Contents
    Summary
    Chapter One
    Chapter Three
    Chapter Four
    Chapter Five
    Chapter Six
    Chapter Seven
    Chapter Eight
    Chapter Nine
    Chapter Ten
    Appendices
    Foot Notes     

A project facilitated by the Research and Development Group of the Bio Dynamic Farming and Gardening Association

2 The Soil System: The Development and Functions of Soil

Soil is a living system that represents a finite resource vital to life on earth. It forms the thin skin of unconsolidated mineral and organic matter on the earth’s surface. It develops slowly from various parent materials and is modified by time, climate, macro- and micro-organisms, vegetation, and topography. Soils are complex mixtures of minerals, organic compounds, and living organisms that interact continuously in response to natural and imposed biological, chemical, and physical forces.

(Soil Science Society of America, 1995, Agronomy News,
June 1995).

To understand the soil we need to know its function as a system as well as a systems component of the larger agro-ecosystem and ecosphere. In biological terms we need to know the organism’s function as a whole as well as the function of the organs in the organism. Soil is both an organ, in relation to the wider farm ecology, and an organism when considered in relation to its own organs (sub-units), which might be minerals, organic matter, micro-organisms, etc.

Soil systems and soil systems components have properties that are expressed by the whole but not by the sum of their parts. These emergent properties cannot be predicted by studying the components in isolation or decoupled from the whole (Odum, 1997, Checkland, 1981), as this provides a distorted picture This review provides an insight into the interactions that relate to the soil as a system and the soil as a component of the larger whole. The function of the soil is discussed first.

The soil is then reviewed as part of a larger system namely, the agro-ecosystem and landscape.

The systems components of the soil – this soil biota, soil nutrient cycling and diversity – are then discussed. These components work together as a functional whole – the earth’s life supporting system. In this way, some emergent properties of the earth’s life supporting system can become clearer. There are no clear boundaries between the different components e.g., between soil biota and the soil system, which leads to some repetitiveness and overlap in conclusions drawn, but also to some fresh insights from different angles.

What is the Function of a Soil?

The soil’s principal function is to support the development of a landscape or ecosystem, in other words, together with air, sun and water, the soil is a major life-supporting component of the ecosphere. The development of an ecosystem begins with a soil of purely geological origin, later called the soil parent material. The introduction of water to this geological material starts chemical actions influenced by the environment (climate, topography, flora and fauna). This physical and chemical system then evolves further towards an increasingly complex ecological system. Ecological processes in the soil become increasingly obvious and complex, and this increases the soil’s functional stability or independence from environmental fluctuations, giving increasing autonomy to the systems.

The development of the soil system in time and space is accompanied by a concurrent development in the ecosystem or landscape. The development of flora and fauna on and in the soil is called ecological succession. Both have evolved together as a system, and the following soil functions can be seen as emergent properties of this development. Under natural conditions, the soil:

• sustains biological activity, diversity, and productivity;
• regulates and partitions water and solute flow;
• filters, buffers, degrades, immobilizes, and detoxifies organic and inorganic materials, including industrial and municipal by-products and atmospheric depositions;
• stores and cycles nutrients and other elements within an agro-ecosystem and the earth’s biosphere.

Through these functions the soil system acts as the chief organizing centre, since all ingredients necessary to sustain primary and secondary production are stored in and recycled through the soil. Ecological succession is also a way to restore ecosystems after storms, fires or other periodic catastrophes have devastated the landscape. During ecological succession from early stages to maturity and beyond, the soil’s biochemistry (e.g.. ‘digestive system’ or ‘metabolism’) changes. This change in biochemistry is directed (Odum, 1969 & 1997) by the community (soil life) and limited or patterned by:

• the geological origin, or parent material, of the soil; and
• the environment (climate topography).

This means that over time the physical, chemical and biological characteristics of soil change. The main biological components of soil are:

• the food web, the largest contributor to the biochemistry, develops from being relatively simple and linear in the early stages of soil development and ecosystems succession to becoming increasingly complex in the mature stage;
• soil organic matter, which increases as soil develops. The rate of humus formation reaches a state of equilibrium in the mature stage, which is then maintained (Bokhorst, 1992) until old age or degeneration approaches.

The soil food web largely depends on soil organic matter. The organic matter provides food and structure in the soil, creating optimum conditions for the soil food web, which develops along with humus formation and the succession at the soil surface.

Table 1 (Appendix 1) shows the trend in ecological development (Odum, 1997).

Table 1 shows the function of a soil in an ecosystem. From a chemical perspective the soil develops from being mainly mineral towards a ripened or developed soil, reaching a steady state in humus content. In these early stages of development, the Cation Exchange Capacity (CEC: nutrient storage) of the soil increases. Young soils are high in inorganic phosphorus, as soils matures inorganic phosphorus decreases while on the other hand organic phosphorus is formed and increases, reaching an optimum level in the mature stage. Leaching of cations lowers the pH in the early stages of development (van Steensel, 1998; Bokhorst, 1992; Molloy, 1993). These chemical aspects reach an optimum during the mature stage. The CEC, the balance between organic and inorganic phosphorus and the pH stabilizes.

Maturity is reached with the achievement of an approximate steady state, meaning that:

• the mineral cycles have become efficient or (semi-) closed;
• turn over and nutrient storage has increased; and
• the internal cycling and nutrient conservation has improved.

In a mature ecosystem, gains equal losses over a long period.

As soils age, nutrients may leach out faster then they accumulate; impervious layers may form and restrict root growth, resulting in less biomass production and humus formation. Old age is approaching; the soil degenerates (van Steensel, 1998; Bokhorst, 1992). The time from juvenile to old age is from 0 to 50 000 or 100 000 years, depending on soil type, topography and climate.

These developmental characteristics are recognizable and quantifiable. Some parameters and benchmarks have been established but further parameters are required to manage and monitor soils in an ecologically sustainable manner. These parameters can then provide a basis for a more progressive agriculture, based on deductive/analytical science, but one that also takes into account the time-space continuum and its ecological development. Some quantifiable parameters could be:

• humus content: The soil evolves from having no or low humus content to a balanced optimal level in the climax stage;
• biological activity increases during the developmental phase to an optimum or steady state in the mature phase;
• community structures or food web characteristics: As a system matures the microbial population evolves from limited numbers of fungi to increased numbers of fungi in the climax or mature stage (Ingham, 1990).

This area requires more research.

The Soil System and Agriculture

Soil development has resulted in a wide diversity of landscape or ecosystems at different times of their development; based on different parent material; under different environmental conditions; leading to a relatively stable, diverse, life supporting healthy biosphere.

Theoretically, soil systems should support a broad diversity of land-use systems. Natural boundaries have to be recognised (land suitability mapping). These are demonstrated to some degree in New Zealand by the diversity of agricultural and horticultural systems in different parts of the country (e.g., the Crops for Southland project promoting crops on matching soil type and environmental conditions as a form of diversification). However, over the last century there has been an accelerating trend towards specialization and monocultures. Landscapes in many countries, especially countries with intensive agriculture, are becoming increasingly uniform in appearance. Concern over biodiversity loss is now an issue of global importance, closely linked to another issue of global concern: soil degradation involving organic matter decline, erosion, acidification and environmental pollution. From an ecological perspective, the removal of natural systems and their replacement with large-scale, high input monocultures has set back or stopped soil development, as systems properties and functions are lost. To maintain those systems requires high inputs involving high energy costs. By underestimating the effect of the time-space continuum (soil development) and the environmental influences on the soil system, mainstream agricultural soil systems have lost part of their function, leading to declining soil quality that contributes:

• increased cost of production;
• environmental degradation;
• loss of diversity;
• reduced plant and animal health;
• reduced human health.

Pioneers of the organic and biodynamic methods (Pfeiffer, Albrecht, Voisin, Howard, Steiner) recognised these consequences. Their scientific efforts and extensive experience can be summarized as follows: if the soil system functions only partly, for instance with limited biochemistry (lack of functional soil life), then plants will be short-changed nutritionally and, as a logical consequence, so will the dependant food web (animal and human life forms).

Every farm has its own individuality, depending on its soil parent material, its environment, its place on the time-space continuum and its socio-economic context. Rather than a high input-output system as in conventional farming systems, organic systems represent throughput systems with the emphasis on optimum and quality production as opposed to maximum production.

The wider acceptance of this view is recognized in various new scientific disciplines, research methodologies and farming methods. These are more holistic and integrative approaches to science and society, and contribute to a paradigm shift. The new scientific disciplines and concepts like soil quality, (agro) ecology, biochemistry, biophysics, and systems thinking are all part of this shift, and so are the new farming methods like ecological, biodynamic, organic and natural farming. A further extension of this shift is the introduction of new research methodologies, such as on-farm, farmer-orientated or participatory research, and phenomenology (or Goethean science). These methodologies are described in the section on research approaches. A clarification of the paradigm shift from a soils point of view is given in Appendix I.

Soil Quality

Recognition of the concept of soil quality illustrates a shift towards soil biology – a more ecological view, and includes:

• soil organic matter and humus dynamics, including nutrient dynamics (Kubat, J, 1991, Doran et al., 1992; Doran, 1996; Pankhurst et al., 1997);
• rhizosphere dynamics (Pankhurst et al., 1994; Ingham, 2000);
• soil food web dynamics (Ingham 1999; Elsas, van der et al., 1997).

These aspects contribute towards a better understanding of site-specific soil characteristics and function, recognising the soil’s complexity and intrinsic value.

The Soil Science Society of America (1995) adopted the following definition of soil quality:

Although unstated, the above definition also presumes that soil quality can be described by a unique set of characteristics for every kind or type of soil. It recognizes diversity amongst soils, and that a soil with excellent quality for one function or product can have very poor quality for another. Soil quality in its broadest sense is enhanced by land-use decisions that weigh the multiple functions of soil, and is impaired by land-use decisions that focus on single functions. Soil quality can be degraded by using inappropriate tillage and poor cropping practices; through excessive livestock grazing or poor timber harvesting practices; or by misapplication of fertilizers, animal manures, irrigation water, pesticides, and municipal or industrial by-products. To enhance soil quality, farmers, consultants and researchers should recognise that soil resources affect the health, functioning, and total productivity of all ecosystems.

The concept of soil quality looks beyond soil fertility and maximum production; the definition stresses the importance of system maintenance (van Steensel, 1995; Hill, 1994). To sustain system maintenance, basic soil quality indicators that can identify soil management problems from the perspective of the soil’s functions and development are needed to monitor the effects of soil management. Such indicators are generally under utilised in today’s agriculture, although there is an increasing recognition of their need. A good starting point is the visual soil assessment guides produced by Landcare Research (Shepherd, 2000).

Research Review

A functional structure is required to put into perspective the fragmented research efforts in the area of organic soil management. The available organic literature is divided into topics relating to soil system functioning, exploring the ‘organic’ research activities in New Zealand and comparing them with the overseas research activities on organic soil management as far as possible.

• Soil quality.
• Soil organic matter, soil biota , nutrient cycling.
• Landscape quality and organic soil management.
• Biodiversity and farming.
• Orchard soils and organic soil management.
• Pasture soils and organic soil management.
• Soil-plant-animal/human health.

The review is far from complete and has a strong European influence (Dutch and German). It represents a general picture of the current states of affairs in organic research and research methodology.

Soil Quality and Organic Soil Management

Soil quality is the most important indicator of the usefulness of organic soil management methods. The quality and health of soils determine agricultural sustainability (Acton and Gregorich, 1995), environmental quality (Pierzynski et al., 1994) and, as a consequence of both, plant, animal and human health (Haberern, 1992).

Studies of soil quality in New Zealand

One of the first and probably most cited research paper on soil quality and organic farming systems has its origin in New Zealand. The Reganold Report (1993) highlights the advantages of biodynamic farming systems as opposed to conventional farming systems with regards to soil quality aspects. The report compared soil properties on seven pairs of biodynamic and conventional systems. Soil structure on the biodynamic farms was significantly better than the soil structure of their conventional counterparts.

Soil structure is an undervalued factor in agriculture. It has great significance for plant (root) growth and rhizosphere development. As soil structure is the result of the interaction of soil life with the soil environment, the conclusion that the organic farms had higher (micro) biological activity than their conventional counterparts is not a surprise. Higher levels of earthworms, soil respiration, mineralisable nitrogen and the ratio of mineralisable nitrogen to organic carbon confirmed the situation. In 1994, Macgregor concluded:

Similar conclusions were reached by van Steensel (1995): that the pasture phase in organic crop rotation had better soil quality aspects then the pasture phase in conventional crop rotation. The next key New Zealand report (Murata & Goh, 1997) to compare organic and conventional soil management reported that: total carbon, total nitrogen, microbial biomass carbon and microbial biomass nitrogen were increasing and higher in organic crop rotation under the pasture phase compared with the pasture phase under conventional rotation. These parameters decreased less during the cropping phase under organic soil management than during the cropping phase under conventional soil management. Simply, there were more micro-organisms and more food for micro-organisms, which resulted in higher biological activity under organic soil management. High biological activity is not necessarily better (as explained later) but in the above comparisons it indicates an improvement in soil functioning and development.

Condron et al., (2000) reviewed soil quality under organic and conventional farming systems and concluded:

International studies of soil quality

Overseas comparison studies show similar results to the New Zealand studies: generally improved soil quality under organic soil management compared to conventional soil management (Liebig & Doran, 1999; Stamatiadis et al.,1996; Gardner et al., 1996). A long-term comparison trial by the Rodale Research Centre (Doran, 1994) also draws the conclusion that there is higher biological activity in the organically managed system as demonstrated by higher soil respiration, faunal populations and water infiltration rate.

Studies on soil quality aspects

Soil fertility, a soil quality indicator, is considered to be improved by organic farming systems, because it depends on a recycling of nutrients and a proper balance between organic material, soil organisms, and plant diversity that maintains a productive soil (Deavin, 1978; Lopez-Real & Hodges, 1986; Arden-Clarke & Hodges, 1988). Higher soil organic matter contents have been found to have positive effects on yield and yield components of cereals (Gorlitz & Asmus, 1984; Schnieder, 1984; Gorlitz, 1986) as well as on physical charac-teristics (Asmus et al., 1987).

Friedel (1999) reports that microbial biomass carbon and nitrogen were significantly higher on long-term organic fields compared with conventional fields. Mader et al., (1999), reporting on their long-term study at FiBL (Research Institute of Organic Agriculture, Switzerland), found a significantly greater soil microbial biomass carbon and enzyme activity on the two organic treatments compared with controlled, conventional and mineral treatments.

Microbial biomass and microbial activities involved in nutrient dynamics can enhance the plant’s nutrient uptake (Elliot, 1994; Ingham, 2000). For example, Oberson et al., (1993) reported the enhancement of phosphorus dynamics in biologically managed systems. The turn-over rate determines the amount of available nutrients, and largely depends on the amount of soil organic matter, humus, microbial biomass, microbial activity, and environmental conditions such as daily and seasonal rhythms.

Improved functional biological activity (Tilman, 1998) often leads to improved soil quality in terms of biological and chemical properties and physical stability (Drinkwater et al., 1998; Mader et al., 1996; Reganold et al., 1987). This is a key aspect of both soil quality (as shown above) and organic farming systems (see below).

Other studies on organic soil management involving indicators of soil quality are:

• on microbial biomass: Fließbach & Mader, (1997); Franzluebbers et al., (1996); Oberson et al., (1993); von Lutzow & Ottow, (1994); Zelles et al., (1992); and
• the physical and chemical properties of soil organic matter: (Fließbach & Mader, (2000); Wander & Traina, (1996).

All these studies indicate that soils under organic management have the potential to contribute to improved soil quality, meaning improvements in:

• sustainability;
• environmental quality and, therefore;
• plant, animal and human health.

The studies on soil quality and soil quality aspects that compared organically managed with conventionally managed farms indicate that the soil system under organic soil management has reached a higher level of functionality and development than the similar soil system under conventional management (i.e., it has more mature characteristics). In Table 1, page 174 it can be seen that this has advantages and disadvantages: e.g., for instance biomass production decreases (less productive) while stability and resilience to stress increase (less inputs required). In the end, it is a trade off the farmer has to make. The ‘organic’ trend would be to opt for more climax characteristics in the farming system:

• to correct the over-emphasis on maximum production and juvenile and developmental characteristics of conventional farming systems;
• to phase out the reliance on agro-chemicals by increased stability and feedback controls

This means an input-output farming system becomes more like a through-put farming system.

To improve soil quality, organic research organisations and institutes (FiBl, LBI, HDRA, Rodale Institute, etc.) explore accepted methods such as more diverse crop sequences, increased crop rotation, inclusion of ley crops and pasture, no tillage and/or reduced tillage, and organic manuring (Anderson & Domsch, 1989; Liebig & Doran, 1999).

As organic farmers do not use soluble fertilisers, and rely entirely on biological nutrient cycling processes (Bloksma, 1996, Kopke, 1997), it is important to know what factors contribute to functional biological activity and turn-over rates of microbial biomass. The organic research centres mentioned work closely with farmers and address practical site-specific questions.

Soil microbial biomass and activity can be significantly increased by crop rotation as well as by additions of organic manures (Anderson & Domsch, 1989; Raup, 2001). Addition of effective and/or plant growth promoting micro-organisms (see for example IFOAM conference papers; Pankhurst et al., 1993) also contributes to this effect.

Soils have an optimum level of microbial activity. Higher microbial activity might result in high mineralisation rates and if this is not synchronised with the plant or plant community demand could result in losses from the soil system. Research is currently being carried out at FiBL on the effect of high microbial activity under practical conditions. Decomposing material will be used to form:

• new microbial biomass (immobilisation);
• labile (available) organic compounds (mineralisation); and
• stabilized organic compounds (humification) in the soil.

(Jenkinson et al., 1987; Parton et al., 1987).

Processes such as immobilisation, mineralisation and humification, (and particularly the net result of these processes in the soil), are important for consultants and producers to understand. A Louis Bolk Instituut report on orchard floor management (Bloksma, 1996) shows the practical implications of the ratio between mineralisation and immobilisation as follows:

As stated in the report written for Dutch growers, researchers and extensionists:

• net mineralisation occurs under relatively warm, aerated, alternately wet and dry, relatively alkaline conditions influenced by the energy supply from crop roots. (Conditions normally prevalent in spring and early summer.) Actions that can be taken to encourage strong mineralisation are: soil aeration, irrigation and drainage, liming, increase of nitrogen supply, e.g., fresh manure, regular mowing of grass, legumes, preparation 500, etc;
• net immobilisation occurs under colder, solid or compacted, constantly wet, acidic conditions with limited plant root activity. (Conditions normally prevalent during autumn and winter.) Actions that can be taken to encourage strong immobilisation are: no aeration, keep moist too wet, no liming, increase carbon supply, e.g., mature compost or lignin or hemicellulose rich material like hay, straw or wood, no legumes in the ley, preparation 501, etc.

The LBI report (Bloksma, 1996) provides useful knowledge for the grower that would be helpful for the grower in New Zealand too. The report demonstrates how Western European ecological research methodology provides practical assistance to growers, enabling them to use the information to develop viable organic systems. Much of the LBI research (participatory research approach) is undertaken jointly with producers on their properties, which means both sides gain relevant knowledge. The producer gains insights into organic farming processes and the researcher gains practical and site-specific knowledge. This has resulted in fast progress and growing confidence in organic farming systems by researchers and growers.

Soil biota, soil organic matter, and nutrient dynamics under organic soil management

Soil biota is a functional component of soil systems, of the farm, and of the ecosystem. Pankhurst et al., (1993/94) clearly state the importance of soil biota:

Organic farming systems (e.g., those described by Balfour, Howard, Steiner, Pfeiffer, Rodale, Albrecht) emphasise living soil, and this includes the importance of soil organic matter, soil biota and food webs in the soil. Brought to general public attention by Rachel Carson’s Silent Spring (1961), our knowledge of the importance of food webs has grown rapidly, along with the understanding developed by ecologists such as Odum (1969). The increasing interest in soil biology and ecology and soil quality means the relevance of food webs for agriculture and horticulture has been recognised (Pankhurst et al., 1993; van der Werff, 1992; Ryder et al., 1993; van Elsas et al., 1997).

One of the most profound aspects of the soil food web is the functioning of the rhizosphere. Rhizosphere soil generally has a higher number and broader diversity of soil micro-organisms, that is a more complex community structure, than the surrounding soil due to the interaction of plants with soil. Plant exudates and organic matter stimulate microbial activity and Ingham states that many plants can be recognised by their rhizosphere community structure (Ingham, 1999, 2000). It appears that every plant species "co-creates" its own rhizosphere population or community structure that aids its nutrient uptake and can by various techniques protect it from potential pathogens (Trevors & van Elsas, 1997; Whipps, 1997; Ingham, 2000). This means that a broad diversity of crops or plants has a more complex community structure of soil biota.

During the development of the soil system, the food web becomes increasingly complex (Odum, 1997; Tugel et al., 2000) (see also Table 1, page 174). In the later stages of the soil and ecosystems development, the role of fungi increases (Ingham, 1999/2000). The same is true for biological activity. Young soils are low in biological activity (simple food web or chains). During the developmental stage biological activity increases (increased food web complexity), then activity stabilises (reaches a relatively steady state that fluctuates with daily and seasonal rhythms) during the climax or mature stage (complex but stable food webs).

As stated in Table 1 an increase in food-web complexity in an ecosystem goes together with:

• a decrease in yield (or net community production);
• (semi) closed mineral cycles;
• increased turnover time and storage of essential elements;
• increased internal recycling;
• increased nutrient conservation;
• increasingly mutualistic behaviour;
• decreased entropy (or reduced losses).

From a soil’s perspective, a similar view is expressed in the Soil Biological Primer (Tugel, 2000), which lists the benefits of complexity including:

• nutrient cycling;
• nutrient retention;
• improved structure, infiltration, and water holding capacity;
• disease suppression;
• degradation of pollutants;
• biodiversity.

The Primer recommends more research into community structures and food web complexity. Microbial biomass and microbial activity in the soil is a soil quality aspect and organic soil management has a positive influence on them. This might be due to an increase in food-web complexity. The hypothesis that the stability of soil ecosystems increases with increasing diversity (maturity) seems to be confirmed by Fleissbach et al., (2001) from FiBL. They suggest that the long-term effects of organic and conventional farming systems result in differences in the soil microbial community structure that lead to differences in the decomposition of organic matter. This results in higher or lower nutrient availability for the crops grown.

The introduction of micro-organisms to the farming system (often termed functional or effective, beneficial or plant growth promoting organisms) is being widely researched. In the USA and Europe compost and composted manures amongst other things are used to introduce and maintain soil organic matter and soil micro-organisms. In many Asian, African and Latin American countries effective micro-organisms are being trialled with promising results (e.g.,Sangakkara & Higa, 2000). Effective micro-organisms are cultured by fermenting rice-based organic material. Other "inoculums" like compost teas and fermented teas (herb, seaweed) can be used in a similar way. Biodynamic preparations are at times included in this list.

Nutrient cycling and energy flows in terrestrial ecosystems are tied to the turnover of organic matter in soil. Although small in mass (we are still talking about tons per acre), the microbial biomass is amongst the most labile pools of organic matter and thus serves as an important and dynamic reservoir of plant nutrients. The succession of the soil microbial population during ecosystems development and soil development shows that a simple food web is vulnerable to external stress and largely based on a limited number of mainly bacterial species that build up a food source (humus; see also Appendix 2) in the soil. Once the humus has reached a certain site specific level, the soil microbial population stabilises into a long-term energy-efficient, harmonious, (semi) closed system and supports a mature or climax ecosystem. The soil food web structure has changed from being relatively simple, vulnerable and bacterial based into a complex, stable community structure, rich in diversity and with an increased fungi population.

The first phase mainly represents growth and production, while the mature phase represents stability and quality (see also Table 1). The mature system has an increased nutrient buffer in the form of higher (soil) organic matter and biomass content and a higher rate of internal recycling, meaning less nutrient losses from the system and more nutrients tied up in the biomass. With higher organic matter contents and complex soil food webs, soil borne pests and diseases are suppressed (van der Werff, 1992; Tugel, 2000).

Soil biota is clearly important for (organic) soil management. It is a key aspect of plant nutrition, of pest and disease suppression, as well as of environmental degradation.

Organic farming is about finding the balance between the juvenile stage (high production, vulnerable to stress/perturbation/disturbance) and the mature stage (stability, quality, efficient). Mainstream farming emphasises the juvenile stage (high production, vulnerable to pests and diseases, more losses from the system).

As a net result, the mature stage has a semi-closed nutrient cycling process, meaning lower losses from the system and increased nutrient sinks/pools.

A clear example is the excessive nitrogen losses from the farming system. The major water contaminant in North America and Europe is nitrate-N, which is also becoming an increasing challenge in New Zealand. The recognised principal sources of N-loss are the conversion of native to arable land use, fertilisers, animal manures and other nitrogen inputs (Soil Biology Primer, 2000; Waldon et al., 1997). Soil management practices are known to influence N leaching. The major factor influencing N-losses are excessive rain or irrigation, mineralisation, immobilisation, nitrification, denitrification and humification (Bloksma, 1996). The net results of these processes generally result in less nitrogen leaching under organic management than under conventional management (Schluter et al., 1996; Stopes & Phillips,1994; Power & Doran, 1984). Although not all research indicates a reduction in N leaching on organic farms, reduction of all losses from the system and thus reduction of N losses is one of the aims of organic farming systems.

In 1993, an international workshop on nitrogen leaching in ecological agriculture (Kristensen et al., 1995) identified key factors and recommended research work aimed at improving and designing organic farming systems. Environmental and soil remediation has become a major (knowledge) industry. The contribution of organic research centres to these challenges of reducing nutrient leaching and water contamination has been recognised. For instance, LBI has been developing a model for nitrogen dynamics for ecological arable farmers called NDICEA (Nitrogen Dynamics In Crop rotations in Ecological Agriculture). Work on the model has increased knowledge of regional and seasonal mineralisation rates and net results of the competing processes of mineralisation, immobilisation and humification (Habets & Oomen, 1993; van der Burgt, 1998; Bokhorst & Oomen, 1998; Oomen, 1995). NDICEA is becoming a promising instrument to assist in farm management and facilitation by researchers. More important, it has created insights into the relevant regional and seasonal soil processes. The model will be exposed to testing under various different (soil) conditions in further research programmes.

Models can be useful but have disadvantages too. Condron et al., (2000) reported on nutrient dynamics using budgetary models developed with mainstream farming research data. They expected that organic farming systems could support themselves with biological nitrogen, but expressed concern about continuing phosphorus availability. Nutrient budgets are a good linear approach but fail to explain what goes on inside the "Black Box", in this case the soil system, and the input-output approach does not explain the internal functioning of the system. We know that the soil under organic soil management is generally different (see soil quality sub-section) from soil under conventional farming systems, which mean that the behaviour of the soil system under organic management is different. As a consequence, the current mainstream working models or budgets might not be appropriate tools for research on organic farming systems.

A paper produced by FiBL (Fliesbach et al., 2000) on nutrient dynamics in biodynamic farming systems concluded:

Waldon et al., (1998) also compared the performance of two very similar soil ecosystems under organic and conventional management. They concluded:

This can partially be explained by the use of organic fertilisers as opposed to inorganic fertilisers. Moritsuka et al., (2001) studied the effects of organic and inorganic fertilisers on the nutrient dynamics in the rhizosphere, and concluded that the contribution of the net supply of N, P, and K through the replenishment from the solid phase was higher for the organic fertiliser treatment than for the inorganic fertiliser treatment. In short, inorganic fertilisers reduce the efficient use of the soil system’s mineral resources.

In the light of these results, the concern of Condron et al., (2000) about continous phosphorus availability under organic soil management might not be warranted. Phosphorus availability is largely determined by mineralisation (by phosphatase enzymes) due to microbial and plant activities (Speir & Ross, 1978). Phosphorus mineralsation rates are correlated to nitrogen mineralisation rates, microbial activity and humus. It is decreased by high phosphate concentrations. Mineralisation rates are also higher in the rhizosphere. Oberson et al., (1993) reported that the soil microbial biomass and the activity of the enzyme acid phosphatase were higher under the organic soil management plot in their long-term field trial. These results were attributed to both the higher quantity of organic carbon and organic phosphorus (organic matter) applied in these systems and also to the absence of or severe reduction in chemical plant protection. A further conclusion drawn was that phosphorus could not be the factor limiting crop yield under organic management. The ability of phosphorus to leave the soil solid phase was significantly higher under the biodynamic treatment than under all other treatments. This was explained by the higher calcium and organic matter contents in this system. Other important factors in increasing phosphorus uptake are the presence of mycorrhizal associations and earthworms, which have been extensively reviewed (e.g., Quarles, 1999; Singh & Aneja, 1999; Lee, 1985; Pankhurst et al., 1994).

The soil system with its components of soil organic matter, soil life community structure and nutrient dynamics plays an essential part in the global water, carbon, nitrogen, phosphorus and sulphur cycles. Soil organic matter (see Appendix 3 for more information) and biomass are a major sink or pool for carbon, nitrogen, phosphorus and sulphur. The turnover, cycling rate and availability are under the influence of soil organisms. According to the Soil Biology Primer (Tugel, 2000) the food web serves the land manager in the following ways:

• fertiliser requirements may decline as a healthy food web efficiently stores and recycles nutrients;
• nitrates do not leach into groundwater when soil organisms hold nitrogen in the rooting zone;
• water quality is protected when organisms effectively degrade pollutants;
• more water soaks into the soil and can be used by crops as biological activity enhances soil structure;
• pesticide use can be reduced as disease suppression improves with a healthy soil food web.

Landscape quality and organic soil management

Landscape quality, directly related to soil quality, is beginning to attract attention overseas but is underexplored in New Zealand. The degradation of the environment (soil, water, air), loss of nature (flora and fauna), and depletion of natural resources go hand in hand with the degradation of landscapes and loss of livelihood in rural communities. Agenda 21, the report of the United Nations Conference on Environment and Development (1992) has further stimulated national and regional authorities to take action, which has led to increased global interest in biodiversity and conservation and in sustainable and ecological development.

Promulgation of the Resource Management Act (1991) showed New Zealand as a front-runner in these developments. There have also been various fragmented efforts to enhance overall environmental quality in New Zealand. In Europe, concern about landscape quality led to the development of the EU Concerted Action group, which encouraged structured scientific research (van Elsen et al., 2000). The EU Concerted Action group developed a checklist for EU sustainable landscape management as a tool for policy making (van Mansfelt et al., 1999). Organic farming is increasingly recognised as being part of that development. As stated by van Mansfelt et al.. (1998):

A database search or organic farming and landscape literature resulted mainly in the recovery of European oriented literature. The available literature on landscape and organic farming systems in New Zealand is limited. A well-designed and managed organic crop rotation has the potential to contribute towards improved sustainable development in the catchments area (or landscape) (van Steensel, 1995).

Organic farming systems have characteristics such as increased biodiversity that enhance the landscape (Braat & Vereijken, 1992):

• 200% to 2000% more beetles and earth worms (this has been confirmed for earth worms in New Zealand by Reganold et al., 1993);
• 50–700% more species of bees, butterflies, bumblebees and spiders;
• 130–700% more herbs and non-crop species as compared to conventional farms (Austria, Germany, The Netherlands, and Switzerland);
• 30–800% more birds reported in Germany, the Netherlands and the USA.

The increased biodiversity of organic farms in Europe includes species from the endangered species list. On these organic or ecological farms there can be an increase in diversity of land use types, including more use of woodlots, linear planting and crops compared with practices on traditional farms. Kuiper, (1997) reported on the diversity of landscape elements, ecosystems and species.

These reports show that organic (including biodynamic) management tends to increase the diversity of fauna and flora considerably. As stated by van Mansfelt et al., (1998), increased biological diversity seems to go together with increased diversities of land use in general, and diversity of labour and spatial structures. This view is supported by agro-ecologists such as Altieri, (1994):

Organic farming systems contribute well to landscape quality and are therefore supported by various governments in Europe. Stroeken et al., (1993) indicated that landscapes deliberately developed on farms (landscape production) can be studied. Regional identity (based on ecological and historical strengths of the region) became an overall goal, encouraged by the Dutch Government, for example, to stimulate local products and tourism.

Soil and landscape develop naturally together into unique diverse units that vary across continents and islands, providing global biodiversity and thus creating the global life support system. A change in flora and fauna communities on top of the soil goes together with a change of community structure in the soil, and will affect nutrient turnover rates (microbial biomass and activity). An increase in biodiversity generally accompanies improved stability in and on top of the soil.

Organic farming systems contribute to this, although there is recognition in Europe of the challenges of increased diversity in the agro-ecosystem. Unless well designed, such diversity could lead to chaotic fragmentation, so research is concentrating on coherence within the farming system as a whole (van Mansfelt et al., 1998). The basic farming concept in biodynamic farming is referred to as managing the farm identity or farm individuality. The appropriateness of nature and landscape development to the organic farm identity has been described by a team from the Louis Bolk Institute (LBI) (Vereijken et al., 1997):

• a method to describe the farm individuality;
• the people who live and work on the farm are part of the farm individuality, so they should participate in the (research) planning process; and
• landscape is perceived as a dynamic system and individuality is also a dynamic concept.

The LBI team (1997) presented a method designed for landscape-development planning at farm level, based on the concept of farm individuality and a Goethean-phenomenological approach. The method, which involves a participatory on-farm research methodology, can be characterized as a bottom-up rather than a top-down approach. It enables farmers to coooperate in landscape planning with all their ideas, feelings and future plans for their farm. The method is illustrated in work recently carried out on a Dutch organic farm, the ‘Noorderhoeve’ (Baars & van Gelder, 1994).

Biodiversity and farming

Biodiversity is an important aspect of the relatively new discipline of ecology, which plays a major role in sustainable development. Involving more than the problem of loss of species that appears to be the common concern, biodiversity refers to all species of plants, animals and micro-organisms that exist and interact within an ecosystem (Vandermeer & Perfecto, 1995). When species are lost, so are certain functions and developments up and down the hierarchical scale. In natural ecosystems, the vegetation cover of a forest or grassland prevents soil erosion, replenishes groundwater and controls flooding by enhancing infiltration and reducing water runoff (Perry, 1994). There is interaction between the soil and the rest of the ecosystem. As defined by Altieri, (1999):

These are mainly ecological processes and to maintain them a certain level of functional biodiversity is required. From an economic point of view, this means that if an agricultural system is deprived of basic regulating functional components, resulting in loss of soil fertility and pest and disease regulation, there is an increasing need for costly external inputs. Swift and Anderson (1993) stated:

This means that enhancing biodiversity in agro-ecosystems is a key strategy to bring sustainability to production. This involves a shift towards mature or climax characteristics, a move away from an over-emphasis on production (developmental phase) towards more quality and internal regulation (mature phase) (Table 1).

Agro-ecological-based farming systems like organic farming should include strategies that exploit the complementarities and synergies resulting from various combinations of crops, trees and animals (in space or time). These include arrangements such as poly-cultures, agro-forestry systems and crop-livestock mixtures (Reijntjes et al., 1992). Insect pest problems are increasingly linked to the expansion of mono-cropping and the loss of landscape diversity or local habitat diversity (Altiery & Letourneau, 1982, 1984; Andow, 1991). Odum, (1996) concluded that with the maturing of a system the biodiversity increases, which is accompanied by a reduction in insect pests, increased stability, less losses from the system, and so on.

Soil-plant-animal health and organic soil management

The view that plant health, animal health and human health are related to soil conditions has been promoted by many scientists with a strong academic background, such as Steiner, Howard, Balfour, Muller and Rusch, Boucher, Pfeiffer, Albrecht, Voisin, Hamaker and later Chaboussou. The link between plant health and soil conditions is becoming increasingly obvious in modern research. Chaboussou’s (1987) work leads him to the following statement: "Healthy plants do not get sick".

Disease suppression in plants as a function of the soil (life) has been discussed at various conferences (e.g., IFOAM, 1992/94/96/98; Ingham, 1999/2000; Pankhurst et al., 1994).

Chabossou, (1977 & 1985) indicates that metabolic disturbance in plants caused by pesticides influences or unbalanced crop nutrition influences plant health negatively.

Trace-elements and other mineral balances in the soil are also becoming increasingly recognised as having an influence on plants (Bloksma, 1996; Andersen, 1989) and animal health. Condron et al., (2000) stated "Trace element deficiencies occur in the human population in New Zealand as well as in livestock". Furthermore, Condron et al., recognised the potential of organic farming systems to produce plant and animal products appropriate for the human diet. Voisin (1959) stated:

Conclusions

A UNDP publication (Benefits of Diversity, 1992, p.4) on sustainable farming states: "In reality organic agriculture is a consistent systems approach based on the perception that tomorrow’s ecology is more important than today’s economy".

This report advocates readjustment by economy to primary production factors and not the other way around. Without ecology, there is no economy. If conventional agriculture had been made to pay for the degradation and environmental damage it caused, the move towards ecological and organic farming systems would have been made long ago. The aim is to stop degradation and re-establish natural balances. In Europe, research emphasis has shifted from the validation of the organic farming system to finding practical solutions for theoretical and especially practical challenges. In organic farming there is a different, organised ‘practice’ with its own ethos, which ought to have consequences for scientific research (Baars, 2000). An ecological or organic scientific platform could close the gap between ‘grass roots’ organic organisations and policymakers and other research institutions. The dependence of organic farms on biological activity (for instance, to supply nutrients to plants) requires a different methodical systems approach in which a mutual transfer of knowledge between farmer and scientist is valued.

Yield and production are seen in the local literature as limiting factors for the development of New Zealand organic farming. There is a different emphasis in organic farming systems, an emphasis on quality rather than quantity, on optimum production rather then on maximum production. However, both can be significantly improved (quantity and quality) if the same amount of research funding was allocated to researching organic farming systems as to mainstream farming systems. IPM strategies (a strategy between conventional and organic farming), for example, receive more funding than organic farming systems. These strategies, however, involve the first two steps towards sustainability: improving efficiency of existing systems and input substitutions. The third step is generally not taken outside the organic sector: a conscious re-design of the agro-ecosystem (Hill, 1990). This step requires knowledge and understanding of those agro-ecosystems.

In Europe, dedicated organic or ecological research centres have gathered this knowledge and understanding and are defining and researching the conscious re-design of agro-ecosystems in conjunction with farmers. In New Zealand such understanding is mainly held by a few experienced organic farmers and scientists. For scientists to help more farmers adopt truly sustainable organic farming systems, wider understanding of and research into soil ecological processes is required.

Recommendations

• More research on soil food web and biological processes is required for organic soil management, as well as for general sustainable farming methods. Processes such as immobilisation, mineralisation and humification are therefore important for study. More important is the net result of these processes in the soil. Regional and seasonal mineralisation rates and related processes in New Zealand soils should be inventoried.

• To sustain system maintenance, basic soil quality indicators need to be determined and used to monitor soil management effects and identify soil management problems through an understanding of the soil’s functions and development.

• A participatory on-farm research methodology based on phenomenology should be adopted.

• Strategies for enhancing of biodiversity in agro-ecosystems should be investigated. Such strategies are a key sustainability and a move from an over-emphasis of production towards more quality and internal regulation.

‘Specialised’ research centres are needed to direct and manage a holistic and ecological approach to organic soil management and build the necessary research skills and experience.

References

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© 2002 Bio Dynamic Farming and Gardening Association in NZ Inc.