Agriculture Reference
In-Depth Information
5
CU
4
3
PCU
2
CU (Y) = 2.45 + 0.02X - 0.000042X
2
PCU (Y) = 2.57 + 0.02X - 0.000061X
2
R
2
= 0.56**
R
2
= 0.76**
1
0
50
100
150 200
Nitrogen rate (mg kg
-1
)
250 00
350
FIGURE 3.36
Grain yield of upland rice as influenced by N rate and sources. The symbol CU means com-
mon urea and PCU means polymer-coated urea.
In another greenhouse experiment, the author studied the effects of two N sources (common
urea and polymer-coated urea) on the grain yield and panicle density of upland rice. The grain
yield of upland rice increased in a quadratic fashion by both sources when N was added in the
range of 0-400 mg kg
−1
(Figure 3.36). Maximum grain yield was obtained with the addition of
167 mg N kg
−1
by polymer-coated urea. Similarly, maximum grain yield was obtained with the
addition of 238 mg N kg
−1
by common urea. Fageria et al. (2011a) reported that maximum grain
yield of upland rice was obtained with the addition of 271 mg N kg
−1
by urea as a source of N
fertilizer. Grain yield was very similar by both sources of N. However, at the highest N rate, grain
yield was higher with the application of common urea compared to polymer-coated urea. But at
the lower rate of N (up to 200 mg N kg
−1
), it was inverse. The increase in grain yield of upland
rice with the addition of N was expected because Oxisols are deficient in N (Fageria and Baligar,
2005b; Fageria, 2013).
Panicle density was also increased in a quadratic fashion by both sources of N fertilization (Figure
3.37). Maximum panicle density was obtained with the addition of 233 mg N kg
−1
by polymer-coated
2.5
2.0
CU
1.5
PCU
1.0
CU (Y) = 0.95 + 0.01X - 0.00018X
2
R
2
= 0.81**
R
2
= 0.38**
PCU (Y) = 1.14 + 0.007X - 0.00015X
2
0.5
0
100 200 300
Nitrogen rate (mg kg
-1
)
400
FIGURE 3.37
Influence of two nitrogen sources on panicle number in upland rice. The symbol CU means
common urea and PCU means polymer-coated urea.
