Agriculture Reference
In-Depth Information
an assessment of northern Great Plains grassland systems, the pastures evaluated
were significant sinks for SOC and minor sinks for methane. Fertilization of intro-
duced perennial pasture resulted in soil nitrous oxide emissions that were three times
greater than unfertilized native pasture with high and medium stocking rates. Liebig
et al. (2010) attributed differences in enteric methane emissions from the pastures
in their study to differences in stocking rate, although forage and feed quality is a
significant factor in enteric methane emission rates from ruminant livestock.
Eswaran et al. (1997b) reported on the development of the Food and Agriculture
Organization (FAO) Soil Map of the World, which, together with other data, can be
used to make continent-level assessments of land productivity and sustainability.
Africa, with a total land mass of about 307 million ha and a population exceeding 746
million, has generally lagged in agricultural development compared with other conti-
nents (Eswaran et al. 1997b). Fifty-five percent of the land in Africa is unsuitable for
any kind of agriculture except nomadic grazing. These lands, which are largely des-
erts and steep to very steep lands, have constraints to sustainability; however, about
30% of the population depends on these fragile land resources (Eswaran et al. 1997a).
These authors suggested the need for major investments to enhance the productivity
of the soil resources available to resource-poor farmers of the African continent.
Abberton et al. (2008) reviewed the potential for genetic improvement of forage
species to reduce the environmental footprint of grazing systems through improved
nutrient use efficiency of plants by reducing fertilizer requirements and improving
forage quality. Such changes would improve livestock nutrient use efficiency and
reduce methane emissions from ruminant grazers.
4.1.2 S
mallholder
G
razInG
S
yStemS
The term “smallholder” is relative to the size of landholding that prevails in a par-
ticular country or region; however, the land area available to a smallholder house-
hold is substantially less than to the regional average. Often, smallholders depend on
multiple sources of income, of which agricultural production is only one. Although
smallholder households produce a relatively lower portion of marketed agricultural
products than larger agricultural operations, the land management by smallholder
households can constitute a large portion of the landscape of a region or country.
In addition, food and goods are often consumed and utilized within the household
where they are produced and not typically accounted for in national production indi-
ces. Therefore, smallholder production may be undervalued in national and global
assessments. In lower-income countries, land, capital, credit, and other resources
available to smallholder households are limited. These households must cope with
a variety of risks and vulnerabilities (FAO 2013), and livestock provide options for
coping with environmental stresses, owing to their mobility, ability to survive on a
wide variety of feedstuffs, and provision of food for household consumption or local
marketing. In middle- or higher-income countries, the family heritage on a particular
piece of land or the rural lifestyle may be equally, or more important than income
from smallholder agriculture.
Sere and Steinfeld (1996) classified ruminate production systems on the basis of
solely livestock versus mixed crop-livestock systems (Figure 4.3). In this chapter,
