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Johnson grass (Sorghum halepense)

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.

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 farmerís 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 soilís natural aggregated structure and to render the soil surface particularly vulnerable to erosion.

Johnsongrass (Sorghum halepense)

Daniel Hillel: Out of the earth, Civilization and the life of the soil, University of California Press, Berkeley, 1991.

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