Lesson 28. Weeding equipment: power operated and manual Row crop cultivation equipment
Weeds are robbers and a farmer has to destroy them to save his crops. Control of weeds and grasses are most labour and time intensive operations in the production of crops.
Methods of controlling weeds:
1) Mechanical cultivation or shallow tillage:
- Most economical
- Weeds are uprooted, covered or cut-off- Killing weeds and grasses in rows is major problem
2) Selective burning or flaming used for controlling weeds in the rows. (Flame weeding)
3) Chemical herbicides are used in various stages of crop planting and growth.
- Selective herbicides like 2, 4D used to kill broad leaf plants and do not injure grasses. Similarly Dala Pon kills grasses and does not injure broad leaf plants.
- Pre-plant and pre-emergence applications are incorporated in the soil, in bands of 18-25 cm.
- Post-emergence application of herbicides is also used. Adequate moisture is required to activate the soil-applied herbicides.
- Direct post-emergence general contact weedicides are used in row-crops.
4) By spreading plastic sheets between rows treatments are applied to soil surface in conjunction with planting operation (behind press wheel).
5) Control of weeds by shading crops.
6) Hand-hoeing & finger weeding.
- Weeds in inter-row spacing are controlled by cultivation and those in rows by one or more methods.
- For inter-row cultivation equipment used are cultivators, sickle, wheel hand hoe, triphali.
1) Inter culture the fields
2) Destroy weeds in the fields
3) Aerate soil for proper growth of crops
4) Conserve moisture by preparing mulch on surface
5) To sow seed when provided with sowing attachment
6) To prevent surface evaporation and encourage rapid infiltration of rain water into soil.
I) On the basis of type of tool
a) Disc cultivator – fitted with discs
b) Rotary cultivator – fitted with tines or blades mounted on power driven hori shaft.
c) Tine cultivator – fitted with tines having shovels
II) On the basis of power used
a) Tractor drawn
b) Animal drawn.
a) Trailed type:
- Consists of main frame which carries a number of cross members to which tines are fitted.
- At forward end hitch arrangement is provided for hitching.
- A pair of wheels is provided.
- Tines in each row are spaced widely to allow free passage of soil and trash around them.
- The depth of working is set roughly by adjusting tines in their clamps.
b) Mounted type:
i) Spring loaded tynes.
- Tines are hinged to frame and loaded with spring so that it swings back when an obstacle is encountered.
- Each tine is provided with two heavy coil springs, pre-tensioned to ensure minimum movement except when an obstacle is encountered.
- Springs operate when points strike roots or large stones to prevent damage of implements.
- As obstruction passes tines are automatically reset.
- Tines are made of High Carbon Steel.
- This type is particularly recommended for soils which are embedded with stones or stumps.
- Gauge wheel provided for controlling depth.
ii) Rigid tynes:
- Tines do not deflect during work in field.
- Tines are bolted to frame.
- Spacing of tynes is changed by slackening the bolts and sliding the braces.
- As rigid tynes are mounted spacing is adjusted easily.
- Gauge wheel provided to adjust depth.
b) Animal drawn
- Mostly three tines cultivator with seeding attachment.
- Also used for secondary tillage.
- Also used for intercultural of row crops.
Duck – foot cultivator:
- Rigid type tractor drawn used for shallow plowing, destruction of weeds and retention of moisture.
- Sweeps are attached to rigid tines.
- Sweeps are made up of high carbon steel.
- Size is 225 cm long, 60 cm wide with 7 sweeps.
- For actual cutting of soil different types of shovels and sweeps are used.
a) Single point shovel
b) Double point shovel
c) Spear head shovel
- Rotary hoes are used with or without sweeps in combination.
- Powered rotary cultivators are used for weed control and shallow mulching in crops which are closely spaced in line vegetables.
- Rotary cultivator if provided with suitable shields can be used extremely close to young plants having small root system.
- Control of unwanted vegetation by flaming is practiced since 1940.
- Flaming is used for thick – stemmed row crops, also for weeding around trees.
- It is important to control the flame path with respect to ground surface in rows.
- It is done when weeds and grasses are not over 25-50 mm.
- Heat intensity (fuel rate) and exposure time are adjusted to cause expansion of liquid in plant cells and consequent rupture of cell wall but not excessive heat to cause combustion.
- Effect of flaming becomes visible after several hours of flaming.
- Forward speed 4.8 – 6.4 km/hr for flaming.
- Cotton is well-suited. Other crops like corn, grain sorghum & soybeans whose stems are not injured by short exposure to an intense heat.
Components of flame weeder:
- Burner operates on LPG. Two types are used:
a) Liquid burner or self-vaporizing type
b) Separate vaporizer connected to tractor engine cooling system
- Fuel rates 7.5 – 15 l/h per burner- Well designed burner should produce broad, thin flame that is steady and well controlled.
- Burners for flame weeding are supported on skids hinged to a rear-mounted tool bar or on 11 – link arrangements having gage wheel.
- In combined flaming and cultivating operations burners are attached to independently gaged cultivator gangs.
Burner Placement and Flaming Practices:
- Optimum burner placement is influenced by type and size of crop and type of burner.
- Burner should set at 450 and flame should strike the ground about 50 mm from row centre.
- Parallel flaming can be used for small plants and crops with low resistance to flaming.
- Burners are placed to row on each side 75-125 mm from row centre in 11 flaming. Burner outlets are 100 – 150 mm above ground surface and directed downward at 450 towards rear.
Water spray shields for flaming:
- Water spray shields are developed which cause a drastic reduction in air temperature above spray, and increase versatility of planning.
- Conventional fan spray nozzles are used.
Thinning of crops like cotton is required to increase yield.
- Mechanical devices
- Manual or hand thinning is selective operation but tedious, costly and require high labour.
- Mechanical or chemical thinning may be either random or selective.
- Mechanical thinning done with row thinners and by cross thinning m/cs operated across the rows.
- Cross thinning done by cross cultivation with sweeps, knives etc.
- Chemical or flame thinners have metal boxes at regular intervals on wheels or conveyor. These cover the blocks or spaces to be skipped while flame or chemical spray is applied continuously along rows. These thinners have been employed only to a very limited extent.
Selective Mechanical or Chemical Thinning:
Electronic sensors which detect first plant occurring beyond the pre-selected minimum distance from preceding plant that was retained.
These sensors control knives or chemical spray in such a way that intervening plants are killed and selected plant is saved.