Can Organic Crop Production Feed the World?

Abstract

Agriculture provides the most essential service to mankind, as production of crops in sufficient amounts is necessary for food security and livelihood. This chapter examines the question of whether organic agriculture can produce enough food to meet future demand. This question relates to a moral imperative and any evaluation must therefore be based on objective scientific facts excluding ideological bias, political correctness, economic incentives or environmental opinions. The chapter begins by defining the conditions necessary for a stringent evaluation of crop yields and explains potential pitfalls. Yield data from national statistics, organic and conventional long-term experiments and comparative studies are then compiled and evaluated, followed by a discussion of the main factors behind low-yielding production. In a global perspective, the scientific literature shows that organic yields are between 25 and 50% lower than conventional yields, depending on whether the organic system has access to animal manure. The amount of manure available on organic farms is usually not sufficient to produce similar crop yields as in conventional systems and therefore green manures are commonly used. However, organic crop yields reported for rotations with green manure require correction for years without crop export from the field, which reduces average yield over the crop rotation. When organic yields are similar to those in conventional production, nutrient input through manure is usually higher than nutrient addition in conventional agriculture, but such high inputs are usually only possible through transfer of large amounts of manure from conventional to organic production. The main factors limiting organic yields are lower nutrient availability, poorer weed control and limited possibilities to improve the nutrient status of infertile soils. It is thus very likely that the rules that actually define organic agriculture, i.e. exclusive use of manures and untreated minerals, greatly limit the potential to increase yields. Our analysis of some yield-related statements repeatedly used by advocates of organic agriculture reached the following conclusions: Organic manure is a severely limited resource, unavailable in quantities sufficient for sustaining high crop yields; legumes are not a free and environmentally sound N source that can replace inorganic fertilisers throughout; and low native soil fertility cannot be overcome with local inputs and untreated minerals alone. 2Agricultural methods severely limiting crop yields are counter-productive. Lower organic yields require compensation through expansion of cropland -the alternative is famine. Combining expected population growth and projected land demand reveals that low-yielding agriculture is an unrealistic option for production of sufficient crops in the future. In addition, accelerated conversion of natural ecosystems into cropland would cause significant loss of natural habitats. Further improvement of conventional agriculture based on innovations, enhanced...

Ecosystem Services in Biologically Diversified versus Conventional Farming Systems: Benefits, Externalities, and Trade-Offs

“…In developing nations, they found a mean yield increase of 174.6% (with a 95% confidence interval of 156.0 to 191.2%) when diversified farming practices were employed, compared with resource-poor (generally subsistence) farming strategies (138 comparisons from 29 studies). These results were contested, however, by authors who suggested that organic management would produce similar yields only if off-farm sources of manure were utilized, or when utilizing leguminous noncrop rotations that would decrease overall yields over the full crop rotation cycle (Kirchmann et al 2008). Subsequently, two new studies (de Ponti et al 2012, Seufert et al 2012) critiqued the Badgley et al (2007) study, primarily based on the choice of studies included in the Badgley study.…”

Agroforestry—The Next Step in Sustainable and Resilient Agriculture

“…Soil quality tends to improve under organic management based on measurements of soil organic matter [39,41], though no-till conventional agriculture measured highest of all in some studies [9]. Although organic yields typically lag behind conventional yields [42], in drought years the opposite has been shown, which is attributed to the higher water holding capacity of soils under organic management [43,44]. Overall, organic production uses less energy per production unit due to the high energy costs of conventional fertilizer and pesticides [39,44,45].…”

“…However, it can be a challenge to grow the necessary biomass in the cover crop to provide effective weed control, and the technique may not be possible in water-limited environments due to water competition by the cover crop [37]. Perennial weeds pose a particular problem, as they are typically able to grow through the mulch [37,42,55].…”

“…Organic systems are generally agreed upon as less productive, with an average decrease in yield of around 20% to 25%, though the literature shows ranges anywhere from 5% to 50% depending upon the crop, soils, intensity of management, and methods by which the study was conducted [38,42,57]. Critics argue that under organic management, more land would need to be put into agricultural production in order to maintain global food security.…”

Enhanced top soil carbon stocks under organic farming

“…Although these data clearly showed that organic management increased SOC, it is often criticized that increased SOC stocks originate from massive imports of organic matter taken from elsewhere (13,17,18). To examine the potential impact of imported organic matter, we analyzed a subset of studies representing organic farming systems with zero net input separately.…”