(par 2.2.1. 6.2) Why Are Earthworms Important?

http://www.earthwormsoc.org.uk/earthworm-information/earthworm-information-page-3 Soil structure Earthworms have been called ‘ecosystem engineers’. Much like human engineers, earthworms change the structure of their environments. Different types of earthworms can make both horizontal and vertical burrows, some of which can be very deep in soils. These burrows create pores through which oxygen and water can enter and carbon dioxide can […]
(par 2.2.1. 6.4) Soil Properties

http://broome.soil.ncsu.edu/ssc012/Lecture/topic8.htm Physical Properties Features of the soil profile and the soil horizons are often described in the field in terms of the soil’s physical properties. Horizons are defined based on difference in the physical properties. Horizons differ from horizons above and below by some physical property. Soil physical properties affect the appearance and feel of […]
(par 2.2.1. 6. ) Soil Characteristics

http://www.vaderstad.com/en/knowhow/soil-basic The building blocks of soil The soil that is cultivated to create a seedbed only consists to half of solid material, while the remainder consists of pores filled with water or air. Of the solid material, clay and organic material have the strongest influence on the soil and determine its tillage properties. Soil consists […]