Agriculture Reference
In-Depth Information
5.2.5 u
tIlIzatIon
e
ffICIenCY
UE is defined as the product of physiological and apparent recovery efficiency. It can be calculated
by using the following equation:
UE (kg kg
−1
) = PE × ARE
Fageria and Baligar (2001) studied the UE of N in lowland rice under different N levels (Table
5.7). It varied from 36 to 83 kg kg
−1
, with an average value of 58 kg kg
−1
. It decreased with increas-
ing N rates and was significantly influenced by N levels. The variation in the UE was 90% due to
the addition of N in the range of 30-210 kg ha
−1
. Fageria et al. (2010) studied the UE and other NUE
in upland rice under greenhouse conditions (Table 5.8).
AE and UE were significantly different among genotypes. PE, APE, and ARE were also varied
among genotypes; however, the difference was statistically not significant. The AE varied from 12.8
to 26.7 mg grain produced per mg N applied with an average value of 21.4 mg grain produced per
mg of N applied. The average value across the genotypes of PE was 86.6 mg dry matter produc-
tion (grain plus straw) per mg N accumulated in grain and straw. The average value of APE was
45.2 mg grain produced per mg N accumulated in grain and straw. Fageria and Barbosa Filho (2001)
determined the APE in eight lowland rice genotypes and reported an average value of 45.5 mg grain
produced per mg N accumulated in the grain and straw. Hence, the APE of lowland and upland rice
is comparable. The average ARE was 49.2%. The ARE in lowland rice is reported to be in the range
of 31-40% in major rice-growing regions of the world (Cassman et al., 2002). Fageria and Baligar
(2001) reported that the average ARE in lowland rice in Brazilian Inceptisol was 39%. This means
that the ARE in upland rice is higher compared to lowland rice. The highest grain yield producing
genotype CNAs 8993 had the highest AE, whereas the lowest yielding genotype CNA 8170 was
having lowest AE. The genotype CNAs 8992 was also having highest PE and APE and reasonably
good values of ARE and EU.
The author studied NUE in dry bean genotypes (Table 5.9). AE, PE, APE, ARE, and UE of
N were significantly influenced by genotype treatment (Table 5.9). However, genotype means by
Tukey's test were separated only for PE and APE. Further, the variation in NUEs among bean
genotypes was reported to be related to genetic variability in N uptake and utilization under tropical
conditions (Lynch and White, 1992; Lynch and Rodriguez, 1994).
TABLE 5.7
Utilization Efficiency of Lowland Rice under Different N Levels
Nitrogen Rate (kg ha
−1
)
Utilization Efficiency (kg kg
−
1
)
30
76
60
83
90
67
120
50
150
50
180
42
210
36
Average
58
0.90
**
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.
