Introduction

• Herbicides are chemical substances used to kill, suppress, or control unwanted plants (weeds) in crops, pastures, or fallow lands. They form a key component of chemical weed management.

Advantages of herbicides

a. On weed control

• They kill unwanted plants.
• They are easy to use
• Herbicides can be used on closely planted crops where other methods cannot be used.
• Most of the time one application of the herbicide is enough whereas other methods have to be continually used.
• They work fast. They can be removed quickly in critical situations.
• Herbicides are relatively cheap, and most of the time cheaper than manual weeding.

b. On crop growth

• They can destroy plants bearing diseases
• They help the crops grow by destroying the weed that causes harmful effects which include competition for water, nutrients and light; interference of weeds with crop growth by the release of toxins; modification of soil and air temperatures and the harboring of pests.
• They can be safely used as the manual and mechanical removing of weeds can destroy the crop.

c. Others

• They are relatively safe on lands which may erode.
• Non-selective herbicides can effectively clear fields, where houses and roads can then be built.

Disadvantages of herbicides

a. Effects of Herbicides on environment:

• Heavy dose of herbicides affect microbial population of the soil. With herbicides targeting amino acid synthesis in both plants and microbes, there is a possibility that N2 fixation may be inhibited by the application of certain herbicides.
• When these pesticides and herbicides contaminants dissolve in storm water they infiltrate the groundwater and then the surface waters, such as ponds, streams, rivers and lakes. These chemicals may also find their way into the soil and deeper groundwater units polluting them.
• Herbivores may eat the plants treated with herbicides and then carnivores eat the herbivores. The toxic herbicide would be passed up the food chain increasing in concentration each time resulting in cancers and even deaths.

b. Effects of Herbicides on Human

• Pesticides and herbicides can cause a number of health problems such as heart congestion, lung and kidney damage, low blood pressure, muscle damage, weight loss and adrenal glands damage.
• Arbitrary and indiscriminate usage of herbicides and pesticides can result in endometriosis, a common cause of infertility in women.
• Herbicides and pesticides have been suspected by the National Cancer Research Institute as a probable cause of certain cancers (i.e., cancers of the brain, prostrate, stomach and lip, as well as leukemia, skin melanomas, etc.) especially among farmers.

c. Effect of herbicides on crop plant

• If herbicides are not used properly, damage may be caused to crop plants, especially if too large dose is used, or if spraying occurs during a time when the crop species is sensitive to the herbicide.
• Unintended but economically important damage to crop plants is sometimes a consequence of the inappropriate use of herbicides.