Agriculture Reference
In-Depth Information
1st year
2nd year
90% of maximum
yield
90% of maximum
yield
7000
6000
5000
4000
Y= 3900.876 + 37.4993X - 0.11498X
2
R
2
= 0.9174**
3000
Y = 3400.874 + 33,8728X - 0.08110X
2
R
2
= 0.9649**
2000
1000
0
90% of maximum
y
i
e
l
d
90% of maximum
yield
6000
Average 3 years
5000
3rd year
4000
3000
Y= 3620.501 + 33.3055X - 0.09735X
2
R = 0.9686**
Y = 3560.268 + 28.5467X - 0.09599X
2
R
2
= 0.9181**
2000
1000
0
30
60
90
120
150
180
210
0
30
60
90
120
150
180
210
Nitrogen applied (kg N ha
-1
)
FIGURE 3.38
Response of lowland rice to nitrogen fertilization. (From Fageria, N. K. and V. C. Baligar.
2001.
Commun. Soil Sci. Plant Anal
. 32:1405-1429. With permission.)
the maximum grain yield (5731 kg ha
−1
) was obtained at 84 kg N ha
−1
. This means that there was
a residual effect of N application in lowland rice grown on an Inceptisol. The increase in grain
yield of lowland rice at an economical rate (120 kg N ha
−1
) in the first year was 76% as compared
to the control N treatment. Similarly, the increase in grain yield in the second and third years at
economical N rates (90 and 78 kg ha
−1
) was 69% and 41%, respectively. The average increase of
grain yield across the 3 years was 56% at the economical N rate of 84 kg ha
−1
. At the zero N level,
the grain yield was 3579, 3754, and 3702 kg ha
−1
in the first, second, and third years, respectively.
The average value of grain yield across the 3 years was 3678 kg ha
−1
at the zero N rate. This means
that rice grain yield under the control treatment (no N application) was quite good during 3 years of
experimentation. In the control N treatment, rice yields increased during the second and third years
of cultivation as compared to the first year of cultivation. Fageria and Baligar (1996) also reported
significant increases in grain yields of lowland rice grown on an Inceptisol in the central part of
Brazil. These authors reported that an average yield of 3 years (5523 kg ha
−1
) of lowland rice was
achieved with the application of 100 kg N ha
−1
and that grain yields at low fertility levels increased
with succeeding cropping years.
Increases in corn yield with the application of N are widely documented in different parts of the
world (Azeez et al., 2006; Riedell et al., 2009; Abbasi et al., 2012). The application of 250 kg N
ha
−1
has been reported as an optimum rate of N for corn in the semiarid environment of Pakistan
(Hammad et al., 2011). Torbert et al. (2001) reported that corn grain yields in Texas increased with
N fertilizer up to 168 kg N ha
−1
in a year with sufficient rainfall. Similarly, Ma and Subedi (2005)
observed that the yield of corn increased with up to 120 kg N ha
−1
in Ontario, Canada. Abbasi et al.
