Agriculture Reference
In-Depth Information
TABLE 3.16
Relationship between the Nitrogen Rate and Plant Height, Straw Yield,
Grain Yield, and Panicle Density of Lowland Rice
Variable
a
Regression Equation
R
2
N versus PH (AS)
0.71**
Y = 84.04 + 0.1220X - 0.00015X
2
N versus PH (UC)
0.84**
Y = 84.12 + 0.0931X - 0.000069X
2
N versus pH (UP)
Y = 83.73 + 0.1441X - 0.00031X
2
0.74**
N versus SY (AS)
Y = 6.51 + 0.0365X
0.95**
N versus SY (UC)
Y = 5.95 + 0.0549X - 0.000049X
2
0.93**
N versus SY (UP)
Y = 6.69 + 0.0488X
0.98**
N versus GY (AS)
Y = 1.73 + 0.0301X
0.96**
N versus GY (UC)
Y = 1.05 + 0.0385X - 0.000056X
2
0.85**
N versus GY (UP)
Y = 0.64 + 0.0565X - 0.00014X
2
0.78**
N versus PD (AS)
Y = 2.50 + 0.0186X - 0.000031X
2
0.55**
N versus PD (UC)
Y = 2.22 + 0.0166X - 0.000034X
2
0.66**
N versus PD (UP)
Y = 2.16 + 0.0219X - 0.000060X
2
0.78**
N versus RDW (AS)
Y = 1.39 + 0.0134X - 0.000024X
2
0.46*
N versus RDW (UC)
Y = 1.66 + 0.0038X
0.51**
N versus RDW (UP)
Y = 1.52 + 0.0083X
0.70**
a
PH = plant height, SY = straw yield, GY = grain yield, and PD = panicle density. AS = ammo-
nium sulfate, UC = urea common, and UP = urea polymer coated.
*,**Significant at the 5% and 1% probability levels, respectively.
reported by Fageria and Barbosa Filho (2001) and Fageria et al. (2011a) in lowland rice grown on
Brazilian Inceptisol.
Plant height varied from 83.75 to 110.50 cm, with an average value of 98.02 cm. At 100 and
200 mg N kg
−1
, maximum plant height was produced by ammonium sulfate and polymer-coated
urea and minimum plant height was produced by common urea. At 400 mg N kg
−1
, maximum
plant height was produced by common urea, followed by ammonium sulfate and polymer-coated
urea. A significant variation in plant height due to N sources has been reported by Fageria et al.
(2011). Plant height is an important trait in determining plant lodging and response to N fertilization
(Fageria, 2007a). It is also an important trait due to the positive significant relationship with grain
yield (Y = −61.36 + 1.07X-0.0040X
2
, R
2
= 0.47*). A positive significant relationship between plant
height and grain yield of lowland rice has been reported by Fageria and Baligar (2001), Fageria
(2007a), and Fageria (2001b). Plant height is genetically controlled and also influenced by environ-
mental factors such as essential plant nutrients at an adequate level (Fageria, 2007a). During the
1960s, rice breeders made excellent progress in the development of dwarf cultivars that responded
to heavy application of N (Jennings et al., 1979).
Straw yield increased significantly with the addition of N fertilizer by three N sources. The
response of plant height to N fertilizer was linear for ammonium sulfate and polymer-coated urea
and quadratic with the addition of N in the form of common urea (Table 3.16). The variation in
straw yield was 95% with the addition of N in the form of ammonium sulfate, 93% in the form of
common urea, and 98% when N was added as polymer-coated urea. Maximum straw yield was
obtained with the addition of 400 mg N kg
−1
compared to the lower N rate at three N sources.
Among the N sources, maximum straw yield was produced by polymer-coated urea, followed by
the remaining two sources. Improvement in straw yield with the addition of N has been reported by
Fageria and Baligar (2001), Fageria et al. (2009), and Fageria et al. (2011a). Straw yield was having
