ABSTRACT
Maintaining soil fertility and health in organic crop cultivation C. Watson, Scotland’s Rural College (SRUC), UK and Swedish University of Agricultural Sciences, Sweden; and E. A. Stockdale, Head of Farming Systems Research, NIAB, UK
1 Introduction
2 Some key themes in soil fertility and soil health
3 Case study: interactions between soil management and the delivery of soil functions/ecosystem services
4 Conclusion and future trends
5 Acknowledgements
6 Where to look for further information
7 References
The concept of soil health is deeply embedded in organic agriculture as reflected in Lady Eve Balfour’s statement ‘The health of soil, plant, animal and man is one and indivisible’ (Balfour, 1943). But what do we really mean by soil health? Here we use the integrative concept of soil health, closely related to soil quality, which reflects the capacity of a soil to respond to agricultural management practices and maintain agricultural production amongst a range of other ecosystem services (Kibblewhite et al., 2008). This definition of soil health can be seen as an agricultural interpretation of the overarching FAO definition of soil health ‘the capacity of soil to function as a living system’ (FAO, 2011) compared with soil quality which has been defined as its fitness for a given use (Larson and Pierce, 1994). Soils in cropping systems both give and receive ‘supporting’ and ‘regulating’ ecosystem services while providing ‘provisioning’ services (Fig. 1). Ecosystem services are normally regarded as positive (+); however, agricultural soils also create some negative (−) ecosystem services or ‘disservices’ which can be viewed as a negative feedback loop to ‘regulating’ and ‘provisioning’ services. In managing soil within organic farming systems, our aim must be to minimise these disservices while providing the healthy soils needed to deliver adequate ‘provisioning’ services. The capacity of a soil to maintain agricultural production or soil fertility (Cooke, 1967) encompasses not only the provision of crop nutrition but also plant disease prevention/plant health promotion and is thus a component of soil health. Soil fertility can therefore be seen as an aggregate of soil biology, chemistry and physics as illustrated in Fig. 2, which shows how the incorporation of crop residues can influence soil
fertility through effects on biology, chemistry and physics (Stockdale and Watson, 2012). The extent to which soil fertility can be manipulated and the rate at which changes occur will depend on fundamental properties such as soil texture and parent material, and also on climatic conditions. Many possible indicators and indexes of soil health are described in the literature (see, e.g. Kelly et al., 2009; Idowu et al., 2008), and there is currently much interest in the development of improved tools to communicate the complexity of the impacts of soil management and to allow farmers to develop locally adapted approaches to maintain soil health (Stockdale et al., 2017).
