Classification of Herbicides

Question 1

What are the classification of herbicides based on chemical nature

Answer 1

Inorganic herbicides and organic herbicides

Question 2

What are inorganic herbicides

Answer 2

Inorganic herbicides were the first chemical used for weed control and they do not contain carbon atoms. They are made up of salts and acids

Question 3

Mention examples of inorganic herbicidal salts

Answer 3

sodium arsenate and sodium chlorate

Question 4

Mention examples of inorganic herbicidal acids

Answer 4

arsenic acid , arsonous acid and sulphuric acid

Question 5

What are Organic herbicides

Answer 5

Organic herbicides are herbicides that contain Carbon atoms, when their molecular structure contains carbon and hydrogen they are called hydrocarbons. They are derived from fossil fuels and they are of the oil and non-oil type. Though the non-oil type is more common these days. eg of oil ones are diesel oil and aromatic oils. We have a total of 150 organic herbicides available.

Question 6

What is the classification of herbicides according to the target site.

Answer 6

Soil-active herbicides and the foliar active herbicide.

Question 7

What are soil active herbicides. Explain thoroughly

Answer 7

Soil active herbicides are applied to the soil and not the already grown plant, they help to stop the germination of the weeds from inside the soil and also inhibit the growth of their stolons, rhizomes or tubers. Depending on the rate and the type of herbicide used , soil active herbicides can control weed for about 4 -8 weeks. They are usually added to the soil at the time of planting. For already established crop lands they are applied to the weed free inter-rows of the crops. For bareland that are not for crops ie non-crop lands, soil active herbicides are used as soil sterilants and fumigants.

Question 8

Mention the methods of application of soil active herbicides

Answer 8

Surface application
Sub-surface application
Band application
Herbigation
Soil fumigation

Question 9

Describe the surface application of soil active herbicide

Answer 9

This is when the herbicide is applied uniformly on the surface of the soil either by spraying or broadcasting. These herbicides can be incorporated into the soil or they can be left like that on the surface undisturbed. The reason they should be incorporated is to avoid volatilization or photo - decomposition

Question 10

Describe the sub-surface application of herbicide

Answer 10

This is the application of herbicide in a concentrated band about 7 - 10cm below the soil surface.

Question 11

Describe the band fertilizer application

Answer 11

This is the application of herbicide in a band along the crop - rows and not the inter-rows. This method is beneficial because it helps you focus on where weeds will affect and have the most impact on the plant and by that way you do not get to use too much herbicide you’re able to save and conserve the money to purchase the herbicide

Question 12

Describe the soil fumigation method and how are fumigants applied to the soil.

Answer 12

Herbicides used for fumigation are called fumigants and depending on the nature of the soil fumigant,they can be applied in three ways.
- By injection(chloropicrin)
- By releasing under sealed plastic covers (methyl bromide)
- By direct soil surface application(metham)

Question 13

Describe Herbigation

Answer 13

This is the application of herbicide through irrigation water , it could be surface or sprinkler irrigation.

Question 14

What are foliar active herbicides

Answer 14

They are herbicides that are applied when the weeds have already emerged from the soil. The herbicide is absorbed by the foliar(leaves) and is then translocated to other parts of the plant.

Question 15

Examples of soil-active herbicides

Answer 15

simazine, alachlor, trifluralin, EPTC

Question 16

Examples of foliar-active herbicides

Answer 16

paraquat, diquat, 2,4,5- T,herbicidal oils.

Question 17

Examples of herbicides that are both soil active and foliar active

Answer 17

2,4-D , picloram and atrazine.

Question 18

Mention the methods of application of foliar active herbicides

Answer 18

Blanket method
Directed spraying
Spot treatment
Protected Spraying

Question 19

Describe blanket application

Answer 19

This is when the herbicide is applied uniformly to standing crops without minding the location. very highly selective herbicides are used for this process so that it doesn’t harm the desired plants at all

Question 20

Describe Direct spraying application

Answer 20

This is when herbicide is applied to the weeds found on the inter-rows of crops. The perk here is that the farmer has to make sure that the desired crops have grown tall and above the weeds, so it will be easier to spray on then and not damage the foliar of the desired crop. It is mostly used in orchards and plantations

Question 21

Describe Spot-treatment

Answer 21

This is applying herbicide to patches of small weeds and leaving the weed free area, it is used to kill noxious, perennial weeds with potent herbicide. It helps to save herbicide because you only applly it to the areas affected.

Question 22

Describe protected spraying

Answer 22

This is when you try to achieve selected herbicide spraying using non-selective herbicide on distantly planted vegetables. You should cover the desired plants with metal sheets or plastic sheets or use a hooded sprayer to spray the herbicide , this way you get to control where the non-selective herbicides get to.

Question 23

Describe protected spraying

Answer 23

This is when you try to achieve selected herbicide spraying using non-selective herbicide on distantly planted vegetables. You should cover the desired plants with metal sheets or plastic sheets or use a hooded sprayer to spray the herbicide , this way you get to control where the non-selective herbicides get to.

Question 24

Describe protected spraying

Answer 24

This is when you try to achieve selected herbicide spraying using non-selective herbicide on distantly planted vegetables. You should cover the desired plants with metal sheets or plastic sheets or use a hooded sprayer to spray the herbicide , this way you get to control where the non-selective herbicides get to.