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EAP Publication - 108

Farm-scale Agronomic and Economic Conversion from Conventional to Sustainable Agriculture

Rod J. MacRae, Stuart B. Hill, Guy R. Mehuys and John Henning


I. Introduction
II. Attitudes Towards Conversion and Rationale
III. Length of the Conversion Period
IV. Key Elements in Developing an Action Plan

A. Farm Inventory and Needs Assessment

B. Soil Improvement
1. Organic Matter Management
2. Supplemental Fertilization
3. Manure and Slurry Management
4. Crop Rotation
5. Appropriate Tillage
C. Agronomic Changes
1. Stocking Rate Adjustments
2. Weed, Insect and Disease Control
D. Economic considerations
1. Marketing Possibilities
2. Labour Requirements
3. Yield Projections and Financial Planning

V. Conversion Without Animals

VI. Implications of Widespread Conversion

VII. Conclusion



I. Introduction

Sustainable agriculture is receiving increasing attention in North America and Europe because of four main factors: increasing concern about degradation of the agricultural resource base, low commodity prices that have sent many producers looking for low-input alternatives to cut costs, consumer concern for food quality, and a perception that the quality of rural life is deteriorating.

Up to now much of the burden of creating a sustainable agricultural system has rested on individual producers. Many have considered the task daunting, feeling that there is insufficient information and institutional supports available to ensure success. Surveys of farmers using sustainable practices have identified lack of useful information from agricultural institutions and government as a major impediment to conversion (Blobaum, 1983; Hill, 1984a; Kramer, 1984; Robinson, 1985, 1986). The knowledge gained by those who have successfully converted is now being supplemented with information generated from sustainable agriculture research. This paper focuses on this emerging body of information.

Most authors have described sustainable agriculture either in negative terms (no or minimal dependence on synthetic fertilizers, pesticides, and antibiotics) or in terms of substitute practices (use of manure, crop rotation, minimal tillage) (e.g., USDA, 1980). Because such descriptions neglect attitudes, goals, and values and the redesign component of sustainable agriculture, we have provided the following, more comprehensive definition.

Sustainable agriculture is a philosophy and system of farming. It has its roots in a set of values that reflects a state of empowerment, of awareness of ecological and social realities, and of one's ability to take effective action. It involves design and management procedures that work with natural processes to conserve all resources, promote agroecosystem resilience and self-regulation, minimize waste and environmental impact, while maintaining or improving farm profitability.

Of particular importance is working with natural soil processes. Sustainable agriculture systems are designed to use existing soil nutrient and water cycles, and naturally occurring energy flows for food production. As well, such systems aim to produce food that is nutritious and without products that harm human health.

In practice such systems have tended to avoid the use of synthetically compounded fertilizers, pesticides, growth regulators, and livestock feed additives, instead relying upon crop rotations, crop residues, animal manure, legumes, green manure, off-farm organic wastes, mechanical cultivation, and mineral-bearing rocks to maintain soil fertility and productivity, and on natural, biological and cultural controls to control insects, weeds, and other pests.

Within such a definition a great number of approaches and philosophies is possible, and the particular strategies for conversion will depend as much on the attitude of the farmer as on the availability of scientific, technological, economic, and institutional supports. A number of sustainable agriculture philosophies have evolved and each school of thought has produced its own literature on conversion, creating some confusion for farmers and scientists interested in the process. To clarify this, we employ Hill's (1985) evolutionary approach to the conversion process that has three components:

1. Increased efficiency -- conventional systems are altered to reduce consumption of costly and scarce resources, e.g., by banding fertilizers, monitoring pests, optimal crop siting, and timing of operations.

2. Substitution -- resource-dependent and environmentally impacting products and practices are replaced by those that are more environmentally benign, e.g., synthetic nitrogen fertilizers by organic sources, pesticides by biological control agents, moldboard plows by chisels or discs.

3. Redesign -- causes of problems are recognized, and thereby prevented, and solved internally by site and time-specific design and management approaches instead of by the application of external inputs, e.g., the farm is made more ecologically and economically diverse and therefore also more resource self-reliant.

The main alternative agricultural philosophies are categorized according to these three components in Table 1. Our assumption is that there are advantages to the farmer in following an efficiency/substitution/redesign progression in the transition to sustainable farming practices. Although a permaculture or natural approach, by which one relies for food on the productivity of "permanent" structures such as trees, perennial species, or other undisturbed plant/soil systems, is perceived by some to be the ultimate goal of a sustainable farming system, the path to its achievement is quite long and difficult given our present level of understanding of agroecological systems (Mollison, 1979; Fukuoka, 1985). Our focus here will be on research that addresses conversion to the early stages of redesign, emphasizing methods that are relatively easy to implement and that minimize financial risk.

Approximately 4000 farmers have converted to sustainable practices in Canada (Hill, 1989), at least 30,000 in the USA (Harwood, 1983), several thousand more in Europe (Peter and Ghesquiere, 1988) and many more are in the transition phase. These farmers are testimony to the agronomic and economic feasibility of sustainable farming systems, and a number of investigators have studied their success (Oelhaf, 1978; Lockeretz et al., 1981; Vogtmann, 1984; Lampkin, 1985a, 1986; Cacek and Langner, 1986; Lockeretz and Madden, 1987 - see section IV.D.). This review is based on the experiences of and experimentation by farmers, and results of scientific research.

II. Attitudes Towards Conversion and Rationale

Why do farmers convert and how are they affected by the conversion process? Until recently, the prime motivation has been fears about environmental degradation (particularly of soil and water) and deteriorating human health, often of someone within the immediate family (Blobaum, 1983; Hill, 1984a; Robinson, 1985; Bateman and Lampkin, 1986). Now, however, the depressed economic situation is making more and more farmers look to alternative farming practices as a way to cut input costs and maintain or recover financial health. Although yields may be lower in sustainable agriculture systems, almost all investigators and surveys (with the notable exception of Vine and Bateman [1981], whose study was limited to a single year of observation) report that total costs are substantially lower and that net incomes are at least as high or exceed those of conventional farmers, particularly for organic farmers for whom premium prices may be available (see section IV.D).

One common, although not prerequisite, motivational change among farmers in transition concerns the way they view the farm and the practice of farming. Many experience a major shift in their values and place even greater emphasis than before the transition on their role as guardians of human health, through the provision of essential nutrients to consumers, and of the health of the rural community and environment. Hill (1987) considers that the attraction to the different methods of farming is determined by past and present environmental influences. The traumas experienced as children that make us feel inadequate and powerless are particularly significant in this respect because they may create attractions to high-technology approaches to agriculture. According to Hill, these attractions are confronted, consciously or unconsciously, directly or indirectly, explicitly or implicitly, by many farmers as they change their farming practices.

Another common change is that farmers become more aware of the "organismal" nature of the farm, which functions well when all its components are present and when essential biological processes are supported through the careful management of events in time and space (Koepf et al., 1976). Because of the uniqueness of each situation and because of the changing nature of environments, there can be no reliable formulae for successful transition. Farmers must aspire to be sufficiently competent to respond appropriately to their own unique set of changing conditions.

Many farmers have found converting to be an unsupported, isolating, and stressful experience. Relevant government support is usually lacking (Oelhaf, 1978; Lampkin, 1985b) and ridicule by neighbors is common. Because farmers have had difficulties obtaining relevant information from conventional sources, they have tended to rely on other farmers (at field days, conferences), salespeople for alternative products, on-farm experiments, popular organic-farming magazines, and classic, largely European, literature from several decades past (Hanley, 1980; Blobaum, 1983; Kramer, 1984; Robinson, 1985; Baker and Smith, 1987). These classics include scholarly works by Howard (1943, 1947) and Albrecht (1975) and more popular discussions by Steiner (1924), Bromfield (1947), Sykes (1949), Hainsworth (1954), Turner (1955), Voisin (1960), and Balfour (1975).

Many converting farmers come to regard conversion as an on-going process that requires a high level of commitment (Robinson, 1985; Blake, 1987). Those who do not take this view are more likely to give up or experience difficulties (Plakholm, 1985; Lockeretz and Madden, 1987). The articulation of clear goals, both for themselves and their farms, and the development of plans for their achievement are prerequisites for success (Hanley, 1980; Brusko et al., 1985; Hart, 1989). Such plans may include a period of reduced profits during the conversion period, when attention is focussed on ensuring financial liquidity, flexibility, and evolution of the new systems of production (Côté, 1986).

III. Length of the Conversion Period

The conversion process usually takes from three to six years. One proposed explanation for this is that the toxic residues associated with conventional methods of production may prevent certain biological processes from reaching a new, necessary equilibrium (DeBach, 1974). Decomposers of organic matter in soil and natural controls of pests may be affected in this way and this can translate into yield and income losses for up to six years (USDA, 1980; Dabbert and Madden, 1986). In many cases, however, yields recover in two to three years (Oelhaf, 1978; Brusko et al., 1985). Because of the financial implications of any yield reductions, it is generally advisable to start by converting a small part of the farm, perhaps 10% (Brusko et al., 1985; Wookey, 1987), although some recommend up to one-third (Preuschen, 1985). Farm structure and soil fertility often determine the speed and area of transition. Pastures that have received little or no synthetic fertilizers and pesticides can be converted quickly (Aubert, 1973; Preuschen, 1985), especially when part of a beef operation (Pousset, 1981). Whole-farm conversion is advocated by some because the effects of alternative strategies are easier to see in the absence of conventional inputs and practices (Manley, 1988). Although such approaches have been successful, they are usually also traumatic and may, in fact, lengthen the conversion period because of unanticipated effects (Patriquin et al., 1987).

Successful conversion usually requires that farmers become researchers and that their farms become experimental farms (Koepf et al., 1976; Hanley, 1980; Peters, 1987). Several publications have been written to support them in this task (McLarney, 1973; Pettygrove, 1976; Levitan, 1980; Brusko et al., 1985; Hergert, 1986).

IV. Key Elements in Developing an Action Plan

Aubert (1982) has warned against the common tendency to adopt automatically what has been successful elsewhere, thereby ignoring the unique features and situation of each farm. Many Canadian producers have learned by experience that practices used in Europe or in the USA are not directly transferable to their conditions (Robinson, 1985).

Producers wishing to convert will benefit by developing a detailed plan that includes at least the following elements and is specific to their situation and needs: soil improvement measures; manure or slurry handling methods; development of a crop rotation; fertilizer/manure applications; tillage alterations; livestock stocking-rate adjustments, if animals are involved; weed, pest, and disease control techniques; mechanization, housing, and storage requirements; marketing opportunities; labour requirement estimates; yield estimates; financial estimates and implications; and a timetable for conversion (Lampkin, 1985b; Plakholm, 1985). Research results concerning ten critical aspects of any conversion plan are discussed below.

A. Farm Inventory and Needs Assessment

Because sustainable agriculture is designed to maximize the use of the farm's internal resources and minimize the purchase of off-farm inputs, a farm inventory, covering available physical, biological, and human resources, is a critical first step in the conversion process (Table 2). The inventory serves to identify losses and inefficiencies in the farm system that can be reduced, and inputs that can be eliminated in the initial stages of conversion.

The soil inventory should include evaluations of soil organic matter and trace minerals (Aubert, 1973; Hanley, 1980). Organic-matter quality, expressed as degree of humification, should be recorded (Brinton, 1983), as should the biological activity of the soil (Aubert, 1974; Deavin, 1978; Bourgignon, 1989). Such measures may not provide direct answers to questions about soil conditions, but can contribute to an overall appreciation of the state of the soil ecosystem. Availability and quality of organic fertilizers, such as manure, crop biomass, and green manure, should also be assessed (Koepf et al., 1976). To ensure that trace mineral uptake by plants is not inhibited, an optimal balance between the major cations should be achieved. Albrecht (1975) regards 65-75% Ca++, 10% Mg++, 2.5-5% K+, and 10-20% H+ as optimal. Aubert (1973) suggested that if the farm's history is not well known, the soil should be tested for residual pesticides, although these tests are usually expensive and few labs can perform them.

The biotic inventory should include crop histories; predominant weed species; forest, bushland, and shelter belt resources; prominent pest and beneficial insects; non-insect pests; and wildlife. Pests should be seen as indicators, or symptoms, of fundamental problems in the design and management of the farm, rather than as enemies to be controlled and eliminated (Hill, 1985). Weeds often indicate soil conditions because their presence indicates that an environment favourable to their growth habits has been created (Cocannouer, 1964; Hill and Ramsay, 1977; Walters and Fenzau, 1979; Hanley, 1980; Kourik, 1986). The presence of chickweed, for example, may indicate incomplete breakdown of organic matter in soil (Walters and Fenzau, 1979). Tissue analyses of weeds and crops can also provide useful information on soil conditions. Similarly, insect pests and diseases may indicate an imbalance between the organisms and their natural controls (Hill, 1984b; Altieri, 1987), or deficiencies and excesses of nutritional elements in the plant (Robinson and Hodges, 1977; Patriquin et al., 1988; Eigenbrode and Pimentel, 1988). Noting and responding to such indicators may require more analytical skills and time than in conventional production systems, but the benefits can be substantial, as when permanent solutions to problems are found.

Availability of water is also an essential element of a farm inventory (Yeomans, 1978). Although many producers following sustainable approaches do invest in drainage and irrigation equipment, some avoid the associated costs by designing their cropping systems to make optimal use of the natural moisture conditions. For example, in a poorly drained clay soil, a farmer might substitute tolerant crops, such as oats for wheat and red clover for alfalfa, rather than install expensive subsurface drains. The aim is to intervene benignly in the water cycle, maximizing efficient use while minimizing environmental disruption and pollution. The feed quality or market potential of replacement crops should also be assessed as many have not achieved the popularity of those they replace (Hanley, 1980; Francis et al., 1986).

Once these basic inventories have been completed, an assessment of input needs can begin. Although farmers have traditionally had little control over input and product prices, they can control input costs. This is particularly important because the productivity of inputs is declining (Cox, 1984; Myers, 1988). The pros and cons of all purchased inputs should be assessed carefully. For example, although hybrid seed has many advantages, it cannot be saved and planted the following year. Some low-input and organic farmers prefer non-hybrid varieties that they can save, although it may take two to three generations of seed production before the desired quality is achieved (Balfour, 1976). Another problem is that most commercially available seed has been selected in highly controlled, N,P,K-rich, pest- and weed-free environments. Because such conditions differ from those on sustainable farms, many producers have found older, traditional crop varieties to be better suited to their production or marketing needs (Buchting et al., 1986; Patriquin et al., 1987; Frost, 1989), although empirical studies to test this contention have not show this to be clearly the case (Dixon and Holmes, 1987). Unfortunately, many of these varieties are no longer commercially available. Because varietal development for "minor" crops has been historically weak (Buttel, 1987), in the short term, farmers are unlikely to receive much assistance in the genetic improvement of traditional varieties, nor even for modification of recently developed lines (Dixon and Holmes, 1987).

Machinery and building needs must also be examined. As farmers diversify and as the tilth of their soil improves, many find that they can retire some large, or high-horsepower machinery. In the U.K. many organic growers have reduced tractor horsepower from 90-100 down to 70-80 horsepower (Patterson and Bufton, 1986). Equipment needs are often met with second-hand equipment and the retooling of equipment already on hand (Kramer, 1984; Brusko et al., 1985), or by establishing or joining a machinery cooperative (Preuschen, 1985; Best, 1986). Retooling is often necessary because appropriate equipment is not yet commercially available (Teichert and Schulz, 1987). Common purchases are chisel plows, cultivators, rotary hoes, and haying equipment (Brusko et al., 1985). Building needs may also be reduced as housed animals are transferred to more open systems of management (Sarvas, 1981; Robinson, 1985). Some transitional farmers, however, do invest in additional buildings and equipment to permit them to process some of their produce (e.g., cheese-making or milling). This allows them to reap "value-added" financial benefits (Hanley, 1980; Goff, 1983; Buchner, 1986) and ensure the quality standards of their produce beyond the farm gate (Rocky Mountain Institute, 1987).

The value of employing consultants during the planning and implementation stages, if knowledgeable ones are available, should be assessed as they may help reduce the conversion time by one to two years (Blake, 1987).

B. Soil Improvement

1. Organic Matter Management

Soil improvement strategies used in the conversion process emphasize organic matter conservation and supplementation. Soil fertility and high-quality organic matter are seen by sustainable producers as almost synonymous, so a variety of techniques for incorporating organic matter into the soil is usually included in the conversion plan, such as addition of animal manure, green manure, and compost, and the use of pastures in rotation. Using a diverse range of organic materials to improve organic matter quality is an important part of the strategy, as is assuring that a range of stages of decomposition is present. Work on organic matter composition indicates that different types of compounds play different roles in the soil (Allison, 1973; Schnitzer and Khan, 1978).

An important, and often difficult, decision is when in the rotation to apply organic matter if supplies are limited. Although this must usually be determined by experimentation (Brusko et al., 1985; Patriquin et al., 1987), likely targets are the first crop in the conversion, high nutrient-demanding crops, and even green manure crops if they are grown in soils low in organic matter (Blake, 1987). Aubert (1973) cautions against heavy applications of animal manure (>50 t/ha) at the beginning of the conversion because the biological activity in the soil may be inadequate for the timely breakdown of the organic material, and the resultant phytotoxins may inhibit subsequent crop growth.

2. Supplemental fertilization

Supplemental fertilization may be required in the early years of conversion, before equilibrium nutrient cycles have been established. Developing appropriate fertilization strategies is especially challenging for those wishing to convert to organic production. In these systems, highly soluble or synthetic fertilizers generally are avoided because many have an acidifying effect on the soil and negative effects on many beneficial soil organisms (Madge, 1981; Arden-Clarke and Hodges, 1988). Parnes (1986) has summarized the nutrient contents of less disruptive macro- and micronutrient sources (Table 3) and appropriate methods for their application. Most organic producers pay special attention to N (section IV.B.3) and K. Some investigators claim that because organic farming systems draw on soil K reserves (Table 4), special efforts must be made to minimize K export from the farm (e.g., sales of hay, straw, and other plant and animal products) or supplementary K should be added (Lockeretz et al., 1981; Culik et al., 1983; Patriquin et al., 1987). Potassium export is not such a great problem for farms that export principally animal products, such as milk and eggs, as compared to cereal producers (Pousset, 1981; Clark, 1987), especially those selling more than 25% of the total crop production (Zettel, 1988). Some farmers maintain their K levels by importing it in animal feed and straw (Vogtmann et al., 1986a). Phosphorus is not usually a limiting nutrient in organic farming except in highly calcareous soils and sometimes early in the growing season when the soil is cool (Parnes, 1986). In these conditions increasing the level of biological activity in the soil appears to be a more viable solution than supplemental P fertilization. Using ridge tillage techniques (Schriefer, 1984) and windbreaks (Soltner, 1976) to help the soil warm up more quickly in the spring may increase biological activity early in the season.

3. Manure and slurry management

Because organic matter is so valued, developing manure and slurry handling systems that minimize losses is essential. These losses can occur during storage, handling, application, and in the soil ecosystem. Although some producers have eliminated manure handling by keeping their animals in pastures, most farmers still house their livestock for part of the year and therefore require a manure collection and distribution system.

The application of raw manure to soil is usually avoided to minimize nutrient losses and negative impacts on plants, soils, and waterways. Raw wastes may produce offensive odors, contain disease organisms, parasites, and weed seeds, lose much of their nitrogen (some of which becomes a pollutant in the air and water), burn young plants, and, during the transition period, may contain pesticides and antibiotics that the farm operator wishes to avoid (Gray et al., 1973; Vogtmann and Besson, 1978; Besson, 1982). Most organic farmers avoid these problems by using solid and liquid digesting and composting systems. Fresh manure may be used when readily available nutrients are required, although this practice may contribute little to the bank of relatively stable soil organic matter (Ott, 1986; Vogtmann et al., 1986a). Guidelines for optimal use of fresh and composted manure are summarized by Ott (1986) in Table 5.

Techniques for solid and liquid digestion of manure have been reviewed by Besson (1982) and Watson (1983) and for farm-scale composting by Koepf et al. (1976), Puetz (1979), Hanley (1980), and Sims (1982). Four points should be stressed during the transition:

1. Conservation of liquid fractions in animal wastes is essential because they contain about half of the N, most of the K, and some mobile trace elements (Watson, 1983; Vogtmann et al., 1986a). Steps should be taken to avoid nutrient losses by runoff or volatilization. By composting on concrete, any liquid that seeps out can be collected.

2. Costs can be minimized by adapting existing equipment. For example, manure spreaders can be modified to prepare compost in windrows by changing the wings on the back of the spreader or by employing a detachable hood (Puetz, 1979; Sims, 1982). Unfortunately, much slurry technology remains expensive (Vogtmann et al., 1986a). Besson (1982) has described some basic approaches to manure digestion that keep costs low.

3. Local sources of suitable organic wastes should be investigated for use during the transition period. Food-processing wastes are usually high in plant nutrient value (Knorr, 1983; Poincelot, 1986), and some communities are successfully developing community composting systems (Golob, 1986; Vogtmann et al., 1986b) from which farmers can collect organic material. Care should be taken, however, to ensure that such materials do not contain unacceptable levels of toxic materials, such as pesticides or heavy metals.

4. Because composting reduces the bulk of the organic material, spreading costs will be lower than for fresh manure (Hanley, 1980). Furthermore, because most of the nutrients are immobilized in compost, it can be spread in the fall with minimal loss of nutrients, whereas fresh manure must usually be spread in the spring (Vogtmann et al., 1986a), unless it is incorporated with a green manure or surface composted.

4. Crop Rotation

The selection of optimal crop rotations is central to successful sustainable farming and is the key determining factor for soil management, weed, pest, and disease control, animal feeding, and ultimately finances (Lampkin, 1985b). There may be biological adjustments as the crop rotation is established and as new crops and biological processes exert an influence on each other. As well, new crops may not have the market appeal of those that were grown in conventional production, so financial adjustments may be necessary. The adjustments will be minimal if the farm has been practicing rotation for some time (Aubert, 1973; Dabbert and Madden, 1986).

Legumes are essential in any rotation and should comprise 30-50% of the cropland (Parr et al., 1983). They can be used as forage (clovers, vetch, trefoil, and alfalfa), as seed to be sold (clovers and alfalfa), as animal feed (faba beans), or as human food (peas and beans). Seed legumes should be avoided between other essential marketable crops, however, because they favour development of weeds (Schmid, 1978). Pasture should also be added, its composition depending on its purpose. If it is for animal feed, it should contain a wide variety of species (grasses and legumes) to be nutritious and palatable to animals (Aubert, 1973; Rodet, 1979; Murphy et al., 1986). Pasture renovation costs can be minimized by using a rotational grazing system (Murphy et al., 1986). Well managed pastures support a diverse plant population, but under conventional grazing certain species are suppressed. Animals select the most palatable species, leaving other plants to dominate the pasture. The rotational system moves animals through small paddocks at a rate that forces the animals to eat all the plants. The result is that one plant species is not favoured over another. Cheap, portable electric fencing systems can be used to minimize costs of managing temporary paddocks (Zahradnik, 1983; Murphy et al., 1986). If the pasture is being used to control weeds, then its composition should be less diverse. Pure stands of alfalfa, rye, and buckwheat are often used to choke out persistent annual weeds (Hanley, 1980). Green manure can be used in rotations for erosion and weed control, and to improve soil physical properties (MacRae and Mehuys, 1985; Vogtmann et al., 1986a).

The best crops to start a conversion appear to be pasture, a hay crop, or annual legume (Aubert, 1973; Pousset, 1981; Blake, 1987; Peters, 1987), although with the present economic situation in North America, a small grain or soybean crop may be the best compromise between biological and economic needs (Dabbert and Madden, 1986; Peters, 1987). Wookey (1987) achieved both objectives. He started his conversion with a spring barley undersown with a clover/grass mixture that became a pasture following barley harvest. Early in the conversion, maize (Aubert, 1973; Brusko et al., 1985; Vogtmann et al., 1986a) should be avoided because it is too nutrient-demanding and delays soil improvement. Sugar beets are often eliminated entirely for the same reasons (Aubert, 1982; Lampkin, 1985a; Buchner, 1986), although some have suggested that sugar beets be left in the rotation at the beginning in order to help finance the conversion period (Zerger, 1984). Vogtmann et al. (1986a) provide rules for designing an effective conversion rotation (Table 6) and for selecting rotation crops in relation to preceding crops (Table 7). They recommend that legumes, pasture, and root crops precede grains.

The availability of nitrogen is critical at the beginning of the conversion. Lampkin (1985b) provides an example of a rotation N budget developed as part of a conversion plan (Table 8). The negative N balance is not a problem in this example because the manure from the livestock that graze on the pasture (Years 1 and 2) and feed on the grains (Years 3 and 4) is returned to the soil. The spring beans (Year 5) must be fed to the livestock, however, to ensure a proper N balance. Patriquin et al. (1987) came to the same conclusion in their studies of a converting farm that used faba beans as a feed source for chickens. In their study the crop rotation alone could not sustain adequate N levels because most of the N fixed by the faba beans was fed to the chickens (Figure 1). Farmers should expect to make adjustments to their rotation for a number of years to balance all the functions that the rotation serves (Brusko et al., 1985; Patriquin et al., 1987).

It is common, however, for farmers to be so concerned with N that they inadvertently apply it in excess in the form of manure or other "organic" inputs. Excessive N, regardless of source, is likely to suppress biological activity (including mycorrhizae and possibly associated P uptake by plants [cf. Mosse, 1986]), reduce nodulation in legumes, give a competitive advantage to the weeds over the crop, and increase pest incidence (Chaboussou, 1982; Coleman and Ridgeway, 1983; Patriquin et al., 1987, 1988; Patriquin, 1988a,b).

5. Appropriate Tillage

Most converting farmers alter their tillage practices to reduce soil degradation and losses by erosion, improve weed control, and produce more timely organic-matter decomposition and especially improve soil fertility. The approaches used (Table 9) depend on the farmer's knowledge, access to equipment, and on the farm's particular economic and environmental conditions (Schriefer, 1984; Brusko et al., 1985).

A common aim is to provide optimal conditions for beneficial soil organisms, thereby enhancing organic-matter decomposition and nutrient cycling. Managing the top 8 cm of soil is vital because most of the biological activity, microorganisms, and organic matter is found in this soil layer (Hill, 1984c; Preuschen, 1985; Kourik, 1986). As a result, most producers using sustainable farming techniques rarely use moldboard plows, favoring instead chisels, discs, and harrows which mix the soil in the top 25 cm rather than invert it (Parr et al., 1983; Schriefer, 1984; Brusko et al., 1985). Chisel plowing has limited application, however, in areas with moist fall conditions, such as Eastern Canada (Lobb, 1986). Another popular technique is to create ridges after primary tillage in the fall. Ridges help warm up the soil in the spring and encourage decomposition of crop residues and any green manure incorporated the previous fall (Schriefer, 1984). Some producers will plant on the ridges if the soil is particularly wet (Schriefer, 1984; Moore, 1986; Little, 1987). Patriquin et al. (1987) found that ridging, by improving aeration, helped solve chronic organic-matter decomposition problems and increased yields.

In some cases, compacted soil must be loosened by using deep chisel tillage or a subsoiler. Alternatively, a deep rooted green manure crop such as alfalfa or sweet clover may be helpful in breaking up hardpans (Hanley, 1980; Lampkin, 1985b). However, because alfalfa has a high K demand it must be managed to prevent K deficiency in subsequent crops (Vogtmann et al., 1986a). Tillage alterations may add to total tillage expenses if more passes over fields or specific equipment are required (Enniss, 1985; Lampkin, 1986).

C. Agronomic Changes

1. Stocking Rate Adjustments

In operations with livestock, stocking rates are adjusted to balance feed self-sufficiency and nutrient cycling. In Europe, stocking rates of 1.0-1.2 Livestock Units (LU)/ha are recommended (Koepf et al., 1976; Lampkin, 1985b; Plakholm, 1985), or roughly 80% of conventional rates (Vine and Bateman, 1981). On small farms, because farmers often focus on higher-value crop products, even lower stocking rates are common (Blake, 1987). Stocking rates are likely to be lower on North American organic farms (Brusko et al., 1985; Robinson, 1985), especially on range land where rates of 0.1 LU/ha are common (Jackson, 1987), although rates similar to those in Europe have been recommended in Saskatchewan (Hanley, 1980). Recent work, however, on rotational-style grazing systems, which divide pastures into smaller areas and rotate animals through them quickly to facilitate the pasture's rapid recovery from grazing, suggests that stocking rates can be considerably higher (Savory, 1985; Murphy et al., 1986; Murphy, 1987). Stocking rates for hens are recommended not to exceed 120 hens/ha, depending on the type of operation (i.e., deep-litter floor, aviary, or free range) (Fölsch, 1986).

Because farms often diversify during the conversion period, ending up with more than one livestock operation, the total number of animals is often higher than on conventional farms, even though stocking rates per animal species may be lower (Brusko et al., 1985; Robinson, 1985). Livestock operations can be designed to be complementary. For example, adding a dairy-goat operation to an existing cow herd may provide new market opportunities and the goats will eat weeds and pasture grasses that cows may reject (Considine, 1979). Sheep may be added to a dairy-cow operation at a 1:1 ratio without requiring any additional grazing area (Blake, 1987). The costs and benefits of multispecies grazing have been discussed in a volume edited by Baker and Jones (1985).

When adding livestock to complement a cash cropping operation, labour-saving animal operations are desirable. For example, a beef finishing or sheep breeding and finishing operation require less investment and labour than a beef or dairy cattle breeding operation (Pousset, 1981; Boggs and Young, 1987). Finding complementary livestock operations for ornamentals and fruit production has been less successful, although integrating ground-feeding birds, such as poultry and geese, with fruit trees appears promising for weed and insect control (Lafleur and Hill, 1987).

2. Weed, Insect and Disease Control

Some of the most interesting solutions to plant and animal protection problems have been developed by organic farmers who rarely use synthetic chemicals. Except in fruit and possibly potato production, organic farmers do not usually have major problems with insects and plant diseases, probably because plant and insect diversity within the redesigned agroecosystem is greater (USDA, 1980; Kramer, 1984; Altieri, 1987). Certain pest problems that do arise are usually traceable to inappropriate rotations. For example, rotations designed with too many years of legumes help perennial weeds to spread, and excessive use of cruciferous green manure encourages certain insect pests (Lampkin, 1985b).

In addition to fewer plant pest problems, the incidence of livestock disease (and associated high veterinary bills) is much lower than in conventional production (Kramer, 1984; Brusko et al., 1985; Plakholm, 1985; Robinson, 1985). The reasons include higher feed quality, lower stocking rates, and reduced stress on the animals. These results can be achieved by: 1) eliminating pesticide residues from the diet; 2) increasing forage and reducing concentrate in the diet, e.g., for cattle, less than 5 kg/animal per day concentrates and more than 20% fibre is advised to prevent rumen acidosis; 3) altering building design, e.g., stress to pig's feet is reduced by removing slatted floors; 4) ensuring adequate straw bedding; 5) better management of colostrum (immediate suckling of newborn and use of older cows, which generally have better colostrum, for breeding); and 6) changing to traditional breeds that have not been bred for intensive production systems that rely on high levels of external inputs (Boehncke, 1983, 1985, 1988; Kiley-Worthington, 1986; Vogtmann et al., 1986a; Clark and Christie, 1988). Some organic farmers substitute homeopathic and herbal remedies for conventional curative measures (Quiquandon, 1982; Schofield, 1984).

Of the three categories of pests, weeds pose the main problem to most converting farmers. Weeds are generally controlled by rotation, tillage, mowing and occasionally handweeding, or letting livestock (e.g., pigs and geese) loose in the fields (Parr et al., 1983; Baker and Smith, 1987; Patriquin, 1988a). In well established cropping systems weeds are no greater a problem than in conventional systems (USDA, 1980; Robinson, 1985; Patriquin et al., 1987), even though weed incidence may be higher than on conventional farms. Many farmers, in fact, will tolerate and even encourage a certain level of weeds because of the valuable functions they perform, such as nutrient cycling, disease and pest control, soil and moisture conservation, and organic matter improvement as green manure (Altieri, 1987; Patriquin, 1988a). These benefits, however, are often difficult for scientists to isolate and measure (Patriquin et al., 1987; MacRae et al., 1989a). Savings associated with pesticide reduction or elimination vary with the extent of previous dependence and the efficiency and cost of previous practices.

D. Economic Considerations

1. Marketing Possibilities

It is important for farmers to maintain a secure income during the transition period. One strategy is to produce crops and commodities that provide more control over the price received at the farm gate (Friend, 1978; Hollander, 1985). This can be achieved by adjusting produce quality and variety to meet local consumer demand (Vail, 1987). For example, a farmer may be able to meet a local ethnic community's needs for an oriental leafy vegetable or health-food product. Most farmers also increase their security by diversifying their product offerings and marketing strategies. This reduces susceptibility to fluctuations in climate and price (Culik et al., 1983; Gliessman, 1985; Helmers et al., 1986). Farmers can grow crops to sell at farmer's markets, to food coops, through pick-your-own operations, and by contracting directly with groups of consumers. A mixed farm in Rhode Island provides an example (Table 10). This farm produces more than 10 crops, processes one (apples), markets them in different ways (including pick-your-own), and produces one for a specific consumer group (a group of southeast Asian descendants and immigrants).

Success with such approaches has meant that some farmers sell only their surplus production to wholesalers (Teichert and Schulz, 1987). A study in Colorado revealed that farmers received 44% higher gross returns with direct-marketing techniques compared to selling to wholesalers (US Bureau of Census, 1980 cited in Duhl et al., 1985). Selling locally helps minimize transportation costs, which may be relatively high when quantities are small and wholesalers far away (Carter and Lohr, 1986). Because of livestock reproductive cycles and short growing seasons in some locales, one of the greatest difficulties facing an individual farmer is the retailer's requirement for a steady supply of a diverse range of commodities. For example, free-range eggs and goat milk are difficult, and sheep milk almost impossible, to produce year round (Blake, 1987). Cooperative marketing is helpful because crop production and distribution can be coordinated to extend a product's period of availability or to avoid flooding a particular market at any given time (Teichert and Schulz, 1987).

Certain organically grown commodities may command a premium price, particularly vegetables, fruit, some grains, and beans. The mark-up over conventional prices is in the order of 10-50% but only 30-50% of organic farmers are currently able to sell some produce at premium prices (Lockeretz et al., 1981; Blobaum, 1983; Parr et al., 1983; Kramer, 1984). Even higher premiums are reported in Europe for fruits and vegetables (Geier and Vogtmann, 1984). For some producers, the availability of premium prices is the major motivating factor for converting to organic production. Certification standards have been developed (Soil Association, 1987; Mouvement pour l'Agriculture Biologique, 1988) and farmers making the transition should be aware of what production and handling standards must be met to be certified, since these standards serve to differentiate their products and help them achieve premium prices. Some standards even provide for an "in transition" category (Soil Association, 1987; Texas Department of Agriculture, 1988). The key elements of one set of certification guidelines are provided in Table 11. Aubert (1973) has cautioned that meeting certification standards may add a few years to the transition period.

Estimates of the potential financial advantages of premium prices, based on experimental data from Switzerland, are given in Tables 12 and 13 (Vogtmann et al., 1986a). In this example, the net farm income of a small dairy operation was 8.5% higher than a conventional dairy farm with a higher stocking rate. Differences were less dramatic for mixed-cropping systems. In both cases, however, the financial advantages of organic production may be underestimated because fixed costs were assumed to be almost equal, whereas they are invariably lower on organic farms.

Many farmers are not concerned, however, about certification and premium prices. A survey by Lockeretz and Madden (1987) of organic farmers in the US Midwest showed that few organic farmers felt that premium prices were an important advantage. Bateman and Lampkin (1986) concluded that premium prices, although a stimulus for conversion in the UK, have not been a main driving force. Grosch (1985), working in Europe, has concluded that premium prices are only financially critical to large-scale organic production systems.

2. Labour Requirements

When planning the conversion, most farmers assume that more labour will be required, at least in the short term. Most studies indicate that labour costs per unit of output are higher in sustainable farming systems (Oelhaf, 1978; Lockeretz et al., 1981; Lampkin, 1986; Wagstaff, 1987). This is because many operations, such as seedbed preparation and weed control, tend to be more labour intensive, or, if labour requirements are not higher, then yields may be lower. Because the extra labour is often provided from within the family, there may be no associated increase in cash labour costs (Wagstaff, 1987) unless off-farm earnings have to be sacrificed (Kramer, 1984). In some cases, labour requirements will gradually decrease during conversion, particularly in pasture systems where stocking rates have been decreased (Vine and Bateman, 1981), in small family-farm operations, such as those commonly found in parts of Europe (Vogtmann, 1984), and sometimes in fruit production systems where the need for weekly or biweekly spraying has been removed (Wagstaff, 1987). Because of greater crop protection and weeding needs, greatest increases in labour requirements are likely to occur in vegetable production systems (Oelhaf, 1978; Bateman and Lampkin, 1986; Reinken, 1986), and possibly soybeans (Enniss, 1985). One apparent consequence of the conversion process is a change in attitude towards farm labour. Many producers and their families feel more in tune with the biological processes of the farm, and the time spent becoming familiar with these processes is not regarded as an increased labour burden (Kramer, 1984; Brusko et al., 1985). In the long term, labour requirements seem most dependent on the ability of the producer to substitute knowledge, skills, and biological-control strategies for chemical inputs in the control of weeds, insects, and diseases (Mollison, 1979; Parr et al., 1983; Fukuoka, 1985).

3. Yield Projections and Financial Implications

It is difficult to generalize about yields during the conversion process. The literature reports an incredible range of results. Certain crops, however, appear to do as well or better in sustainable agricultural systems and may not suffer any yield decline during the transition period because of their particular growth patterns and the existing knowledge on which farmers can draw to avoid errors. Field crops in this category include hay, soybeans, oats, barley, and rye (Oelhaf, 1978; Lockeretz et al., 1981; Brusko et al., 1985). Corn usually declines in yield for a few years and then often recovers to previous levels, and, because of the long-term benefits of rotation, may even in some cases yield more than conventional corn (Culik et al., 1983; Crookston, 1984; Brusko et al., 1985). Other crops decline in marketable yield during the transition period and may not recover, especially if current cosmetic grading standards persist. Prices received may actually decline because grading systems are biased in favour of cosmetic food characteristics rather than nutritional quality. For example, minor insect damage on fruits and vegetables will often result in a lower grade and lower price even though the produce may be nutritionally superior to top-grade produce (R. van den Bosch et al., unpublished report to the EPA, contract 68-01-2602, 1977; Oelhaf, 1983; Riccini and Brunt, 1987). In a similar vein, US farmers producing range-fed beef generally receive a lower price than for grain-fed beef because the meat is not sufficiently marbled to qualify as Choice grade. Degree of marbling (intramuscular fat) is not, however, necessarily related to palatability and nutritional quality (McKinney and Gold, 1987). Changes to grading systems could improve the financial prospects of converting farmers.

Crops most likely to suffer a yield decline include potatoes (Oelhaf, 1978; Pimentel et al., 1984; Fischer and Richter, 1986), high-nutrient-demanding vegetable crops such as cabbage, leek, broad bean, and spinach (Reinken, 1986), and apples (Pimentel et al., 1984; Reinken, 1986; Wagstaff, 1987). Oelhaf (1978) reports that there may be a two- or three-year period in apple conversion during which no marketable apple yields are produced because of insect damage. Studies reviewed by Altieri (1986) suggest, however, that as we learn more about how to redesign the orchard environment, pest problems can be substantially reduced. To avoid financial disaster, producers are advised to find a market for products that are unlikely to make top grade before beginning the conversion process (Thorez, 1980). One Northeastern USA organic fruit and vegetable processor has estimated that organic growers may discard 20-40% of their crop for lack of an outlet not concerned about top cosmetic grade (Wander, 1988). Many processors, for example, are less concerned with the cosmetic quality of fruits and vegetables than are wholesalers who sell to the fresh market.

Yields of animal products per unit of land are likely to be lower during the conversion as stocking rates are lowered (Vine and Bateman, 1981; Hill, 1986). Milk production/cow may be as high as before conversion began (Lampkin, 1985b; Murphy et al., 1986), particularly if animals are selected for the feeding conditions found on low-input and organic farms (Boehncke, 1985; Murphy et al., 1986). Cows on diets that have been changed gradually to a very low-cost silage-hay/fodder-beets ration without any concentrates have continued to yield 5,000 kg milk/year (Vogtmann et al., 1986a). Organically raised animals usually have a longer productive lifespan than conventionally raised ones (Boehncke, 1985). As a result, lower annual yields of products, such as milk and eggs, may be offset by higher yields over the animal's lifetime, and because calving intervals can be shorter (Sarvas, 1981; Boehncke, 1986) more offspring may be produced. Studies reviewed by van Mansvelt (1988) suggest that fertility improvements are even more marked in the two generations that follow conversion.

Low-risk cropping systems during the transition period have been suggested by several investigators. Dabbert and Madden (1986), using a simulation model of field-cropping systems in Pennsylvania, concluded that a wheat-soybean-corn rotation on good soil, with purchase of chicken manure, was most profitable. On poorer land, a wheat-alfalfa (3 years)-corn (2 years) rotation was best with the manure applied on the wheat and corn. They also looked at the same cropping systems combined with a beef enterprise and concluded that it was more economical during the transition to grow cash crops and eliminate the beef enterprise. Nitrogen was provided by legumes and purchased manure. In another study, Brusko et al. (1985) and Peters (1987) concluded that an oats/red clover-red clover-grain corn-soybeans-silage corn rotation (not started with grain corn) provided returns over variable costs equal to a conventional corn-soybean rotation. Such suggestions are applicable only to areas in which corn and soybean are grown and in which off-farm manure is economically available. Buchner (1986), in Germany, suggested a 6-year rotation of grass/clover-winter wheat-oats-potatoes/vegetables-winter wheat-winter rye with undersown grass/clover, in which winter wheat and rye are the main cash crops. Similar studies are required in each region to find the optimal conversion rotations for its unique conditions.

V. Conversion Without Animals

A common question concerns the degree to which livestock are essential or desirable in sustainable farming systems. A mixed-cropping, pasture, and livestock system is generally seen to be most favourable for conversion (Vogtmann et al., 1986a). Livestock is important for its fertilizer contribution to the soil and because many animals eat forage that, although essential to most conversion rotations (for soil improvement, disease, and pest control), can often not be sold in local markets.

Some investigators doubt that soil fertility can be maintained in the long term without manure (Koepf et al., 1976; Hanley, 1980). The implication is that livestock-free farms must purchase manure, and at least one study has shown that this can be economically feasible during the transition period (Dabbert and Madden, 1986). Access to manure, however, may become a problem as more farms convert (USDA, 1980; Langley et al., 1983) or as the traditional intensive meat-production industries become more centralized and leave rural areas (Vail and Rozyne, 1982). It is easier to justify purchasing manure when producing fruits and vegetables (Aubert, 1973) as these are high-value crops, even without an organic premium price. Without livestock, legumes and green manure will be essential components of the rotation. Aubert (1973) recommends an annual legume cover at least once every three to four years, although vegetable producers may not find this necessary. Lampkin and Weller (1986) recommend more extensive use of legumes, but they caution against using the same legumes frequently or in the same way in the rotation (always undersown with oats for example) because of the potential for pest and weed build-up and nutrient depletion.

An example of a rotation for a system without livestock is given in Table 14 (Vogtmann et al., 1986a). Green manure (e.g., fodder radish, vetches, and cruciferous plants) are used throughout the 6-year rotation and, together with grain legume crops, they enable the rotation to maintain a positive N balance. This rotation differs from that recommended for a mixed farm operation (Table 9) in its greater reliance on green manure to supply N. Forage crops are replaced by grains and beans, which are more likely to have a market. A shorter, alternative rotation involves two years of cereals and a 1-year green manure (field beans, red clover, and possibly other legumes) that is cut and mulched several times but not harvested and is incorporated at the end of the year. Dugon (1984) has successfully used green manure in this way, starting his 5-year rotation with clovers that are cut and mulched, and following with wheat-rye-faba beans and wheat. In addition to nitrogen-fixing plants, he relies upon rock phosphate and guano for supplemental fertilization. He receives a premium price for both his organic wheat (50% higher than conventional) and rye (35% higher).

Peters (1987), working at the Rodale Research Centre in Pennsylvania, USA, reported that a 5-year organic cash-grain rotation (without animal manure) of oats/red clover-corn-oats/red clover-corn-soybean produced returns over variable costs lower than both a conventional corn-soybean rotation and a similar 5-year organic rotation with animal manure. In future years, this cash-grain rotation will be changed from a 5-year rotation to a 3-year one of winter wheat, then soybean drilled into the wheat-wheat broadcast into the soybean in the fall, and red clover seeded in the wheat in the spring and cut once during the summer, followed by incorporation in the fall-short season corn the next year, followed by winter wheat again. Peters predicts better returns because wheat prices usually exceed those of oats, overseeding will reduce tillage operations, and winter cover will reduce soil and nutrient losses. Wookey (1987) has concluded that immediate winter cover is an essential element of a conversion rotation.

In fruit production, manure, compost, green manure, mulches, foliar fertilizers, and rock powders can all be used (Oelhaf, 1978; Hall-Beyer and Richard, 1983; Page and Smillie, 1986; Reinken, 1986). Soil fertility problems in orchards are invariably minor compared with those associated with pests, diseases, and labour costs (Oelhaf, 1978; Pimentel et al., 1984). Page and Smillie (1986) provide a week-by-week guide to help fruit producers make the transition to sustainable practices.

VI. Implications of Widespread Conversion

Few studies have examined the implications of widespread adoption of sustainable agriculture. Most have focussed on conversion to organic agriculture because it represents an identifiable point in the spectrum of sustainable approaches.

A number of market commentators in North America and Europe feel that widespread adoption of organic agriculture is imminent. In Québec, the largest farm organization anticipates that over 40% of the producers in the province will be producing organically within 15 years (Hill, 1989). Growth rates for Canada as a whole are thought to be more modest but are estimated to be 15-25% per year, reaching 2% of total retail food sales by 1998 (Christianson, 1988). In England, Holden and Seeger (cited in Patterson and Bufton, 1986) have estimated organic output at 20-25% of the total by 2010. A study of California organic products sold at the wholesale level has predicted a jump in sales from $68 million (1988) to $300 million by 1992 (Franco, 1989).

The investigations attempting to analyze the impact of a major shift to organic/sustainable agriculture have been methodologically controversial, underscoring the need for more study in this area (Youngberg and Buttel, 1984; Madden and Dobbs, 1989). Existing studies have concluded that significant benefits would result, including improved food quality, enhanced environmental and human health, higher net farm income, and lower government subsidy payments and crop storage costs (Oelhaf, 1978; USDA, 1980; Langley et al., 1983; Vogtmann, 1984; Cacek and Langner, 1986; World Commission on Environment and Development, 1987). The effect on consumer food prices has been projected to be minimal (1% increase in total food expenditures [Oelhaf, 1983]) or substantial (up to 99% increases in some commodities [Langley et al., 1983]). Farm employment and farmer numbers could increase (Cornucopia Project, 1984; Enniss, 1985) and small- to medium-size farms could become more viable (CAST, 1980). There is concern about the availability of labour, however, as more conversions take place (USDA, 1980; Langley et al., 1983). Bellon and Tranchant (1981) fear that the aging farm population, in combination with the demand by young people for urban-style work conditions, could limit the number of farmers and farm labourers. Blake (1987), in contrast, points out that sustainable agriculture has some attractive work characteristics. He believes that relations with hired labour may be different than in conventional systems because the sustainable-agriculture philosophy stresses respect for all life forms, including fellow humans. In his opinion, these farmers may make greater efforts to provide employees with more educational opportunities and more challenging responsibilities.

Other difficulties to overcome include:

* Limited access to acceptable farm-scale sources of K for organic producers (Vogtmann et al., 1986a). Efficient recycling of wastes and soil conservation are seen as long-term solutions.

* Limited physical and economic access to manure. Farms that do not produce their own manure will find it increasingly difficult to purchase as more farms convert (USDA, 1980; Vail and Rozyne, 1982; Langley et al., 1983). Dependence on imported manure is not a long-term sustainable practice.

* Limited access to suitable equipment (e.g., tillage, manure, and slurry management), supplies (e.g., biocontrol agents), and services (e.g., pest monitoring, conversion advice).

* Limited financial assistance for farmers in great financial difficulty. Farmers with no financial flexibility cannot realistically attempt to convert without substantial financial assistance (Hanley, 1980; Aubert, 1982; Vogtmann et al., 1986a). Bateman and Lampkin (1986) have suggested that subsidies should be provided for capital-equipment investments, such as waste-handling systems, and annual payments as insurance against income fluctuations during the conversion period. The Advisory Panel on Food Security, Agriculture, Forestry and the Environment (1987) calculated that the costs of such subsidies could be recovered by government from the taxes paid by expanding and new sustainable agriculture enterprises (farms, retail and wholesale outlets, processors). Several European countries have recently developed such subsidy programs (Peter and Ghesquiere, 1988).

* The potential for limited access to traditional sources of credit (MacRae et al., 1988).

* Many government programs will need to be changed to provide a more supportive environment. MacRae et al. (1989b) have summarized existing Canadian governmental barriers to more widespread adoption. Goldstein and Young (1987) have demonstrated how USA federal price support programs make chemical-intensive farming more profitable than LISA systems. Dobbs et al. (1988) have shown how, in most cases, alternative systems perform better than conventional ones once price supports have been removed.

* The tendency in land tenure toward increasing concentration of land within fewer hands and the loss of prime agricultural land to non-agricultural uses. The empirical evidence is contradictory (Batie, 1986; Boehlji, 1987), but it appears that operators of large farms, although in an economically superior conversion position because of their access to resources (cf. Heffernan and Green, 1986), are generally less interested in the environment than owners of smaller farms (cf. Buttel et al., 1981). Farms on marginal land, however, are usually more difficult to convert than those on good land because of their more limiting physical and financial resources (Heffernan and Green, 1986). There is also considerable debate regarding the land base required to maintain acceptable production levels for domestic use and export. It is generally acknowledged that greater land area is required for diversified mixed cropping/livestock operations, but how this translates to nation-wide land demands is not clear. Investigators in the USA (Oelhaf, 1983) and Europe (Elm Farm Research Centre, 1987) have suggested that land set-aside programs would be unnecessary after a widespread conversion.

* Premium prices could decline in the long term as more organic food enters the marketplace (Duffy, 1987), yet this may not reduce net profits if input costs fall at the same time. As our understanding of agroecosystems increases, reliance on external inputs, and therefore operating costs, should decline. Oelhaf (1978), for example, estimated the cost of the conversion period as 5-20% of food prices, a cost that would decline with more information and support from agricultural institutions. Even with a price depressing increase in the supply of organically produced food, consumer demand is growing for these products which will moderate and could even offset the supply effect.

* Dislocations in the farm input industries, particularly fertilizers and pesticides (Enniss, 1985). However, it is unlikely that these industries would be traumatized since conversion will proceed incrementally, providing industries time to rationalize their operations.

* Food export potential is likely to decline over time (Langley et al., 1983), which will cause economic dislocations because so much of the North American agricultural economy is geared to export. This reliance on export is, however, a central reason why agriculture is in trouble at the present time. For example, there is some evidence that recently grains have been exported from North America and Europe at a net loss to the countries involved (Brian Oleson, Canadian Wheat Board, Seminar at Macdonald College, Nov. 3, 1987). In the long term, decreased dependence on export markets will benefit both developed and developing world producers (cf. Wessel, 1983).

There are signs that further research, extension, and education can help overcome these problems and barriers. The research needs of converting farmers are slowly becoming part of the mainstream research agenda (University of California Committee on the Sustainability of California Agriculture, Unpublished Interim Report to the University of California, 1986; Wisconsin Rural Development Center, 1986). A few organic farming consultants have been available for some time in some regions (Schmid, 1978; Aubert, 1982), but extension services are beginning to expand. A Farmers Own Network for Extension exists in the USA (Brusko et al., 1985), and a privately funded advisory service for organic farmers has been established in Britain (Blake, 1987). New university courses are being offered in faculties of agriculture in Canada, Europe, and the USA (Wisconsin Rural Development Center, 1986; Klster, 1987; Hill and MacRae, 1989).

VII. Conclusion

Recent research results confirm what experienced farmers have been saying for some time: conversion from conventional to sustainable production practices is possible in a reasonably short period of time. Financial risks can be minimized if the converting farmer plans ahead, identifies markets for products, converts the farm in stages, and gradually cuts expenditures on off-farm inputs. Developing cropping systems that balance the financial and biological needs of the farm will also reduce the chances of farm failure.

Although the general principles of conversion are reasonably clear, there remain many gaps in our knowledge. In many regions there are still few farmers who have experienced a conversion and few researchers interested in the process. Access to region-specific information can often make the difference between a smooth and a struggling transition. For those wishing to convert to organic production, markets for organic produce are not yet firmly established in many commodities and communities, and relatively little market research has been conducted. Taking a longer term view, new, but not insurmountable, problems will likely be created as more and more conversions take place, such as availability of manure and skilled labour. These potential barriers provide unique research opportunities to answer such questions as: Is manure a necessary requirement of sustainable farming systems or do animals just accelerate the cycling of nutrients through a farm? Is organic farming mining soil K resources? Can farming systems be designed that spread out labour requirements throughout the year? What adjustments will be required in input markets, and how can these be facilitated?

These information gaps should not discourage farmers from making the transition, except for those already in severe financial difficulty. Although some have failed in their attempts to convert, many have done so successfully, without great hardship, and have few doubts about the wisdom of their decision. They have found the benefits of converting to go far beyond the purely economic. Their skills and their appreciation of their environment have been enhanced; the health of their soil, animals, and families has improved; and many have a peace of mind that was absent when producing conventionally. Many are actively involved in efforts to make conversion easier and freely pass on their knowledge to other farmers and to scientists who are interested in studying the conversion process. For all these reasons we are likely to see many more conversions in the years ahead and an increased interest in the scientific community for sustainable farming systems.


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