Visualizing Environmental Science

312 CHAPTER 12 Mineral and Soil Resources

erosion, breaking down toxic ma-

terials, and cleansing water.

Essential nutrient miner als

such as nitrogen and phos phorus

are cycled from the soil to organ-

isms and back to the soil again.

Decomposition, another ecosys-

tem service, is part of nutrient

cycling (ˆ}ÕÀiÊ£Ó°£{; also see Chapter 5). Bacteria and

fungi decom pose plant and animal detritus and wastes,

transforming large organic molecules into small inor-

ganic molecules, including carbon dioxide, water, and

nutrient miner als; the nutrient minerals are released

into the soil to be reused. Non living processes are also in-

volved in nutrient cycling: The weathering of the parent

material replaces some nutrient minerals lost through

erosion or agricultural practices.

nutrient cycling

The pathway of

various nutrient

minerals or elements

from the environment

through organisms

and back to the

environment.

ÕÌÀˆi˜ÌÊVÞVˆ˜}ÊUʈ}ÕÀiÊ£Ó°£{

In a balanced ecosystem, nutrient minerals cycle from the soil to
organisms and then back to the soil.

Elements

incorporated

into organic

matter in

animals

Organic

matter

moves into

soil

Decomposition

Minerals freed and

available to plants

Plant roots

absorb

minerals

from soil

Elements

incorporated

into organic

matter in

plants

1. How do weathering processes affect soil
   formation?


2. What are soil horizons?


3. What role do soil microorganisms play in
   nutrient cycling?


4. Define sustainable soil use.


5. Explain the impacts of soil erosion on plant
   growth and on other resources, such as water.


6. Identify and summarize the major soil
   conservation methods.

oil is as important as air and water for hu-

man survival. Yet humans disrupt soil sys-

tems that would be balanced— functioning

normally—in nature. We have had a harmful

Soil Problems and Conservation

LEARNING OBJECTIVES

S

impact on soil resources worldwide, particularly by in-

tensifying agricultural use. These human activities of-

ten cause or exacerbate soil problems such as erosion,

mineral depletion, soil saliniza-

tion, desertification, and soil

pollution, all of which occur

worldwide. Such activities do not

promote sustainable soil use.

Soil used in a sustainable way re-

news itself by natural processes

year after year.

sustainable soil

use The wise use

of soil resources,

without a reduction

in the amount or

fertility of soil, so it is

productive for future

generations.