Agriculture Reference
In-Depth Information
they are succulent and before they shed their seeds; the same is true for biennial
weeds. With perennial weeds the approach has to be dif erent, and normally they
will be much harder to control. Chemicals are applied with spray apparatus,
which ranges from simple knapsack sprayers to the more sophisticated boom-
type sprayers, and some products are incorporated in dry form into the soil.
In young orchards care has to be taken not to use certain herbicidal
products that can check tree growth by being absorbed through the root system.
In other cases, the small trees have to be protected from receiving the chemical
spray or drift, which can be absorbed by the green stem, branches and leaves
or cause severe burns in these young tissues, while in large trees this is not
normally a problem because of their woody bark. For young seedlings and newly
transplanted orchards, glyphosate, a systemic herbicide, may be applied by rope
wick or weed wipers saturated with a more concentrated herbicide solution and
wiped on the weed leaves. These applicators eliminate spray drift and can be
used close to the stem. Application of herbicides through the irrigation system,
known as herbigation, has been shown to be ef ective. An important aspect
with many herbicides is to know the time needed after application for them to
be absorbed; in many cases if it rains too soon after application, the product
will not have had a chance to be absorbed and it might be lost. Often morning
applications are done to avoid the afternoon and evening rains.
There are restrictions on herbicide use imposed by manufacturers and
government agencies, and all applicators must know the proper uses. Growers
who intend to export fruit should become acquainted with regulations of the
consuming countries governing the use of registered chemicals, residue levels
and other precautions. In organic production, no chemical herbicides are
normally allowed and only mechanical or cultural practices like cover crops or
mulching can be used.
The use of herbicides can be expensive, so a cost comparison has to
be made between spraying them over the whole surface and the system of
mowing between rows and cutting weeds back in the row with a machete or
the use of a hoe, or the mixed chemical-mechanical approach of applying a
herbicide in the rows and mowing between them. The mixed approach keeps
tree rows free of weeds using mulches or herbicides, or weed growth is kept in
check by hoeing or keeping weeds low with a machete or mowers. In the humid
tropics, the area between rows has either a legume or grass that is mowed
periodically. The approach used is a fi nancial decision and will depend on
the orchard size and fi nancial status of the grower. Weeding is an important
production cost component in orchard maintenance.
WIND BARRIERS
Wind can have several ef ects on fruit crops. Gentle winds help ventilate the
orchard and create a healthier atmosphere around the trees. They will also
