are a relatively new tool in manís fight against weeds. Unlike
other pesticides, herbicides demand more skill in application.
Proper application is a very important aspect in herbicide use.
Due to improper application, herbicide treatment may be
ineffective or it can cause serious damage to crop in which it
was applied. For the safe and effective use of herbicides,
selection of proper equipment, techniques and methods are very
important. The following points should be considered while
Most of the
herbicides are applied in liquid form by various types of
sprayers. Under north eastern hilly region conditions, Knapsack
sprayers are quite suitable. It can be carried on the back with
the help of straps. It can be carried with a double action
lever-operated pump mounted either inside or outside container.
The operator operates the lever with his left hand and pumps the
spray solution, which moves through delivery pipe, held by his
important art of a sprayer. The flat fan and flood jet nozzles
are most suitable for herbicide application. The cone nozzles
should not be used for spraying of herbicides.
constant pressure throughout spraying is very important for even
spraying with minimum drift. For knapsack sprayer, pressure
range from 0.7 kg/m to 5 kg/m may be maintained.
important to prevent settling especially where suppressions of
wettable powder (WP) are used. Due to setting there may be
variation in concentration during spraying. The knapsack
sprayers are equipped with either mechanical or hydraulic
Avoidance of Drift
To avoid the
drift it is necessary to stop spraying when the wind is too
strong (maintains 10 km/hr). For a wind velocity of 5-10 km/hr
the height of nozzle may be maintained lower rather than usual.
Various types of shields (hoods) are used to prevent or limit
of sprayer is necessary for delivering the spray fluid at the
desired rate. Too much spray is not only waste the herbicide but
also has disastrous consequence on standing crop. On the other
hand too little spray fluid resulting in poor weed control. This
may results in wastage of herbicide, time and money.
sprayed per unit surface can be calculated by the following
unit surface =Discharge per unit time/Speed x Swath
depends on the number of nozzles, the size of the nozzles and
the pressure. It is important to have a uniform walking speed,
which can be achieved by regular practice. To get a constant
swath, the nozzle should always be maintained at the same
Any part of
crop or the soil must receive the same dose of chemical. If the
distribution is not uniform there may be risk of phyto-toxicity
to the crop or ineffectiveness against the weeds. Flood jet
nozzle given an even spray distribution.
the uniform coverage (i) the nozzles should be oriented so that
the spray jets from each nozzle will hit each other. (ii) The
height of the boom must be adjusted so that there is a 5 cm
clearly in between each spray jet.
At the end of
spraying the sprayer should be filled with water overnight to
prevent the herbicide from drying out and forming flakes that
ultimately may block the filter or nozzles. Some of the water
should be sprayed out to clean the nozzles and pipe. Next day,
the water should be sprayed out completely if this sprayer use
for applying the same herbicide. For application of other
herbicides it should be thoroughly cleaned out first by ringing
with water, then washing thoroughly with a detergent and ringing
again with water till no trace of detergent left. When sprayer
is used for spraying soil-based herbicide, a wash with kerosene
oil followed by detergent is useful.
Other important tips
recommended dose of herbicides.
follow instructions given for the use of particular
should be calibrated properly to find out matter required to
cover a hectare of land.
clean sprayer for herbicide application.
solution just before spraying.
spraying on windy weather. Be careful in applying near
susceptible crops. Avoid drift hazard.
selective in selecting herbicide for multiple cropping.
store herbicide solution for too long after mixing with water.
type nozzles are well suitable for herbicides application.
herbicides separately from seeds, fertilizer, insecticides and
20-30 lbs. air pressure per square inch is good.
empty container by burring down at least 18 inch deep in an
isolated area away from water supply points.
drains or flush spray equipment near source of domestic
for applying granular herbicides.
granular herbicides uniformly in 4-5 cm standing water.
herbicides should be done after draining the water from the
and phosphate type insecticides should not be applied 15 days
before or after the applications of propanil herbicides.
spray 2, 4-D herbicides before tillering stages of the drop.
for following levels for the safety purpose.