Page 53 - Soil Degradation, Conservation and Remediation

38 1 Soil Resources and Soil Degradation

Lal ( 2009 ) proposed ten “laws of sustainable soil management.” The laws are
summarized below:
(1) Soil resources are unequally distributed among biomes and geographic
regions. Highly productive soils are located in favorable climates and are highly
populated and are converted to managed ecosystems, such as croplands, pasture, for-
est, and energy plantations. (2) Most soils are prone to degradation by land misuse
and soil mismanagement. Desperate actions of resource-poor farmers, smaller land-
holders, and greedy, shortsighted lust for quick economic returns by humans lead to
soil degradation. (3) The way how the soil is managed affects soil erosion and decline
in soil quality by other degradation processes. Restorative and recommended soil and
water management practices may retain productive potential of farming systems.
Judicious management of on-site and off-site inputs is needed for sustainable use of
soil. Indiscriminate and excessive use of tillage, irrigation, and fertilizers can aggra-
vate soil degradation. (4) The rate and susceptibility of soil to degradation increase
with increase in mean annual temperature and decrease in mean annual precipitation.
All other factors remaining the same, soils in hot and arid climates are more prone to

degradation and desertification than those in cool and humid ecoregions. (5) Soil can
be a source or sink of greenhouse gases, CO 2 , CH 4, and N 2 O, depending on land use
and management. Soils are a source of radiatively active gases with extractive farm-
ing which create a negative nutrient budget and degrade soil quality and a sink with
restorative land use and judicious management practices which create positive C and
nutrient budgets and conserve soil and water while improving soil structure and tilth.
(6) Soils are nonrenewable over a human time frame scales, but are renewable on a
geological scale. (7) Soil’s resilience to natural and anthropogenic perturbations
depends on its physical, chemical, and biological processes. Favorable chemical and
biological processes enhance resilience only under optimal soil physical properties
and processes, including structure, tilth, aeration, water retention and transmission,
and temperature. (8) The rate of restoration of the soil organic matter pool is extremely
slow, while that of its depletion is often very rapid. In general, restoration occurs on
a centennial time scale and depletion on a decadal time scale. (9) Soil structure
depends on stability and continuity of macro-, meso-, and micropores which are the
sites of physical, chemical, and biological processes that support soil’s life support
functions. Sustainable management systems enhance stability and continuity of
pores and voids over time and under diverse land uses. (10) Sustainable management
of agricultural ecosystems implies an increasing trend in net primary productivity per
unit input of off-farm resources along with improvement in soil quality and ancillary
ecosystem services such as increase in the ecosystem C pool, improvement in quality
and quantity of renewable fresh water resources, and increase in biodiversity.

Study Questions

1. Explain that soil is a limited natural resource. It is a renewable natural resource

in geological time frame, but it is a nonrenewable natural resource in human life
time frame.