Mechanical management of weeds - Ecological Management of Agricultural Weeds - page 169

in systems where the growing season is long relative to the crop's develop-
mental requirements, and therefore the grower has flexibility with regard to
planting date. Despite its limitations, the false seedbed technique has broad
applicability.
Basic principles of mechanical weeding
This and succeeding sections discuss methods and implements for
physically removing weeds from crops. Most of these implements act by
cutting or uprooting the weeds with tools that disturb the soil. These imple-
ments are commonly referred to as cultivators . In addition to this large class
of implements, thermal and electric weeders damage weed tissues by a discharge
of heat, cold, or electricity.The most common of these are the various types of
flame weeders . Other implements include weed pullers and mowers . All these
implements may be classified according to where they work relative to the
crop row. Inter-row cultivators remove weeds from the area between crop rows.
In contrast, in-row weeders specifically attack weeds in the crop row. Near-row
cultivators and weeders may or may not affect weeds in the inter-row, but are
able to harm weeds closer to the crop row than is commonly the case for most
inter-row cultivators. Finally, some machines act similarly on both the in-row
and inter-row areas, and these are referred to here as full-field machines. Full-
field cultivators are usually used prior to or just after crop emergence. The
most difficult weeds to remove with cultivators and other types of weeders are
those that establish close to crop plants.Consequently,much of the discussion
will focus on implements that are effective against weeds in and near the crop
row.
Although this and succeeding sections focus on machine-powered imple-
ments,most of the principles governing cultivation apply equally to hand and
animal-powered tools. Also, many of the implements discussed in the follow-
ing sections,including inter-row sweep and shovel cultivators,rolling cultiva-
tors, basket weeders, and weeding harrows, have hand and animal-powered
analogs (Intermediate Technology Publications, 1985, pp. 12-55; Alström,
1990, pp. 98-131). Moreover, most in-row and near-row weeding tools are
simple, low-draught machines that could easily be mounted on an animal-
pulled toolbar. The low speed and fine position control possible with an
animal-drawn implement is ideal for these tools, and they could potentially
reduce some of the most arduous labor in the smallholder cropping cycle.
Even small increases in mechanization, such as a shift from hand hoeing to
use of a push weeder, greatly decrease weeding time (Tewari, Datta & Murthy,
1993), thereby improving the timeliness of weeding and crop yields.