Agriculture Reference
In-Depth Information
0
50
100
200
400 mg N kg
-1
Common urea
FIGURE 2.2
Root growth of upland rice at different N levels applied by common urea.
Coating urea with NBPT,
N
-(
n
-butyl-thiophosphoric triamide), 1.0 g kg
−10
reduced the cumula-
tive NH
3
loss by approximately 66% compared with uncoated urea, although the efficacy of this
compound was tied to the size and distribution of precipitation events following fertilization (Engel
et al., 2011). Mitigation of NH
3
volatilization from urea by NBPT has been attributed to a number
of factors, including a moderation of the soil pH rise that results with the production of ammonia
bicarbonate (Clay et al., 1990; Christianson et al., 1993) and reduction in the concentration of
NH
4
+
in the soil solution around the fertilizer placement microsite (Christianson et al., 1993), thereby
affecting the
NH
3
+
hydrolysis. The longevity of NBPT appeared to be greater in the calcareous soil
(pH 8.4) than in acidic soil (pH 5.5-6.5) (Engel et al., 2011).
Halvorson and Grosso (2012) reported that N fertilizer source affects the growing season soil
N
2
O emissions from irrigated corn system in Colorado. The use of controlled-release and stabilized
N sources reduced N
2
O emissions under no-till and strip-till corn production systems up to 66% as
compared to commonly used urea and up to 43% compared to urea ammonium nitrate. In addition,
urease and nitrification inhibitor additions to urea and urea ammonium nitrate resulted in significant
reductions in N
2
O emissions, as did polymer-coated urea. These authors concluded that the choice
of N source can be valid management alternatives for reducing N
2
O emissions to the environment
in semiarid areas. They compared the root growth of upland rice at different N rates applied by two
N sources (Figures 2.2 and 2.3). The root growth was more vigorous at an adequate N rate in both
0
50
100
200
400 mg N kg
-1
Polymer coated urea
FIGURE 2.3
Root growth of upland rice at different N levels applied by polymer-coated urea.
