Mechanical management of weeds - Ecological Management of Agricultural Weeds - page 173

the dark.Presumably,when tillage was performed in daylight,addi-
tional seeds were exposed to a light flash with each operation.
The optimum strategy for using light-sensitive weed germination
may be to perform primary tillage in the light,wait for emergence,and
then prepare and plant the final seedbed in the dark (Hartmann &
Nezadal,1990; Ascard,1994 a ; Melander,1998).So far,no studies have
reported on the effectiveness ofdark cultivation after planting.Aposs-
ible strategy for post-planting cultivation would be to perform shallow
full-field cultivations in the dark to minimize weeds in the crop row.
Early inter-row cultivation could then be done in the light to help clean
out the seed bank,since usually 100% ofyoung weeds in the inter-row
can be killed by subsequent operations.The final cultivation would then
be done in the dark or with light-shielded equipment to minimize
further emergence.
7. Attentive timing relative to changing weather and soil conditions can improve the
effectiveness of cultivation .Rotary hoes are ineffective when the ground is
too wet (Lovely,Weber & Staniforth,1958).Flame weeders work best
when leafsurfaces are dry (Parish,1990).Most cultivators are more effec-
tive during hot dry weather since,under these conditions,uprooted
weeds desiccate quickly without rerooting (Terpstra & Kouwenhoven,
1981).Thus,planning cultivation with the weather forecast in mind fre-
quently improves results.
Machinery for mechanical weeding
A cultivator consists of a frame and one or more types of tooling that
engage with the soil and weeds. Most commonly, cultivators are belly
mounted under the tractor or carried on a three-point hitch. Front mounting
is also possible for some implements.Belly- or front-mounted implements are
easier to guide and less prone to damage the crop because the driver can see
the position of at least one set of tools relative to the row and because small
changes in the tractor's direction do not cause large shifts in the implement's
position. However, wider, longer (to accommodate more tools), and higher-
clearance implements generally require a rear mount. Automatic guidance
systems and human-steered implements are discussed below.
A variety of tools are available for physical weed control. The amount and
type of information available on these implements vary greatly. For most
equipment, comparative data are meager, and some devices have received no
scientific study at all.Consequently, much of the information discussed in the
following sections is based on the personal experience of the author, or