I just want to share something that i've learn through my blog. Just in case anybody need some notes to study. Furthermore, it also help me to improve my English as well. I'm just doing some revision for the subject Principle of Weed Science, for Test 2.. :)
Weed in general are plants which grow where it is not allowed or wanted and interfere with human need and desire. There are several method that can be used to control the weed, but it is all depend on the situation, capability and environment of that area.
Here are the factors that infuencing to choose method of controlling :
1- Cost = we need to think about the expenditure, cost that we need to cover up
2- Availability of resources = For example the equipment needed, labour
3- Type or stages of weed = type refer to the narrow leaf or broad leaf, aquatic areas etc
4- Type or stages of crop = type refer to description to the crop, stage of growth and etc
5- Situation on the area = is it a landscape surface or moist, wet etc.
There are 4 method of controlling that i can list down
1-Physical or mechanically
2-Cultural
3-Biological
4-Chemical
PHYSICAL = "to injure or killing physically"
HOW- By doing this kind of controlling method, you have to use hands, machinery or any equipments.
WAYS - pull out derooting, to burn, to slash, to cut, to plough, and hoeing using equipment
CULTURAL = "involve agronomic practices and management"
HOW - manage between the crop and weed, agronomic activities before planting, while planting and after
WAYS - use clean seeds, plant cover crops example family LEGUMINOSAE, doing some mulching - to reduce water evaporate to the atmosphere, crop rotation - by doing this will change the environment for the growth of weed and cut down the life cycle, intercropping - using empty spaces example in between the ridge, high density planting system - use up and maximise the spaces, crop selection - it will provide the crops to compete each other.
BIOLOGICAL = "involve the usage of microorganisms as an agent"
HOW- apply it on soil or in the planting area
WAYS - select find characteristic of the microorganisms like :
*ability to kill or prevent reproduction of the weed
*ability to spread or search and also recognize weed. means that this organisms eat the weed only
not the crop
*adaptable means that these microorganisms have ability to adapt in certain area
*self reproduction - it has their own reproduction system and be able to regenerate themselves
Basic term before choose these controlling method :-
- host specificity
- synchronization of life cycle
- no changing of host
CHEMICAL = " using chemicals to kill or prevent the growth"
HOW- spray, put or apply these chemical to area that we want to kill
But there are pro and contra when using this method of controlling.
PRO - can use many types of chemicals
- it can reduce tillage of soil
- cheap, because many company got license to produce it
- fast and very effective
CONTRA - it can be source of misuse
- source of pollution, if excessive happen
- can be direct source of danger , to human
2 Source of MISUSE happen when :-
- ignorant of the chemical activity
- careless during use
There are the factors that will causing misuse:-
1-wrong dosage = the concentration is too high or too low
2-wrong chemical = using wrong material example like for broadleaf and narrow leaf
3-failure to do the caliberation = between the chemical
4-the equipment is not proper use = maybe the sprayer and the container, or miss to put the filter inside the tank
5-condition not suitable = raining or wind
Danger from MISUSE causing :-
- toxicity or poisoning (to human)
- residual pollution (excess in the chemical turn to pond and etc)
- drift (by wind)
TOXICITY CLASSIFICATION is based on LD50 concept
LD= Lethal Dosage (killer dosage)
50 = 50% of the exposed population to the lethal dosage
For example, if LD50 20 mg/kg as A, and LD50 2mg/kg as B, the B solution is more dangerous compared to A because it only need 2mg/kg to exposed 50% of the population to the Lethal Dosage.
Types of herbicide
based on application
1- Pre emergent VS Post emergent
2- Contact VS Systemic
3- General VS Selective
pre emergent = apply before weed germinate
post emergent = apply after or while weed germinate (seed growth)
contact = kill only where its touch to the herbicide
Herbicide Classification
1- SELECTIVE = kill specific weeds without affecting other weed or crops
2- NON SELECTIVE = kill all plants, active on specific species, through placement
Mode of activity based on 4 ,
1-Contact = kill at where its placed, affect on annuals, require wetting the whole plants
2-Systemic = absorb into plant, need good coverage, transported in plant system, can be used to perennial
3- Time of using = Pre planting (before crop planting), Pre emergent (after planting - before crop / weed germinate), Post emergent (after crop/ weed germinate)
4- Treatment area/ Placement = Band (along the row between ridges), Broadcast (covering the whole area), Spot (cover limited area only), Spray (direct to weed)
Thats all from me. it is refer from the lecturer given by PM. Dr. R.
