Agriculture Reference
In-Depth Information
Are there any differences between tillage management in
organic and conentional agriculture?
A logical assertion that could stem from what has been reported in the previous paragraphs is
that hardly any differences can be seen between the theoretical approach to tillage manage-
ment in conventional and organic agriculture. This is true if it is assumed that agroecosystem
management, including tillage, should always be based on good agronomic practices regard-
less of the production system. In practice, however, there are some differences that are more
related to cropping system structure and effect rather than to tillage itself. In a given context,
organic cropping systems are invariably more diversified than their conventional counterparts
(Stolze
et
al
. 2000). The inclusion of more crops (including cover crops) in a rotation usually
results in consequent diversification of tillage practices, either because requirements (e.g. for
soil penetration resistance) may differ depending on type of cash crop and useful product (e.g.
grain v. root crops) and/or because cover crops may need some degree of incorporation in soil
to exert their positive agroecosystem functions (e.g. nutrient release).
In addition, organic systems usually enhance soil physical and biological fertility in the
long term compared to conventional systems, such as aggregate stability, soil A horizon depth,
organic matter content, porosity, earthworm abundance and activity, microbial biomass
carbon (C) and N and their ratios to the total and light fraction C and N pools in soil, lower N
microbial turnover rate and soil colonisation by mycorrhizae (Gerhardt 1997; Siegrist
et
al
.
1998, Fließbach and Mäder 2000, Mäder
et
al
. 2000, Pulleman
et
al
. 2000, Friedel
et
al
. 2001).
These effects, which cannot easily be attributed to one or more specific agroecosystem compo-
nents (including tillage) but rather to their positive interactions, by being beneficial to agroec-
osystem production, stability and resilience, can also bring about a new vision of tillage
management. In a more stable and resilient agroecosystem it can be assumed that the potential
disrupting effect of any disturbances, including tillage, would be buffered. Therefore, the
degree of detail that should be paid to tillage management in an organic system is negatively
correlated to the degree of stability and resilience of the system itself.
Skilled organic farmers know well that they have to integrate tillage management into their
cropping system management strategy. Surprisingly, this integration is less obvious when
examining the organic research literature, although there are exceptions. One of them is the
so-called 'punch planting' method, also developed in Denmark. With this method, a hole is
punched in the soil and a seed is dropped into it, without any seedbed preparation and soil dis-
turbance outside the hole (Rasmussen 2003). Although this system has been developed mainly
to improve in-row weed control (coupled with stale-seedbed and f flame weeding) in row crops
(e.g. fodder beet), it has also proved beneficial to soil tilth preservation. Conversely, Drinkwa-
ter
et
al
. (2000) observed that compared to no-till management, post-emergence cultivation
for direct weed control in maize also increased mineralisation of vetch residues, thus increas-
ing N supply during maximum N demand by the crop.
Conclusions and future perspecties
It is not possible to generalise the effects of tillage management, since the positive or negative
features depend largely on the agrienvironmental context and on cropping system structure.
This is even more so in organic agriculture, where cropping system management cannot (and
must not) be standardised, unlike what is usually done in conventional systems. It would be
desirable to see more scientific projects and publications about not only the development of
innovative, non-inversion tillage systems, but also with their actual integration in organic
cropping systems planning and management. There is a discrepancy between the overall agree-
