Agriculture Reference
In-Depth Information
Nitrogen is a critical limiting mineral nutrient in plant growth. Carbon and oxygen
are also critical, but are easily obtained by plants from soil and air. Even though air
is 78% nitrogen, atmospheric nitrogen is nutritionally unavailable because nitrogen
molecules are held together by strong triple bonds. Nitrogen must be 'fixed', i.e.
converted into some bioavailable form, through natural or man-made processes. It
was not until the early 20th century that Fritz Haber developed the first practical
process to convert atmospheric nitrogen to ammonia, which is nutritionally
available.”
http://en.wikipedia.org/wiki/Haber_process
The source of the N
2
is the atmosphere; the Hydrogen needed, as well as the
source of heat, has traditionally come from methane, i.e. natural gas. Under high
temperature and extremely high pressure (200+ atmospheres) the gaseous
mixture of Nitrogen and Hydrogen is repeatedly passed over a bed of metallic Iron;
the iron works as a catalyst to chemically bond the N and H, forming NH
3
,
ammonia.
Surely everyone has heard of “petroleum based fertilizers”? In reality, the
Haber-Bosch process is the only industrial fertilizer process that has any
“petroleum” connection, and that's a stretch, calling methane from natural gas
petroleum.The refining processes for Phosphorus and Potassium fertilizers use no
hydrocarbons.
Does “synthetic” N kill soil life? It can, when misused and overused. Probably the
worst example is 'knifing' anhydrous ammonia into the root zone of maize/corn.
While that can give a quick boost in growth and yield, the high dose of ammonia
kills off most soil life, while burning up humus at the same time.ArdenAndersen
(
Science in Agriculture
) writes that injections of anhydrous ammonia were used in
WWII in the Pacific to quickly turn jungle soils into hard-packed landing strips for
aircraft.
On the other hand, adding a small amount ofAmmonium sulfate to compost piles
or to the soil can greatly accelerate microbial action in breaking down organic
matter into stable humus. Both nitrate N and ammonia N occur naturally in all
agricultural soils. We are aware of no evidence that there is any chemical
difference between naturally occurring and industrially produced ammonia and
nitrate.
ANew Ecologically Sound Process for “Fixing”Atmospheric N
30 January 2013
Researchers from the University of Strathclyde and the University of St. Andrews have
demonstrated that ammonia can be synthesized directly from air (instead of N2) and H2O (instead
of H2) under a mild condition (room temperature, one atmosphere) with supplied electricity which
can be obtained from renewable resources such as solar, wind or marine.….their process could
also reduce the pressure on renewable energy storage, they note.
