Developing no-tillage systems without chemicals: the best of both worlds? - Organic Agriculture: A Global Perspective - page 83

Special topic 1
Deeloping no-tillage systems without chemicals:
the best of both worlds?
Ron Morse*, Virginia Polytechnic Institute and State University, USA and Nancy Creamer, North
Carolina State University, USA
*Prof Emeritus Ron Morse, Vegetable Crops Research, Department of Horticulture, Virginia Polytechnic Institute and State
University, Blacksburg, Virginia 24061-0327, United States of America. Tel: [phone], Fax: [phone],
Email: [e-mail]
Introduction
While demand for organic produce is high, growers throughout the world face a potentially
serious dilemma. Although most organic producers are concerned with soil quality including
the physical, chemical and biological properties of soils, they generally use multiple inversion
tillage operations (ploughing, disking, cultivation) for seedbed preparation, incorporation of
cover crops and weed management. These practices can degrade soil quality. Labour and input
costs in organic systems are often high because organic growers cannot use low-cost chemicals
to control weeds and supply nutrients (Berry et al . 2002, Walz 2004). In addition, because of
reliance on inversion tillage, organic farms can suffer greater soil losses than chemical-based
no-till systems (Bruulsema et al . 2003).
Organic high-residue reduced-till systems
High-residue reduced-till systems (HRRT) offer great potential to resolve the soil quality/high
tillage cost dilemma associated with organic farming (Bàrberi 2002). Ideally, HRRT is an
integral part of an holistic approach to organic farm management that generates both short-
term productivity and profitability and long-term production capacity (sustainability). An
ideal organic HRRT system can simultaneously provide:
1 synchrony of nutrient supply with crop demand; and
2 multiple non-nutrient effects, including weed suppression, soil aggregation, resistance to
erosion, biological pest management, and water infiltration and availability (Berry et al .
2002, Magdoff and Weil 2004).
Based on grower experiences and research data, the core components of HRRT for organic
growers are:
1 regular use of grass and legume cover crop mixtures;
2 permanent soil coverage with either dead or preferably living plant residues - derived from
diverse rotations of cash crops and high-residue cover crops; and
3 strategic limited number of soil disturbance events (tillage with a purpose), employed to
manage weeds, regulate rate of decomposition of organic substrates and optimise soil tilth
and plant establishment.
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