Agriculture Reference
In-Depth Information
a considerable amount of urea to be accommodated and released (Kim et al., 2011). Furthermore,
their high capacity for water retention and cation adsorption could play an excellent role in suppress-
ing NH
3
emission by exchanging
NH
4
+
ions (Kim et al., 2011). Several studies have reported that
urea intercalated in montmorillonite leads to a considerable improvement of N use efficiency in soils
(Park et al., 2004; Kim et al., 2010, 2011).
2.9.10 a
doptInG
C
rop
-l
IvestoCk
I
nteGratIon
In
C
roppInG
s
Ystem
Agricultural production systems have trended toward high-input, highly specialized monoculture
and simple rotation systems. While these systems have greatly increased productivity, the stress on
ecosystems and natural resources has also increased. Adopting crop-livestock integration (CLIS) is
an important strategy in reducing N losses from soil-plant system. Crop and livestock activities can
compromise the sustainability of an agricultural system (Crusciol et al., 2013). These two activities
in isolation can reduce soil fertility, increase soil erosion, decrease soil organic matter and crop
yield, and increase the risk of pasture degradation (Crusciol et al., 2010). However, adopting CLIS
can decrease the negative effects, being a mixed system of land use characterized by diversification,
crop rotation, intercropping systems (cash crop with forage species), and crops and livestock in the
same area (Tracy and Zhang, 2008; Crusciol et al., 2013).
Russelle et al. (2007) reviewed numerous studies regarding integrated crop-livestock systems
and concluded that the systems may provide economic (Small and McCaughey, 1999) and environ-
mental benefits (Drinkwater et al., 1998). An integrated crop-livestock system has been shown to
reduce irrigation demand as compared to a monoculture cotton production system in the Texas High
Plains (Allen et al., 2005, 2012; Johnson et al., 2013). Johnson et al. (2013) also reported that the
integrated system could be a viable alternative in an area of the region where irrigation is limited
due to aquifer depletion and/or pumping regulation. The integrated system had less economic risk
associated with the variation in profitability and added ecological diversity that benefited soil health
and wildlife populations (Johnson et al., 2013).
In recent years, Brazil has been increasingly using CLIS, which includes, as one of its modalities,
the intercropping of grain crops such as corn, soybean, rice, sorghum, and dry bean with peren-
nial tropical forage (mainly palisadegrass—
Brachiaria brizantha
Hochst. Ex A. Rich Stapf) in
no-tillage system (Crusciol et al., 2013). This intercropping is an outstanding alternative for forage
production during the dry season and provides residue for the no-till system in the next crop season
(Crusciol et al., 2010).
Palisadegrass is a perennial forage species originating in Africa, and is well adapted to Brazilian
climates. It has a deep root system and can tolerate drought and can produce dry biomass up to 20 Mg
ha
−1
a year (Crusciol et al., 2010). Its addition in the CLIS system can provide adequate residue on the
soil surface throughout the year, improves dynamic cycling of nutrients as well as physical charac-
teristics of the soil, and, therefore, proper nutrition and yield of the following crop (Baributsa et al.,
2008; Crusciol et al., 2013). Crusciol et al. (2013) reported that the adoption of CLIS in a no-tillage
system has been one of the best alternatives in guiding tropical agricultural systems toward sustain-
ability and can result in diversity of production, higher economic returns, and improve crop growing
conditions, with emphasis on nutrient cycling and soil quality. Pacheco et al. (2011) reported that pali-
sadegrass growing in the dry season had 142 kg ha
−1
N, 14 kg ha
−1
P, 127 kg ha
−1
K, 91 kg ha
−1
Ca, and
59 kg ha
−1
Mg in its tops at the beginning of the subsequent wet season. Crusciol et al. (2010) reported
that, after two growing seasons, the soil organic matter in the top 0-5 cm soil layer was 2.5 g m
−3
in
a corn and palisadegrass intercropping system and 2.2 g m
−3
for corn alone, differing significantly.
2.9.11 a
doptInG
o
rGanIC
f
armInG
Several authors have examined the issue of nitrate leaching from arable land or farming systems
and concluded that agriculture activities are one of the main sources of NO
3
leaching to aquifers
