Agriculture Reference
In-Depth Information
6000
5000
4000
3000
2000
Y = 2493.01 + 36.21X - 0.14X
2
R
2
= 0.52*
1000
0
50
100
150
200
Nitrogen rate (kg ha
-1
)
FIGURE 8.18
Response of upland rice to N fertilization.
fertilization grown on a Brazilian Oxisol (Figure 8.18). The response was significant and quadratic.
A maximum grain yield of about 5000 kg ha
−1
was obtained with the addition of 129 kg N ha
−1
applied twice times. Half of the N was applied at sowing and the remaining half at 45 days after
sowing corresponding to the active tillering growth stage.
The author also studied an adequate N rate for 12 lowland rice genotypes in a field experiment
for two consecutive years (Table 8.7). The yield of 12 genotypes increased significantly in a qua-
dratic fashion with the addition of the N fertilizer from 0 to 200 kg ha
−1
. A maximum grain yield
TABLE 8.7
Relationship between Nitrogen Rate (X) and Grain Yield (Y) of 12
Lowland Rice Genotypes
Genotype
Regression Equation
R
2
NRMY
BRS Tropical
Y = 4149.51 + 42.34X − 0.126X
2
0.62**
168
BRS Jaçanã
Y = 3500.10 + 39.75X − 0.152X
2
0.54**
131
BRA 02654
Y = 3596.41 + 32.46X − 0.126X
2
0.57**
129
BRA 051077
Y = 3367.42 + 32.59X − 0.134X
2
0.58**
122
BRA 051083
Y = 4142.04 + 25.47X − 0.059X
2
0.79**
215
BRA 051108
Y = 3375.72 + 28.58X − 0.083X
2
0.78**
172
BRA 051126
Y = 3961.13 + 36.66X − 0.106X
2
0.82**
173
BRA 051129
Y = 3598.17 + 37.82X − 0.138X
2
0.58**
137
BRA 051130
Y = 3991.41 + 42.91X − 0.143X
2
0.86**
150
BRA 051134
Y = 3843.46 + 35.04X − 0.103X
2
0.75**
170
BRA 051135
Y = 3566.95 + 32.53X − 0.092X
2
0.88**
177
BRA 051250
0.75**
135
Y = 3306.92 + 40.79X − 0.151X
2
Note:
NRMY = nitrogen rate for maximum grain yield calculated by quadratic regression equa-
tions. Values are averages of 2 years' data.
**Significant at the 1% probability level.
