Agriculture Reference
In-Depth Information
the sources as compared to the control treatment. Vigorous root system may absorb more water and
nutrients, including N and, consequently, the chances are less loss of N from the rhizosphere.
Compared with common urea, polymer-coated urea has been reported to increase apparent N
use efficiency in cabbage (
Brassica oleracea
var.
capitata,
Wiedenfeld, 1986), corn (
Zea mays
L.,
Noellsch et al., 2009), potato (
Solanaum tuberosum
L., Wilson et al., 2009), and barley (
Hordeum
vulgare
L., Shoji et al., 2001). Xu et al. (2013) reported that 15-33% of applied N was volatilized
as NH
3
under common urea from paddy soils, which was similar to those observed in other studies
(Roelcke et al., 2002; Hayashi et al., 2008;). In contrast, only 3-15% of applied N from polymer-
coated urea was lost through NH
3
volatilization (Xu et al., 2013). These results are similar to those
observed in other studies that showed the application of polymer-coated urea reduced N loss and
increased N use efficiency (Chen et al., 2008; Patil et al., 2010; Soon et al., 2011). Polymer-coated
urea has been reported to minimize N loss in poorly drained, low-lying areas (Noellsch et al., 2009)
and in sandy soils during high rainfall-growing seasons (Zvomuya et al., 2003). Surface applica-
tions of polymer-coated urea have also been found to reduce ammonia volatilization loss by 60% as
compared to noncoated urea (Rochette et al., 2009a,b).
2.9.4 a
doptInG
a
pproprIate
C
roppInG
s
Ystem
Adopting the appropriate cropping system is an important strategy in the reduction of gaseous emis-
sion by N sources used in crop production (Lemke et al., 1999; Drury et al., 2006; Mosier et al.,
2006; Sainju et al., 2012a). The cropping system can affect the quality and quantity of crop residue
returned to the soil and can influence the CO
2
and N
2
O emissions (Mosier et al., 2006; Dusenbury
et al., 2008; Robertson and Vitousek, 2009). The use of the organic farming system is one of the
very attractive strategies in improving soil quality and reducing N losses (Teasdale et al., 2007;
Lynch et al., 2011). Sainju (2013) studied the effects of tillage, cropping sequence, and the N fertil-
ization rate on N contents in dryland crop biomass, surface residue, and soil at the 0-120 cm depth
and also estimated N balance. No-till continuous cropping increased biomass and surface residue
of N, but conventional-till crop fallow increased soil available N. Because of increased soil N stor-
age and reduced N requirement to malt barley, NTB-P (no-till malt barley-pea) with 40 kg N ha
−1
may reduce N loss due to leaching, volatilization, and denitrification compared to other treatments.
Aase and Pikul (1995), Jones and Popham (1997), and Sainju (2013) reported that the traditional
farming system using conventional tillage with crop fallow can conserve soil water during fallow,
increase N availability due to increased mineralization, control weeds, sustain crop yields, and
reduce the risk of crop failure. The system, however, can reduce soil N storage because of increased
erosion and mineralization of organic N and reduced plant residue N returned to the soil due to the
absence of crops during fallow (Bowman et al., 1999; Halvorson et al., 2002). Enhanced microbial
activity due to increased soil temperature and water content during fallow can further reduce N
storage (Halvorson et al., 2002). Studies have shown that tillage with crop fallow has reduced soil
N storage by 30-50% in the last 50-100 years (Peterson et al., 1998) and reduced annualized crop
yields (Aase and Pikul, 1995; Sainju 2013). As a result, the system became unsustainable and uneco-
nomical (Aase and Schaefer, 1996; Dhuyvetter et al., 1996).
2.9.5 u
se
of
C
onservatIon
t
IllaGe
Conventional tillage increases nitrification process and hence increases
NO
3
−
leaching. There are
reports in the literature that
NO
3
−
leaching is lower in the conservation tillage as compared to con-
ventional tillage (Meek et al., 1995). Evans et al. (1996) have reported that greater accumulation of
NO
3
−
under a grain legume such as peas compared to a cereal, such as barley, indicates greater gen-
eration of H
+
ions. The greater
NO
3
−
concentrations are likely to accelerate
NO
3
−
leaching, leaving
soil acid nonneutralized (Bolan and Hedley, 2003). McKenney et al. (1995) have reported that the
addition of residues with high C/N ratio increases the immobilization of N and thereby decreases
