Week 3 - Soil Structure & Organic Matter

Question 1

Explain the role of organic matter in the provision of nutrients for plant growth.

Answer 1

• Organic matter provides a store of nutrients which are important for plant growth. While nutrients especially N, P, and S are bound up in the structure of skeleton of organic matter they are not immediately available for plant uptake but they are not prone to loss from soil by leaching. They can eventually be released for plant uptake.
• Not only are nutrients bound in the chemical structure of organic matter, they can be retained by attraction to the surface of organic matter.
• Organic matter provides ‘energy’ for soil microorganisms. Without these organisms, nutrients would not be released from organic matter into plant available forms.

Question 2

Based on the graph, describe why the differences in total and fresh decomposing organic matter exist.

Question 3

Based on the trends shown in the graph, describe the implications of future plant growth.

Question 4

List and briefly explain the functions of organic matter in soil.

Question 5

What factors of cultivation contribute to the damage of soil structure?

Question 6

Define the two types of structural breakdown due to water.

Question 7

Describe in detail how you would determine if a soil is structural stable.