Marginality Principle - Principles of Sustainable Soil Management in Agroecosystems - page 35

concluded that the need to reduce erosion was paramount to avoiding declining
productivity in soils.
2.6 MULTIFUNCTIONALITY: OPTIMUM
PERFORMANCE OF SOIL RESOURCE
Marginal soils have marginal performance as evidenced by our examination of crop
productivity, water availability, and environmental quality. However, there are other
dimensions to this problem that need to be considered because of the role soils have
in the ecosystem in providing a foundation for optimal primary productivity. Hatfield
(2006) has shown that the multifunctionality of agricultural systems is dependent on
a high-quality soil resource to optimize ecosystem services. A similar statement can
be made about the role of soil in providing resilience to climate change. This aspect
has not been fully investigated and needs additional research; however, adequate soil
water is critical for optimum plant growth and stress avoidance. This can come only
as a result of ensuring that soil water storage is maximized through the addition of
SOC content.
2.6.1 S oil m anagement to r eDuce m arginality
Conservation practices encompass a range of different systems employed to reduce
the off-site impacts of agricultural systems and to ultimately enhance the natural
resources. Delgado et al. (2011) recently reviewed the state of different practices
capable of mitigating and adapting to climate change. They listed several exam-
ples of potential mitigation strategies including the following: “increasing soil C
sequestration to improve soil function; reducing CH 4 emissions from ruminants;
using slow release fertilizers, increasing N-use efficiencies for cropping systems;
capturing nutrients and energy from manure, crop residues, and cover crop manage-
ment; and using more efficient power sources and renewable energy.” Specifically
for soil and water practices, they identified a range of practices dealing with erosion,
irrigation infrastructure, more diverse cropping systems, crop varieties more toler-
ant to drought and heat stress, synchronizing planting and harvesting with shifts in
the hydrologic cycle, managing soil and crops to increase WUE, evaluating agri-
cultural commodities for their water footprint and environmental traits, increasing
soil C sequestration, increasing N-use efficiency, and implementing precision and
targeted conservation practices to increase the effectiveness of practices to handle
the increased temporal and spatial variation. These practices represent a range of
potential ideas and concepts that, if implemented, would have a positive impact on
the resilience of the production system to climate stresses and a positive feedback in
terms of contributing to climate change mitigation.
In this process, it is critical to understand the feedback that occurs among all of
the components in an agricultural system and their linkages. As an example, ET
will increase with warming temperatures and cause crop water use rates to increase,
leading to a faster depletion of the soil water reserves. In soils with limited soil water
holding capacity, this will create variation in total crop water use and, ultimately,