Agriculture Reference
In-Depth Information
5.2.4 a
pparent
r
eCoverY
e
ffICIenCY
Fertilizer N recovery efficiency also known as ARE is an important index to measure the fertil-
izer economic and environmental benefits (Xiong et al., 2013). It can be estimated by the ratio of
increased plant N uptake that results from N application to the amount of applied N (Tian et al.,
2011). ARE is defined as the quantity of N uptake per unit of N applied (Fageria et al., 2010). It can
be calculated by using the following equation:
NN
quantity of N applied
−
f
u
ARE
(%) =
×
100
where N
f
is the N accumulation by total biological yield (straw plus grain) in the fertilized plot (kg),
N
u
is the N accumulation by the total biological yield (straw plus grain) in the unfertilized plot (kg),
and the quantity of N applied also in kg. This is related to field experimental data. If it is a green-
house experiment, N uptake values can be expressed in mg and quantity of N applied should also
be expressed in mg.
Nitrogen fertilizer has played an important role in increasing crop yields worldwide and the total
consumption of N has increased gradually (Zhu and Chen, 2002; Singh et al., 2012; Yang et al.,
2012) However, fertilizer NUE is low in most agroecological regions. For example, in rice, the N
recovery efficiency is reported to be in the range of 25-45% and average about 35% (Dobermann
and Cassman, 2002). More than half of the N fertilizer applied is lost and results not only in an envi-
ronmental hazard but also in a substantial economic loss (Matsonet et al., 1997; Galloway, 1998;
Choudhury and Kennedy, 2005; Li et al., 2009). Even though practices such as deep application
(Roberts et al., 2009) and subsequent multiple topdressings of N fertilizer improve N fertilizer use
efficiency, lack of application machinery and the rising cost of labor and the shortage of agricultural
workers often limit the implementation of these practices (Zhang, 2008).
Fertilizer nutrients are not utilized efficiently in agriculture and the apparent recovery of fertil-
izer N in the soil-plant system seldom exceeds 50% of the N applied while the remaining is lost
(Abbasi et al., 2005). Rice ARE in China ranged from 18% to 66% (Wang et al., 2001; Peng et al.,
2006). Fageria and Baligar (2001) determined the ARE of lowland rice under different N rates
(Table 5.5). It varied from 32% to 50%, with an average value of 39%. It was also significantly influ-
enced by N levels and the variation was 82% due to the application of N rates. Nitrogen recovery
TABLE 5.5
Apparent Recovery Efficiency of Lowland Rice under Different N Levels
Nitrogen Rate (kg ha
−1
)
Apparent Recovery Efficiency (%)
30
49
60
50
90
37
120
38
150
34
180
33
210
32
Average
39
0.82
**
R
2
Source:
Adapted from Fageria, N. K. and V. C. Baligar. 2001.
Commun. Soil Sci. Plant Anal
.
32:1405-1429.
**Significant at the 5% probability level.
