ABSTRACT
Improving water management in organic crop cultivation Michael J. Goss, University of Guelph, Canada; Adrian Unc, Memorial University of Newfoundland, Canada; and Wilfried Ehlers, Georg-August University, Germany
1 Introduction
2 Key aspects of organic farming affecting availability and use of water
3 Developments in water management in organic agriculture
4 Conclusion
5 Where to look for further information
6 References
1.1 Water on earth and in the atmosphere The global water cycle gives a simple overview of how water associated with the soil, geological substrata, plants, animals and the atmosphere link to each other. As plants largely, but not uniquely, exploit water in the soil we need to understand how they are able to access this resource and know how large a volume is available. However, soil and plants also lose water to the atmosphere and hence the balance between these three parts of the cycle is critical for identifying whether and how the losses can be replenished, either in the short or long term. Water may seep through soil and into underlying rock strata, which can represent an important mechanism by which nutrients may be lost by leaching from the rooting zone of a crop. In some circumstances, this can be beneficial because it prevents the build-up of salts and the development of salinization. There are times when water needs to be removed from soils through constructed drainage schemes, for example, when there are barriers to natural drainage that cause waterlogging. This can prevent roots from exploring a sufficiently large volume of soil to anchor plants and capture enough mineral nutrients. If soils are not sufficiently permeable, incident rainfall may be so intense that water cannot infiltrate but flows from the field over the soil surface, which can lead to erosion and loss of mineral and organic matter fractions of the soil. We therefore have to consider both the static and dynamic aspects of water availability in the soil.
