First 3-4 years after transplanting are crucial for the growth of
mango plants.
Application of organic manure and inorganic fertilizers, irrigation
at regular intervals and good sunshine results in the growth of a broad
spectrum of grassy and broad leaf weeds in mango orchards.
The major monocot weeds that occur in mango orchards are Cynodon
dactyion and Cyperus rotundus, and dicot weeds are Bidens
pilosa, Tridax procumbens and Phyllanthus maderaspatensis.
Usually, manual method of weed control is adopted at this time due
to young nature of mango plants by employing women labour.
They use small hand tools (Khurpi) for removing weeds in basins
and between rows of plants.
When the orchard comes of age, i.e., between 8 and 10 years, mechanical
method of weeding by using bullock drawn implements or motor run tractors
and tillers with special weeding tool attachments are employed for effective
weed control.
The type and nature of tools used in mechanical method depend upon
the row spacing adopted for mango orchards.
In the cultivation of mango orchards at least twice a year is necessary
to keep the weeds under check which otherwise may prove harmful to the
growth and productivity of mango trees.
In closely planted orchards, where ploughings becomes difficult, the
cultivation is done by hoeing with the spade.
In mango orchards, 15 to 20 years old, weed problems still exist and
the degree depends upon the variety grown and the row spacings given.
There are tall and dwarf varieties and intermediate ones.
The canopy arrangement differs in these varieties.
When trees are young, the sunlight received at the ground level is
more and this results in the growth of perennial grassy weeds.
As the tree grows, the canopy cover increases and shades larger area
beneath trees which is suitable for the growth of shade loving weeds.
In dwarf varieties, more sunshine is received around the trees and
this encourages the growth of grassy and broad leaf weeds compared to
tall varieties.
Similarly, infestation of mango orchards by weeds is closely linked
with row spacing, showing direct proportion between the two.
It is concluded that, for an average type of mango orchard, three
to four ploughings (machine or bullock drawn) are enough in a year.
Cover cropping is another practice followed in mango orchards to suppress
the growth of weeds, to bring additional income to the grower until
the trees begin to bear and to improve the health of trees if the intercrops
grown are of the right type.
Generally, cover crops are grown in space between the trees taking
due care that no crop comes under the spread of the trees so that roots
of the intercrops and the trees do not come into competition with each
other for drawing nutrients from the soil.
The recommended intercrops in mango orchards for summer season are
bottle gourd, bitter gourd, onion, chillies, cowpea, black gram and
green gram.
For winter season, the intercrops suggested are, peas, turnip, cauliflower,
carrot, radish and gram.
Herbicides have been used to some extent in mango to control weeds.
The good control of weeds in mango is possible with paraquat (3.0
kg a.i/ha).
The weed control in mango orchards for 24 weeks is done by using
diuron as pre-emergent treatment at 6.67 and 8.9 kg/ha.
Bromacil and dalapon were also effective for controlling dicot and
monocot weeds respectively.
The leaf nitrogen content in young mango seedlings can be increased
with fluchloralin when applied pre-emergent to weeds.
One spray of atrazine or diuron at 2.0 kg a.i./ha as pre-emergent
treatment to soil and one spray of paraquat as post-emergent spray on
weeds at 3.0 kg a.i./ha, six months after the soil treatment, to be
effective for controlling both monocot and dicot weeds for one year
in (one to five years old) mango orchards.