Short communicationOrganic agriculture cannot feed the world
Introduction
Organic agriculture (OA) currently occupies 0.3% of agricultural land, mostly in developed countries. This land is farmed according to rules administered by various OA-regulating associations that, in the case of crops, disallow the use of most inorganic compounds for crop nutrition, synthetic compounds for pest, disease and weed control, and more recently, genetically modified cultivars. The rules also encourage rotations and intercrops to build soil fertility, improve crop nutrition, and to control or limit production problems associated with pests, diseases, and weeds. These latter aspects of OA are practiced much more widely outside OA, but those systems, here referred to as conventional agriculture (AG), vary enormously in range and amount of ‘OA-prohibited’ inputs. They include, for example, many farms in developing countries where agrochemicals are not used because they are either not available or are too expensive.
The acceptance of OA in developed countries is increasing, albeit more slowly than in the previous decade, driven by consumer concern for food and environmental safety and supported by premium prices that consumers will pay for OA-labelled products. The biggest markets are in USA, where 0.3% of agricultural land is devoted to OA, and Europe with 3.4%, where additional subsidies are available. At the same time, AG is also responding to the same food and environmental safety concerns with alternative labels developed by food retailers based on ‘good farming practices’ for products from production systems that integrate the use of agrochemicals with biological processes. The same trends are evident in developing countries too, but the markets for labelled products are smaller and price premiums depend on the access they give to export markets in developed countries.
An important issue to the acceptance of OA is found in the question of its productivity. Existing analyses have put the carrying capacity of OA at 3–4 billion, well below the present world population (6.2 billion) and that projected for 2050 (9 billion). Those analyses (Buringh and van Heemst, 1979, Smil, 2001, Smil, 2004) are based on the performance of OA systems as practiced in C19 before the widespread use of inorganic fertilizers and when the world population was around 1 billion. They remain relevant to the present discussion, because advances in crop yield since those times have not changed the essential metabolism of plant growth and nutrient requirement to support it. A recent paper by Badgley et al. (2007) has reopened this debate by presenting an analysis purporting to show that OA cannot only greatly increase productivity in developing countries but could feed the entire world also. The paper, initially presented in May 2007 at the FAO Conference on Organic Agriculture, has received much attention in the popular press and science magazines, e.g. New Scientist (2007). OA does not need the ability to feed the world to contribute within agricultural production but this report provides some with justification to solve perceived and real production and environmental challenges in agriculture and food supply in a single step by large-scale transformation to OA. In this, the alternative development paths that resource-poor farmers of the developing world might take are a particular focus of attention. The conclusions of the study are, however, invalid because data are misinterpreted and calculations accordingly are erroneous.
Section snippets
A major overestimation of the productivity of OA
Badgley et al. (2007) estimate OA productivity by applying OA/AG yield ratios calculated from the literature to national food production statistics from the FAO database. For developed countries the ratios are dominantly between high-yielding crops well supplied with either organic nutrients (OA) or fertilizer (AG). The mean ratio is 0.91. For developing countries, in contrast, the ratios (mean 1.74) are obtained largely from comparisons of low-yielding crops that received either organic
On the limited availability of organic nutrients
If large-scale conversion to OA were possible, where would the organic nutrients to support the high productivity required to feed a large and expanding world population come from? The second part of Badgley et al. (2007) seeks to confirm the conclusion of adequate productivity of OA by a parallel estimate of the potential of leguminous cover crops to provide the required organic N. A survey of published N-fixation rates and crop performance in legume rotations is used to establish equivalent N
An evaluation of the productivity of legume-based agriculture
Fortunately, there is a way to evaluate the legume-based cropping strategy proposed by Badgley et al. (2007). The provision of 100 kg N/ha fertilizer equivalent to all cropland would support, with inevitable in-crop losses to drainage and volatilisation of say 25% (Crews and Peoples, 2004), the production of 4170 kg crop dry matter/ha at 1.8% N. That amount of crop growth would, with a creditable harvest index of 0.4, establish an N-limited cereal yield of 1.7 t grain/ha, sufficient over 1362 Mha
Conclusion
A critical analysis of the nature and use of OA/AG yield ratios does not support the proposition that large-scale OA productivity would be sufficient to feed the world or that legume cover crops could replace N fertilizer use without disrupting current food production. There is, therefore, no newly established production frontier for OA so that those who use the conclusions of the study by Badgley et al. (2007) to promote or support OA will have been misled and limited resources for research
A way forward
Transformation to OA is, of course, not only about N supply but rather the interaction of a number of social, environmental and economic concerns and outcomes. Important issues include maintenance of soil condition, provision of nutrients other than N, human labour, control of pests, diseases and weeds, product quality and safety, and minimizing off-site environmental effects. Surely now is the time, for unbiased analyses of alternative agricultural production systems in the search for optimal
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2022, Agricultural SystemsCitation Excerpt :Comparisons from experimental plots that propose higher ratios around 0.75–0.91 (Badgely et al., 2007; Seufert et al., 2012; Ponisio et al., 2014) are, however, more widely used. Various authors (Connor, 2008; Goulding et al., 2011; Connor, 2018) have explained that crop yield ratios cannot estimate the relative productivity of OA because they overlook the land, a limited global resource, that must be maintained in legume crops and pastures to provide the biologically fixed nitrogen (BNF) upon which continuing productivity of OA entirely relies. Before the use of crop yield ratios to estimate the relative yield of OA, it was generally accepted to be much smaller than CA and probably sufficient to feed a world population of around 3–4 billion (Buringh and van Heemst, 1979; Smil, 2000).