Agriculture Reference
In-Depth Information
efficient production and more pretentious marketing. In the USA, 47% of the certified organic
area was devoted to field and fodder crops in 2003, compared to 34% to pastures and 8% to
fruit and vegetable crops (Economic Research Service, USDA).
In many cases farmers introduce into organic farming the old varieties and land race popula‐
tions of cereals, because of their better resistance on plant diseases and due to their low fertilizer
inputs, but also the yields are lower. Instead of common wheat often grown are spelt, emmer
and einkorn in Austria, Switzerland and Slovenia. In spite of high inputs and low resistance
on plant diseases, the new (modern) cultivars have changed many of their characteristics (grain
size and leaf area have increased almost twenty times, ageing of top leaves has become slower
and the period of assimilate accumulation in grains has been extended, better expressed
productive tillering by cereals, cereals were bred to produce short-stem varieties to prevent
lodging, …).
The competitive strength to weeds is highest for rye, less so for winter barley, oat and triticale,
while wheat and summer barley are the least competitive species, due to their height of steams.
Monocotyledonous weeds like couch grass (
Elytrigia repens
L.), wild oat (
Avena fatua
L.), hair
grass (
Apera spica - venti
L.) and some dicotyledonous weeds like catch weed (
Galium aparine
L.) and perennial weeds like field bind weed (
Convolvulus arvensis
L.), bull thistle (
Cirsium
arvense
L.), etc. are associated in cereals. Maize is associated with other group of wide-leaved
- to the high temperatures sensitive annual weeds like amaranths (
Amaranthus
sp.), white
goose foot (
Cheopodium album
L.), and perennial weeds. Weeds in cereals result in difficult
harvesting and cause an intensive spreading of weed seeds and decrease the yield; and
additional influence of weeds in maize is suppression of growth in the first leaf stages (Maier
code 21-26, [4]).
In organic farming, especially early in the spring at the tillering stage (EC 22-23, see growth
stages of cereals described by Zadoks [5] of winter wheat and barley, lack of available nitrogen
in the soil is problematic, due to nitrogen leaching and lack of mineralization caused by low
temperatures. Rye and oat are less demanding, and thus more suitable for organic production.
Also in case of maize the lack of nitrogen in the spring time is a usual problem.
1.1.2. Position in a crop rotation
Success of cereal crop production primarily depends on the choice of the previous crop,
especially in less fertile soil. In conventional farming systems, there is a possibility to com‐
pensate for a less suitable foregoing crop by using higher rates of fertilizers and pesticides, but
in organic farms, residual soil fertility from crop residues primarily determines the potential
yield of a cereal crop. Rotation is also essential to prevent the build-up of pests and diseases;
in particular foot and root rot diseases.
In mixed farming systems (incl. animal and crop production) where a grass/clover ley is part
of the rotation, cereals can be grown after incorporation of the grass/clover mixture or after a
more N-demanding intermediate crop grown after grass-clover incorporation, such as
potatoes. In stockless farming systems (without livestock), legumes, cereal-legume mixtures,
root crops, or oil seed crops are suitable foregoing crops, provided sufficient N is left from the
