|February 13, 2004, organic-research.com/Elhuyar
Fundazioa: University of Navarre, Spain researchers have
designed a system for growing cereal crops that does not require fertilizer
or weeding yet produced yields twice that of its conventional counterpart.
The experiment, which took place on semiarid land, compared fields
that used neither fertilizer nor weeding and instead implemented an
alternating rotation of vetch and fallow, and a practice of returning
the straw to the soil after harvest with conventionally managed fields
using chemical fertilizers and herbicides.
In addition, researchers found that the higher yields of the ecological
system could be turned into a profitability of four times that of
the convention system when an organic market exists. The results
were presented in a PhD thesis by Gabriel Pardo Sanclemente of the
Public University of Navarre titled “The comparative study
of fertilization and weeding of the ecological cultivation of cereals
on semiarid land.”
The thesis is based on results from 26 tests carried out in various
semiarid land zones in Spain in which barley was grown with vetch
as a green manure and rotated with wheat and fallow. Experiments
were carried out comparing chemical methods of fertilizer application
and weeding with alternative organic methods.
The greatest profitability was obtained from the “ecological
system,” with organic fertilizer application and the mechanical
control of weeds. Following this was the “minimum system”
without fertilizer application or mechanical control of weeds. Trailing
behind and presenting the worst results in terms of profitability
was the “conventional system”.
In the wheat tests, the average production rates from the fertilized
and non-fertilized plots were practically the same. With barley,
the chemically fertilized plots produced on average 400 kg/ha more
than the organically fertilized ones, but this difference was not
It was found that the high levels of soil organic material and
initial phosphorus level were maintained after six years of testing,
even in the non-fertilized plots, but the level of potassium dropped
slightly. This suggests that the crop rotation used, together with
the returning of the crop residues to the soil, was sufficient to
maintain the initial levels of soil nutrients.
Regarding the weeding methods, both hoeing and the use of herbicides
did not increase the crop yields in the test conditions. Weed density
was, in general, poor on those cereal plots after the lying-in-fallow
or buried vetch period. The least density of weeds achieved after
any weeding treatment – mechanical or chemical – did
not give rise to any significant increase in grain production when
compared with the control.