Agriculture Reference
In-Depth Information
Table 3.2
Interval of crops due to incompatibilities or biotic factors (Müller 1988)
Crop
Year
Incompatibility
Viruses
Fungi
Nematodes
Insects
Winter wheat
2
✓
✓
Winter barley
1-2
✓
✓
Spring barley
0-1
✓
Oats
3-5
✓
Winter rye
0-1
✓
Potatoes
3-4
✓
Sugar beet
4
✓
✓
Rape
3
✓
✓
Field peas
4
✓
✓
Flax
6
✓
✓
Faba beans, lupins
3
✓
✓
✓
Lucerne
4-5
✓
✓
Red clover
6
✓
✓
White or yellow
clover
2-3
✓
✓
Grass-clover
3-4
✓
✓
Cabbage spec.
3-4
✓
✓
Celeriac
3
✓
Leek
2-3
(
✓
)
✓
Carrots
3-4
(
✓
)
✓
Onions
4-5
✓
✓
by spring crops. The time-span between pre-crop harvest and subsequent crop sowing allows
sufficient time for accurate seedbed preparation, intensive mechanical weeding if necessary,
and substantial root development and above-ground biomass for soil protection.
In response to the needs of different farm types, the proportion of the various crop groups
used on the rotation will vary slightly (Table 3.3). Mixed farms with ruminants produce mainly
rough fodder that can be part of the rotation of between 30 and 50% grass-clover or grass-
alfalfa mixtures. Monogastric animals such as poultry and pigs are mainly fed by grains of
legumes and cereals. Therefore, the proportions of legumes and cereals are shifting more to
cereals and from forage to grain legumes. On arable farms the need for forage legumes is
diminishing from the economical point of view. But from the perspective of sustainability,
these farms should stay on at least a one-year set-aside system (Fragstein 1996). Cooperation
between mixed farms (preferably organic) could expand the forage legume segment from one
to two years, enable the import of animal manure as a substitute for the produced and exported
forage fodder, and could keep the farm arable with great benefits for labour management
(Nauta
et al.
1999).
An alternative series of favourable rotational pairs are described by Baeumer (1992),
although these need to be adjusted for specific site and crop conditions (Table 3.4). In more
arid zones, spring cereals can be better suited than winter cereals. If harvest periods tend to be
too late for the timely sowing of succeeding crops, early maturing cultivars have to be chosen
for cultivation. Depending on soil moisture conditions, cover crops may be integrated into the
rotational plan instead of partial fallows. Their value cannot be assessed only by narrow
economic criteria. Indirect effects become more obvious over the longer term, including
