Human Dimensions That Drive Soil Degradation - Principles of Sustainable Soil Management in Agroecosystems - page 172

the question, “What factors promote the adoption and diffusion of innovations
throughout a community?” Soil conservation practices and projects have long been
studied in this field (see Prokopy et al. 2008 for a comprehensive review). While
BMPs differ by local context, some common examples include grass waterways,
control drainage, reduced-till and no-till practices, vegetated buffers along streams,
phosphate-free fertilizers, manure management and nutrient management plan-
ning, and fencing animals out of streams.
7.3.2 I ntensIfIcatIon of a grIcuLturaL m anagement
Intensification of agricultural management refers to increased inputs (e.g., labor, pes-
ticides, herbicides, fertilizer, water, mechanized equipment) in an effort to increase
agricultural yield per unit area. This often involves greater use of technology. From
1961 to 1996, intensification permitted a doubling of the world's food production
with only a 10% increase in arable land (Tilman 1999).
While intensification may increase soil fertility in the short run, many researchers
have identified numerous ways that intensification causes soil degradation. The intro-
duction of machinery compacts soil, reducing its capacity to absorb rainwater, thus
speeding up runoff and resulting in erosion. This is also known as “mining” of the soil's
organic matter and nutrients because they are removed rather than renewed with use
(Gudger and Barker 1993). The negative effects of intensive agricultural practices on the
sequestration of soil carbon are well documented (Burke et al. 1989; Paul et al. 1997).
Furthermore, the “green revolution” model of intensive agriculture is highly
water intensive and requires increased use of chemical fertilizers and pesticides. The
increased irrigation necessary for high-yield plant varieties causes soil salinization
and waterlogging (Rosegrant et al. 2009; Urama 2005; Howes 2008). Waterlogging
is caused by irrigation water seeping through the soil and raising the water table.
Salinization occurs when the highly mineralized groundwater rises. If it reaches the
zone where plant roots are growing, it dehydrates the plants. The dehydrated plants
then wilt and finally die. The FAO (1996) declared that there was 20 to 30 million ha
of land severely degraded by salinization and an additional 60 to 80 million ha that
was affected to some extent by saturation and salinization.
Additionally, the application of chemical fertilizers can cause excesses of soil nitro-
gen, which can ultimately harm the cultivation potential of the soil (Matson et al. 1997;
Turner and Ali 1996). Application of inorganic nitrogen, which has greater environ-
mental effects than most other inputs (Vogt et al. 2010), has grown to about seven times
what it was in the 1960s and is still growing. Besides nitrogen's well-known effects
on surface and groundwater, it also has a detrimental effect on soil bacteria. Although
beneficial at optimal application levels, this is often exceeded and overapplication
increases the above-mentioned harmful effects (Spiertz 2010; Guo et al. 2011), decreas-
ing yield and the effectiveness of manufactured fertilizers (Marenya and Barrett 2009).
Although pesticides have greatly increased agricultural production, their indis-
criminate use can be harmful. The greatest concerns over pesticides revolve around
their adverse effects to humans and the environment (Gaby 2004; Weiss et al. 2004),
but they also can decrease soil quality by reducing beneficial insect populations
(Gudger and Barker 1993). Pesticides have been known to accumulate in soil and be