Agriculture Reference
In-Depth Information
Special topic 4
Tillage: how bad is it in organic agriculture?
Paolo Bàrberi*, Land Lab, Sant'Anna School of Advanced Studies
*Asst Prof Paolo Bàrberi, Land Lab, Sant'Anna School of Advanced Studies, P.za Martiri della Libertà 33, Pisa 56127, Italy.
Tel: +39 050 883525, Fax: +39 050 883512, Email: barberi@sssup.it
Introduction
Soil tillage is often perceived to exert negative effects on organic farming systems. This percep-
tion likely stems from the consideration that tillage can deteriorate soil structure, disrupt eco-
logical niches for soil biota (e.g. earthworms and vesicular-arbuscular mycorrhizae) that have
positive ecological functions in agroecosystems, enhance soil organic matter (SOM) minerali-
sation and impair SOM build up, increase risks of nutrient losses to the environment and of
soil erosion and ultimately contribute to soil fertility loss and soil quality degradation.
However, it would be incorrect to claim that soil tillage
per
se
is the cause of these negative
effects. Indeed, such effects are more appropriately associated with repeatedly wrong technol-
ogy application, such as the blanket use of deep mouldboard ploughing regardless of crop and
environmental context, as it has been the typical long-term situation in conventional systems,
like continuous wheat cropping in Southern Europe (Bàrberi and Lo Cascio 2001).
As the negative effects of tillage are often associated with conventional agriculture, and as
one of the main goals of organic agriculture is to counteract and/or prevent negative aspects
related to conventional systems management, it would seem logical to always associate organic
systems management with tillage reduction. The aim of this chapter is to challenge this dogma
through a reasoned analysis of the pros and cons of tillage in organic agriculture based on the
rather scant scientific literature available, and underlining the need to conceptualise tillage
management in a cropping system and environmental context. Lastly, differences between the
expected effects of tillage management in conventional and organic systems will be
discussed.
When tillage is important in organic agriculture
Organic systems rely on the application of organic amendments, green manures and other
organic matter sources with the dual purpose of:
1 building up soil fertility through an increase in SOM quantity and quality; and
2 supplying adequate amounts of nutrients, especially nitrogen (N), to sustain crop growth
and productivity.
This indirect approach to crop fertilisation, which clearly ref lects the preventive, long-term
nature of agronomic recommendations set forth in organic systems (IFOAM 2005), increases
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