Soil Types, Composition, Texture And Temperature
Overview
Pick up a handful of soil and you are holding a mixture: mineral grains of different sizes, dark humus, water, air and a teeming population of living things. The balance of these parts decides everything that matters to a farmer, from how much water the soil holds to how easily roots push through it and how warm it is in spring. Two fields side by side can grow very different crops simply because one is sandy and the other is clay.
In this lesson you will learn to describe a soil profile, sort soils by the size of their particles into sand, silt and clay, and recognise the prized crumb structure that humus helps to build. You will compare sandy, loam and clay soils, list the constituents that make up any soil, and see why soil temperature can make or break a young seedling.
Objectives
- (a) describe soil profile in terms of topsoil, subsoil and underlying materials.
- (b) describe soil texture in terms of different sizes of soil particles, sand, silt and clay.
- (c) understand soil structure, including the importance of forming and maintaining a good crumb structure, the effects of humus and maintenance of organic matter in the soil, oxidation of organic matter and the loss of soil structure causing capping and soil pans.
- (d) describe different soil types (sandy soils, loam soils and clay soils) and their properties, including water-holding capacity and drainage.
- (e) outline soil constituents in terms of mineral matter, organic matter, air, water (free or gravitational water, capillary and hygroscopic water) and living organisms (bacteria, nematodes, fungi and earthworms).
- (f) understand the influence of soil temperature on the rate of plant growth, the danger of excessive heat to young seedlings and the danger of frost to some crops, and the methods of reducing the effect of extreme temperatures by mulching of seedbeds and shading of transplanted seedlings.
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Soil Types, Composition, Texture And Temperature. 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 soil particle is the largest? A. Clay B. Silt C. Sand D. Humus Answer: C
- Clay particles have a size of: A. More than 2.0 mm B. 0.05 to 2.0 mm C. 0.002 to 0.05 mm D. Less than 0.002 mm Answer: D
- Which soil type generally has the best balance of drainage and water-holding for most crops? A. Pure sand B. Loam C. Pure clay D. Gravel Answer: B
- The water held in the small pores of the soil and available to plant roots is: A. Gravitational water B. Capillary water C. Hygroscopic water D. Free water Answer: B
- A hard crust formed when heavy rain seals the surface of bare soil is called: A. A soil pan B. Capping C. A crumb D. Humus Answer: B
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