Agriculture Reference
In-Depth Information
In this chapter we specify the need for better adapted varieties, and describe possible eco-
logical and ethical approaches to develop such varieties, and the attempts made to develop
organic propagation of varieties to close the chain and refrain from conventionally produced
inputs.
Variety characteristics
Variety choice in organic farming is an essential factor of successful production. But there is a
significant lack of information on the performance of varieties under organic conditions. As
conventional plant breeding aims at optimising yields under high inputs, the conventional
variety testing selects for high performance under high input conditions. As the diversity of
organic farming systems and conditions is large and results in a larger genotype-environ-
ment-management (G × E × M) interaction than in conventional agriculture, the organic
farmer is more interested in varieties that have the ability to adapt to variable conditions and
perform well with stable yields in different years at the specific site. In many countries there
are variety trials under organic conditions but not for every crop and every year. Some are con-
ducted by farmer groups, others by research stations or by commercial seed companies.
Yield stability and plant health
Long-term trials show that yields f fluctuate much more in organic agriculture than in conven-
tional agriculture. This is ref lected by a larger coefficient of variation (Lammerts van Bueren
et al
. 2002, EFRC 2004). For some crops this year-to-year variation has become one of the most
important factors that limits the growth of the organic market share (Spiertz 1989, Raupp
1996, Tamm 2000, Mäder
et al
. 2002). To reduce risks and increase yields the organic farmer
first of all aims at system stability. That can be done through improving agronomic strategies
and selecting appropriate varieties. For many crops one of the limiting factors inf luencing
yield stability is the suitability of the available varieties. Organic farmers would rather have a
variety with a reasonable yield and good stress tolerance than a variety that promises higher
yield but largely loses that yield increase because of, for instance, disease susceptibility. Reliable
varieties are those that can cope with unfavourable weather and soil conditions (e.g. f luctuat-
ing mineralisation rate of nutrients, assessed over several years). Farmers look for varieties that
are, in general, more f flexible and robust to support the self-regulating capacity of the organic
farming system.
Conventional breeders often think that organic farmers require an absolute disease resist-
ance, but in many cases tolerance or partial resistance can be sufficient. Organic farmers are
used to searching for ways to reduce risks by an array of solutions at different levels (farm,
crop, variety) and also adopt such a strategy in their search for appropriate combinations of
supporting variety characteristics. There are different variety characteristics that support yield
and yield stability through optimal plant health (Table 5.2). Plant health can be defined as a
result of the following components:
1 escape - the crop is not exposed to a certain pest or disease;
2 resistance - the crop is exposed to the pest or disease but is not affected;
3 tolerance - the crop is affected by the pest or disease, but with a limited effect on the yield;
and
4 ability to recover - the affected crop is able to recover to a certain extent.
Product quality
In the organic sector, the non-chemical approach also has effects on traits concerning product
quality, such as long-term storability without chemical sprouting inhibitors for onions
