Weed Control
Overview
A weed is simply a plant growing where the farmer does not want it, and that is enough to make it an enemy of the crop. Weeds steal the same light, water, nutrients and root space the crop needs, so a field left unweeded can lose much of its yield long before harvest. Some weeds do worse still: the witchweed Striga actually attaches to the roots of maize and sorghum and feeds on the crop directly.
In this lesson you will meet a named local weed, learn how it harms a crop and how it spreads, and then work through the three routes a farmer can take to control it: cultural, mechanical and chemical. You will learn the difference between selective and non-selective herbicides, when each is used, and how to weigh up the cost, the labour and the risk of pollution so that you can suggest the right method for a given farm.
Objectives
- (a) identify one named local weed species of a crop and describe its harmful effects and the mode of spread.
- (b) explain methods of weed control including cultural, mechanical and chemical methods.
Audio Lesson
Listen to this lesson in the app
Mind map
This topic is mapped out so you can see how the ideas connect.
Open the mind map in the app
Flashcards
Quick recall practice on the facts this topic is tested on.
Practise these cards in the app
Lesson Note
Complete Note Available on the Green Bridge App
Get the Green Bridge CBT app on your phone or computer for the complete IGCSE library: past papers, mark schemes, mind maps, flashcards and audio lessons.
Lesson Evaluation
Congratulations on completing the lesson on Weed Control. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which of the following best describes a weed? A. A plant grown for food B. A plant growing where it is not wanted C. A plant that fixes nitrogen D. A plant resistant to herbicides Answer: B
- Striga is a serious weed of maize and sorghum because it: A. Only grows on paths B. Is a parasite that attaches to the crop's roots C. Improves the soil D. Cannot produce seeds Answer: B
- A herbicide that kills certain weeds but not the crop is described as: A. Non-selective B. Systemic C. Selective D. Contact Answer: C
- Which method of weed control is an example of cultural control? A. Hand hoeing B. Spraying a herbicide C. Crop rotation D. Ploughing Answer: C
- A systemic herbicide is more effective than a contact herbicide on a deep-rooted weed because it: A. Works only on the leaves B. Is cheaper C. Is carried through the plant and kills the roots D. Evaporates quickly Answer: C
Work through these questions in the app
Work through these questions in the app
Recommended Books
Practice Mock Questions
Want to practice mock questions on Weed Control? Download the Green Bridge CBT app to access mock questions and full practice assessments for this topic.
Download The App On Google Playstore
Everything you need to excel in your exams
