Agriculture Reference
In-Depth Information
TABLE 9.3
Yield Increase of Winter Wheat under the Influence of
New, High-Yielding Varieties Grown in Crop Rotation
and as Continuous Wheat, Average for 1994-2011
Unfertilized
Fertilized
Crop Rotation,
Continuous Wheat
Mg/ha
%
Mg/ha
%
LSD 05
Crop rotation
0.53
12.6
0.56
12.3
0.20
Continuous wheat
0.13
7.1
0.06
2.2
Any additional yield from new varieties was similar in fertilized and unfertil-
ized plots. Thus, the additional yield is produced from inherent soil fertility because
new varieties require additional plant nutrients compared with traditional varieties.
Moreover, the yield increase from new varieties (12.3%-12.6%) is significantly lower
than the beneficial influence of crop rotation, and such an increase was achieved only
in crop rotation. The yield increase from new varieties under continuous wheat was
2.2% and 7.1% on fertilized and unfertilized plots, respectively.
The experience gained by Selectia RIFC during the last 70 years (and farmers'
experience) demonstrates the value of using crop varieties that are well adapted
to local conditions. Use of appropriate crop rotation also reduces dependence on
imported seed, including genetically modified seeds. There has been a lot of discus-
sion about adaptation to global warming using varieties and hybrids with higher
tolerance to droughts. The increased risks of drought under a changing climate can-
not be ignored. Thus, it is also pertinent to take into account soil conditions and the
strategy to enhance soil water storage in the root zone for reducing vulnerability to
drought and decreasing expenses to install irrigation facilities.
The goal of increasing yields and profitability has been implemented since the
1960s through a package of practices: new varieties and hybrids of field crops; inten-
sive, mechanized tillage; monoculture or short-duration specialized crop rotations;
irrigation; and fertilizers and chemicals for pest, weed, and disease control. Such
packages minimized the importance of inherent soil fertility, specifically that of
SOM. Indeed, data from the Selectia long-term field experiment with different crop
rotations and continuous cropping for >50 years show losses of SOM under crop
rotations with different intensity or frequency of row crops and under continuous
winter wheat and maize ( Table 9.4 ).
Even crop rotation with 30% of alfalfa and 4 Mg/ha of FYM over the crop rota-
tion could not compensate for the annual loss of SOM (Boincean 2013a). The same
is true for the long-term field experiments with different systems of soil tillage, fer-
tilization, and irrigation in crop rotations.
In general, long-term field experiments in many countries have been aimed at
studying one or two factors, very often in large gradations, without their integration
into the framework of a farming system. The original Selectia long-term field experi-
ments were no exception. Indeed, the industrial intensification of agriculture was
stimulated by a reductionist approach to farming systems research. A more holistic
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