Agriculture Reference
In-Depth Information
TABLE 9.2
Yields of Continuous Winter Wheat, Sugar Beet, and Maize and Crops
Grown in Rotation (1994-2011)
Yield Increase in Crop
Rotation Relative to
Continuous Cultures,
Mg/ha and %
Increase with
Fertilizer
Fertilizer Use
Cropping
Systems
Unfertilized
Fertilized
Mg/ha
%
LSD
05
Unfertilized
Fertilized
Winter Wheat
Continuous
crop
1.95
2.80
0.85
43.6
—
—
Crop rotation
4.73
5.10
0.37
7.8
0.20
2.78 (142.6)
2.30 (82.1)
Sugar Beet
Continuous
crop
8.54
16.83
8.29
97.1
—
—
Crop rotation
32.55
42.65
10.1
31.0
2.1
24.01 (281.1)
25.82 (153.4)
Maize Grain Yield
Continuous
crop
3.81
5.47
1.66
43.6
—
—
Crop rotation
5.43
5.85
0.42
7.7
0.27
1.62 (42.5)
0.38 (6.9)
individual crops differ (Table 9.2) but the yield increase that can be attributed to fer-
tilizers is higher with continuous monocultures. Furthermore, agronomic yield under
crop rotation relative to continuous monoculture is significantly more than through
the benefits of fertilization, except for the grain yield of maize.
Despite the apparent increase in yield, fertilizer use decreased the positive effects
of crop rotation. Probably, the visible effects of fertilizers masked the benefits of
crop rotation. In the beginning of industrial intensification, fertilizers and the use
of agrochemicals to control weeds, pests, and diseases appeared to compensate for
the simplification of crop rotations during the period of extraordinary specialization
and concentration of agricultural production. Low prices for nonrenewable sources
of energy and their derivates (mineral fertilizers and agrochemicals) made the new
approach attractive. However, in reality, fertilizers are no substitute for crop rotation.
Alas, cheap fuel, and fertilizers are now a history.
9.3.2 H
igH
-Y
ielding
v
arieties
and
H
Ybrids
The other misconception has been the perception that agronomic yields can simply
be increased by introducing new varieties of field crops along with higher rates of
fertilizer. However, experimental data for winter wheat in the Selectia long-term
experiments do not support this perception (Table 9.3).
