Agriculture Reference
In-Depth Information
approach of higher agrobiodiversity through more natural, wild f flora components in a field.
Weeds are widely reported as a major constraint in organic production and severe crop losses
can be experienced, particularly during conversion and in phase changes in rotations (e.g.
from pasture to arable cropping). A review of plant pest and diseases in organic farming is pre-
sented in the following chapter.
While many important generalisations can be made about soil processes, plant growth and
so on, the performance of particular farming systems, cropping rotations and crop varieties
will always be determined by the local conditions. Historically, most of the research into
organic farming has been conducted in western Europe, the home of modern organic agricul-
ture. However, when the environmental and market conditions are different to those experi-
enced in western Europe, organic farmers need to be innovative and incorporate local
knowledge (e.g. Augstburger
et al
. 2002, Jambhekar 2003).
Crop rotations
The central role of crop rotations in organic farming is highlighted by the important focus on
rotations in many organics certification standards. For example, in the United Kingdom (UK),
the standards for plant production (including pastures) require a 'multi-annual rotation pro-
gramme' for building soil fertility and managing weeds, pests and diseases (Advisory Com-
mittee on Organic Standards 2004). Wijnands (1999) provided a description what a crop
rotation means and how it should be implemented on an organic farm:
Crop rotation is the term used to [indicate] that crops are grown over time in a
very specific order. After a number of years (length of the crop rotation), the cycle
will be repeated. The crops grown in one year on the available area of a farm make
up the cropping plan. If the crop rotation is consistent and unchanged, the
cropping plan is the same every year. Crop rotation has a temporal aspect [where]
crops are grown over time in a specific order (succession of crops in time); and a
spatial aspect [where] the crops grown this year and their division over the
available space. The interaction between spatial and temporal aspects can be used
to strengthen the crop rotation concept. Rotating the crops on the available space is
done so that a given crop is never grown next to a field with the same preceding
crop (spatial crop rotation). This helps to prevent semi-mobile pests and diseases
from surviving from one year to the next.
The aims of crop rotations in organic farming systems were summarised by Kahnt
et al
.
(1997):
• maintenance and improvement of soil fertility
• maintenance and improvement of soil organic matter
• maximisation of symbiotic N fixation through cultivation of forage and grain legumes
• production of sufficient food and straw for animal husbandry
• optimised use of pre-crop effect through crops with high gross margin
• mobilisation of nutrients through crops with high root density and root depth
• control and reduction of pests and diseases
• control of weed competition combined with gentle soil cultivation
• improvement of time management for crop husbandry-specific labour
• maintenance and improvement of the economic situation of the farm.
In mixed farms, the crop rotation is mainly focused to provide enough fodder for the dif-
ferent animal species. Therefore, the rotational plan will react to market demands only to a
