her a mentor
thousands of years. and a good friend of Green Cover Seed.
For further information, visit www.amazingcarbon.com.

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