Agriculture Reference
In-Depth Information
efficiency results reported in the literature varied from crop species to crop species and genotypes
within species (Fageria et al., 2003). It was also influenced by crop management practices. Raun
and Johnson (1999) reported that, worldwide, the ARE efficiency of N for cereal production (wheat,
corn, rice, barley, sorghum, oat, millet, and rye) is approximately 33%. These authors also reported
that the unaccounted 67% N loss represents a US$15.9 billion annual loss of N fertilizer. Plant N
losses have accounted for 52-73% of the unaccounted N using
15
N in corn research (Francis et al.,
1997), and between 21% (Harper et al., 1997) and 41% (Diagger et al., 1976) in winter wheat. Gases
plant N loss excess of 45 kg N ha
−1
year
−1
has also been documented in soybean (Stutte et al., 1979).
Bliss (1993) reported that in carefully conducted grain legume experiments, rarely is more than
30-50% of the applied N recovered in the plant.
Giambalvo et al. (2010) reported that the N recovery efficiency of wheat varied from 29.9% in
the first year to 10.4% in the second year. These authors reported that the decrease observed in the
second year may be due to the different characteristics of the soils in which the experiments were
conducted. These authors also reported that their values of N recovery for wheat were comparable
to values obtained in Tunisia by Sanaa et al. (1992), and in Syria by Pilbeam et al. (1997). Lopez-
Bellido et al. (2006), in a study performed in Spain on durum wheat, reported values of labeled
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N fertilizer recovery ranging from 12.7% when applied at sowing to 41.6% when applied at top
dressing.
Fageria and Baligar (2001) reported that N recovery efficiency in irrigated or flooded rice is
about 40%. De Datta and Buresh (1989) reported that Asia uses about 40% of the world's N fertil-
izer and about 60% of this is used for lowland rice production. According to De Datta and Buresh
(1989), N recovery efficiency in lowland rice in Asia is around 40%. Similarly, Fageria et al.
(2007) reported that N recovery efficiency use efficiency varied from 23% to 37% in irrigated or
flooded rice among five flooded rice genotypes, with an average value of 29%. Apparent fertil-
izer N recovery efficiency in wheat was reported to be in the range of 21-59% depending on the
year of cultivation, N rate, and soil preparation methods (Dalal et al., 2011). Ladha et al. (2005)
reported that the global NUE for wheat is 34%. Similarly, Randall et al. (2003) reported that the
global NUE for corn is about 31%. All these results suggest that a large part of applied N is lost
in the soil-plant system.
Loss has been through ammonia volatilization, although leaching and denitrification also con-
tribute to inefficient utilization. These authors further reported that because of the nature of these
processes, attempts to reduce losses and improving recover efficiency have focused on water man-
agement. In the case of ammonia volatilization, loss is closely related to the concentration of
ammonia in the floodwater. The estimates of the total losses of N as ammonia are between 36%
and 44% (Fillery and De Datta, 1989). This loss was reduced to 22% by the use of urease inhibitors
(Fillery and De Datta, 1989), but the cost is prohibitive (Buresh et al., 1988). Two approaches
to reducing loss by reducing floodwater concentration of ammonia have been: (i) to drain the
floodwater and apply the fertilizer to the soil surface; and (ii) to place the fertilizer below the soil
surface. It was confirmed that losses were less when the fertilizer was applied to the drained soil
surface than when it was broadcast on the floodwater (De Datta et al., 1987). It was shown that
UE could be raised to more than 60% by placing the fertilizer below the surface of the soil (deep
placement) (De Datta et al., 1989).
Nitrogen recovery efficiency as determined by the
15
N tracer technique in tropical lowland rice
production has been reported to be approximately 30-50% (Bronsonet al., 2000; Eagle et al., 2001).
Wilson et al. (1989) reported that, dependent on the application time, the rice plant had an observed
total recovery of 53-74% of the applied N. Guindo et al. (1992) reported that N recovery effi-
ciency of
15
N values, for drill-seeded, delayed flood rice in the range of 72-79% when
15
N fertilizer
was applied a day before flood establishment and into the flood water at panicle differentiation.
Dillon et al. (2012) reported that N recovery efficiency in flooded rice varied from 43% to 71% for
multiple sources and multiple times between N fertilizer application and flooding across multiple
environments.
