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Johnsongrass
(Sorghum halepense) is the most troublesome weed on Grabov Rat. It
spreads aggressively by underground stems (rhizomes) and can form
dense colonies, displacing cultivated plants and restricting tree
seedling establishment. Most of the rhizomes are in the top 20 cm
of the soil profile, but some go deeper than 40 cm; over a tonne
of rhizomes and roots could develop on one acre of land.
Mechanical control of new rhizome production must be implemented
within the first month after shoot emergence. |
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The
chief agent of anthropogenic (man-influenced) transfor-mation of
the land has been agriculture. By its very nature, it is an
intrusion and hence a disruption of the environment, as it
replaces a natural ecosystem with the artificial one, established
and maintained by man. The moment a farmer delineates a tract of
land, separating it from the contiguous area by arbitrary
boundaries and establishing it as his field, he is in effect
declaring war on the pre-existing environmental order. Wishing to
grow a particular crop (which may be of a species or a type not
indigenous to the area, and therefore incapable of establishing
itself there on its own), the farmer must now treat all the native
species as noxious weeds or pests, to be eradicated by all
possible means. However, in an open environment the wild species
continue to reinvade their stolen domain, so the farmer’s war is
never finally won.
The
constant effort to prepare the field for seasonal planting and to
eradicate weeds has traditionally involved repeated cultivation of
the soil, often leading to excessive pulverization and compaction.
Such mechanical manipulation tends to destroy the soil’s natural
aggregated structure and to render the soil surface particularly
vulnerable to erosion. |
Johnsongrass
(Sorghum halepense) |
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Daniel
Hillel: Out of the earth, Civilization and the life of the soil,
University of California Press, Berkeley, 1991. |