Managing Soil Carbon for Multiple Benefits – Positive Exemplars: North America - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 287

24 Managing Soil Carbon for Multiple
Benefits - Positive Exemplars:
North America

Rich Conant*

Abstract
Implementing land-use practices that maximize the soil carbon (C) stocks can simultaneously lead to
additional economic and social benefits while maintaining or enhancing the ecological support func-
tions of the land resources. This enhances the ability to meet our near-term needs while ensuring the
ability of future generations to meet theirs. Within North America, numerous opportunities exist to
increase soil fertility, enhance soil water balance, increase production efficiency and reduce reliance
on external inputs, which will enhance the resilience of production and yields in the face of climate
variability. Practices that build resilience in the face of current climate variability are also expected to
ameliorate some of the effects of the forecast increase in future extreme events; thus, building C stocks
can foster adaptation to a changing climate. This chapter reviews North American agricultural and
grazing land management practices that can sequester C in soils, their potential to mitigation green-
house gas emissions and the additional benefits that arise from these practices.

Introduction

a small, transient carbon pool (compared to
forests) and hence soils constitute the dom-
inant carbon stock. Cropland systems can be
among the most productive ecosystems, but
in some cases restricted growing season
length, fallow periods and grazing-induced
shifts in species composition or production
can reduce carbon uptake relative to that in
other ecosystems. These factors, along with
tillage-induced soil disturbances and the re-
moval of plant carbon through harvest, have
depleted soil carbon stocks by 20- 40% or
more in relation to pre-cultivated conditions
(Davidson and Ackerman, 1993; Houghton
and Goodale, 2004). Soil organic carbon (SOC)
stocks in grazing lands in North America

The main processes governing the carbon
(C) balance of agricultural and grazing
lands are the same as for other ecosystems:
the photosynthetic uptake and assimilation
of CO 2 into organic compounds and the re-
lease of gaseous carbon through respiration
(primarily CO 2 but also CH 4 ) and fire. In
agricultural lands, carbon assimilation is
directed towards the production of food,
fibre and forage by manipulating species
composition and growing conditions (soil
fertility, irrigation, etc.). Biomass in agri-
cultural and grassland systems (being pre-
dominantly herbaceous, i.e. non-woody), is