Chapter 37, Problem 1IQ

Describe the characteristics of a fertile soil.

Summary Introduction

To describe: The characteristics of fertile soil.

Introduction: Soil is a dynamic and natural system that is crucial for the sustenance of humanity. In the global ecosystem, soil performs five critical functions. This includes it acts as a medium for the growth of the plant, it regulates water supply, acts as a habitat for soil organisms, and raw materials recycler. The most important function of the soil is to store and supply essential nutrients to plants.

Explanation of Solution

Characteristics of fertile soil:

Soil texture:

Soil texture is considered as a unique property of the soil. Soil texture has a profound effect on the behaviour of soils, like nutrient retention, water holding capacity, nutrient supply, drainage, and nutrient leaching. Topsoil is the mixture of various mineral particles from the rock, for example, humus (decomposing organic matter) as well as living organisms.

Loams:

Loams are composed of equal parts of sand, clay, and slit. Loams are often considered as the most fertile soils. It encloses fine particles to offer a large surface area in order to retain water and also minerals. Moreover, sufficient coarse particles provide air for the roots to respire.

Topsoil composition:

In soil, the positively charged ions, namely K⁺, Mg²⁺, and Ca²⁺ stick to the negatively charged surfaces of soil particles. Hence, they are not easily lost by leaching process (filtration of water through the soil). During cation exchange, the hydrogen ions displace the positively charged mineral ion from soil particles, thereby making the ions easily available for absorption. Soils that possess more clay and organic matter have a higher capacity for cation exchange. However, negatively charged ions like sulfate (SO₄^2-), phosphate (H₂PO₄^­­-), and nitrate (NO3-) tend to leach away more rapidly.

Humus:

Humus is a dark, organic component that builds a crumbly soil. Humus retains water, supplies mineral nutrients, and provides good aeration.

Soil inhabitants:

Soil inhabitants like bacteria, algae, fungi, protists, worms, insects, and nematodes affect the physical as well as chemical properties of the soil. For example, bacteria enrich the soil with nitrogen and phosphorus and thereby improve the texture and quality of the soil.