Article: organic and conventional yields

Re. their method, in order to avoid criticisms made of an earlier study by Badgley et al (see here) they (1) restricted their analysis to studies of ‘truly’ organic systems, defined as those with certified organic management or non-certified organic management, following the standards of organic certification bodies; (2) only included studies with comparable spatial and temporal scales for both organic and conventional systems; and (3) only included studies reporting (or from which they could estimate) sample size and error. Conventional systems were either high- or low-input commercial systems, or subsistence agriculture. Sixty-six studies met these criteria, representing 62 study sites, and reporting 316 organic-to-conventional yield comparisons on 34 different crop species

Conclusions:

“In short, these results suggest that today’s organic systems may nearly rival conventional yields in some cases—with particular crop types, growing conditions and management practices—but often they do not. Improvements in management techniques that address factors limiting yields in organic systems and/or the adoption of organic agriculture under those agroecological conditions where it performs best may be able to close the gap between organic and conventional yields.

Although we were able to identify some factors contributing to variations in organic performance, several other potentially important factors could not be tested owing to a lack of appropriate studies. For example, we were unable to analyse tillage, crop residue or pest management. Also,most studies included in our analysis experienced favourable growing conditions, and organic systems were mostly compared to commercial high-input systems (which had predominantly above-average yields in developing countries). In addition, it would be desirable to examine the total human-edible calorie or net energy yield of the entire farm system rather than the biomass yield of a single crop species. To understand better the performance of organic agriculture, we should: (1) systematically analyse the long-term performance of organic agriculture under different management regimes; (2) study organic systems under a wider range of biophysical conditions; (3) examine the relative yield performance of smallholder agricultural systems; and (4) evaluate the performance of farming systems through more holistic system metrics.

As emphasized earlier, yields are only part of a range of economic, social and environmental factors that should be considered when gauging the benefits of different farming systems. In developed countries,the central question is whether the environmental benefits of organic crop production would offset the costs of lower yields (such as increased food prices and reduced food exports). Although several studies have suggested that organic agriculture can have a reduced environmental impact compared to conventional agriculture, the environmental performance of organic agriculture per unit output or per unit input may not always be advantageous. In developing countries, a key question is whether organic agriculture can help alleviate poverty for small farmers and increase food security. On the one hand, it has been suggested that organic agriculture may improve farmer livelihoods owing to cheaper inputs, higher and more stable prices, and risk diversification.

On the other hand, organic agriculture in developing countries is often an export-oriented system tied to a certification process by international bodies, and its profitability can vary between locations and years. There are many factors to consider in balancing the benefits of organic and conventional agriculture, and there are no simple ways to determine a clear ‘winner’ for all possible farming situations.”

The article ends with this eminently sensible comment “… instead of continuing the ideologically charged ‘organic versus conventional’ debate, we should systematically evaluate the costs and benefits of different management options. In the end, to achieve sustainable food security we will probably need many different techniques—including organic, conventional, and possible ‘hybrid’ systems—to produce more food at affordable prices, ensure livelihoods for farmers, and reduce the environmental costs of agriculture.”

Abstract

Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts. Organic farming—a system aimed at producing food with minimal harm to ecosystems, animals or humans—is often proposed as a solution.However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions— that is, with good management practices, particular crop types and growing conditions—organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.

Reference

Seufert V, Ramankutty N and Foley J A (2012).  Letter: Comparing the yields of organic and conventional agriculture, Nature doi:10.1038/nature11069

You can download the paper here (subscription needed).

An earlier paper by two of these three authors (Foley and Ramankutty) is also worth reading – and is summarised on the FCRN website here.