Overview of studies showing increased productivity from organic / sustainable agriculture practices
STUDIES SUPPORTING ORGANIC AGR / SUSTAINABLE AGR PRACTICES FEEDING THE WORLD: [From: Jules Pretty, “Resource conserving agriculture increases yields in developing countries,” Environmental Science and Technology 40, no. 4 (2006): 1114-1119, accessed July 4, 2014, doi: 10.1021/es051670d.] “Here we show the extent to which 286 recent interventions in 57 poor countries covering 37 M ha (3% of the cultivated area in developing countries) have increased productivity on 12.6 M farms while improving the supply of critical environmental services. The average crop yield increase was 79%” Paraphrase: These “interventions” include: Integrated pest management, integrated nutrient management, conservation tillage, agroforestry, aquaculture, water harvesting, and livestock integration. “Of projects with pesticide data, 77% resulted in a decline in pesticide use by 71% while yields grew by 42%” Paraphrase: Projects studied showed increase in productivity while also increased water efficiency and carbon sequestration and decreased pesticide use. [From: United Nations Conference on Trade and Development and United Nations Environment Programme, “Organic Agriculture and Food Security in Africa,” (New York and Geneva: United Nations, 2008), accessed July 4, 2014, http://unctad.org/en/docs/ditcted200715_en.pdf.] “Organic agriculture can increase agricultural productivity and can raise incomes with low-cost, locally available and appropriate technologies, without causing environmental damage. Furthermore, evidence shows that organic agriculture can build up natural resources, strengthen communities and improve human capacity, thus improving food security by addressing many different causal factors simultaneously” p.x “All case studies which focused on food production in this research where data have been reported have shown increases in per hectare productivity of food crops” p.x “Organic agricultural systems are making a significant contribution to the reduction of food insecurity and poverty in areas of Africa, and to an improvement in rural livelihoods” p.x Paraphrase: This study analyzed the crop yields of organic and near-organic agricultural projects in East Africa as well as Africa as a whole. Results find a 128 percent increase in crop yields in East Africa and the 116 percent increase in yields for all of Africa. p.16 [From: United Nations, Food and Agriculture Organization, “Organic Agriculture and Food Security,” (Italy, FAO: May 3-5, 2007): 5-7, accessed July 4, 2014, ftp://ftp.fao.org/docrep/fao/meeting/012/ah952e.pdf.] “Productivity in organic production systems is management specific. Studies suggest that switching to organic management commonly results in yield reduction in perennial crops (up to 50 percent) and during the conversion period for high external input systems in areas with favourable crop growth conditions (up to 40 percent) But in regions with medium growth conditions and moderate use of synthetic inputs, organic productivity is comparable to conventional systems (92 percent) and in subsistence agricultural systems, it results in increased yields up to 180 percent. Overall, the world average organic yields are calculated to be 132 percent more than current food production levels” p.5 “Organic soil management has been reported to increase soil aggregate stability due to increased soil organic matter and macrofuana that builds soil structure. Soil organic carbon is 14 percent higher in organic soils and the labile fraction is 30 to 40 percent higher, with important positive implications on plant nutrition. Enhanced microbial biomass improves soil physiological functions, such as faster phosphorus supply for plant growth” p.7 “Water-use efficiency: building active soils with high content of organic matter has positive effects on soil drainage and water-holding capacity (20 to 40 percent more for heavy loess soils in temperate climate), including groundwater recharge and decreased run-offs (water capture in USA organic plots was 100 percent during torrential rains). In Pennsylvania, organic corn yields were 28 to 34 percent higher than conventional in years of drought. In India, biodynamic soils have been reported to decrease irrigation needs by 30 to 50 percent” p.8 [From: Catherine Badgley et al., "Organic agriculture and the global food supply," Renewable Agriculture and Food Systems 22 no. 2, (2007): 86–108, doi:10.1017/S1742170507001640. (pdf found at http://www.organicvalley.coop/fileadmin/pdf/organics_can_feed_world.pdf)] Abstract: "The principal objections to the proposition that organic agriculture can contribute significantly to the global food supply are low yields and insufficient quantities of organically acceptable fertilizers. We evaluated the universality of both claims. For the first claim, we compared yields of organic versus conventional or low-intensive food production for a global dataset of 293 examples and estimated the average yield ratio (organic: non-organic) of different food categories for the developed and the developing world. For most food categories, the average yield ratio was slightly < 1.0 for studies in the developed world and > 1.0 for studies in the developing world. With the average yield ratios, we modeled the global food supply that could be grown organically on the current agricultural land base. Model estimates indicate that organic methods could produce enough food on a global per capita basis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. We also evaluated the amount of nitrogen potentially available from fixation by leguminous cover crops used as fertilizer. Data from temperate and tropical agroecosystems suggest that leguminous cover crops could fix enough nitrogen to replace the amount of synthetic fertilizer currently in use. These results indicate that organic agriculture has the potential to contribute quite substantially to the global food supply, while reducing the detrimental environmental impacts of conventional agriculture." [From: P. R. Hepperly, D. Douds, Jr., and R. Seidel, “The Rodale Institute Farming Systems Trial 1981 to 2005: Long-term analysis of organic and conventional maize and soybean cropping systems,” in Long-term Field Experiments in Organic Farming, ed J. Raupp et al., (2006): 15-31, ISBN 3-89574-590-1. Abstract: “Field investigations were conducted from 1981 to 2005 at The Rodale Institute Farming Systems Trial in Kutztown, Pennsylvania, USA to study the transition process from conventional to organic farming for maize and soyabean. Results indicated that many of the benefits of organic farming are related to soil C improvements. Among the benefits were: (1) increase in soil organic matter (soil C) and N, providing multiple benefits to the overall sustainability of organic farming systems; (2) organically managed crop yields on a per hectare basis can equal those from conventional agriculture; (3) during drought years, high soil organic matter under organically managed systems help conserve soil and water resources, thus stabilizing yields of the crops; (4) during overly wet conditions, high soil C content under organic management conserves soil N, leading to higher yield and protein levels compared with conventional system; (5) crop rotations and cover cropping typical of organic agriculture reduce soil erosion; (6) recycling of livestock wastes reduces pollution and accrues soil C on organic cropland; (7) abundant biomass both above and below ground (soil organic matter) also increases biodiversity which helps in the biological control of pests and increases crop pollination by insects; (8) use and benefits of organic farming technologies are not restricted to organic practitioners and may be adopted by conventional agriculturists to make their operations more sustainable and ecologically sound; and (9) organic farming reduces greenhouse gases and has multiple benefits for a wide range of other environmental concerns.” For more information on side-by-side comparisons of organic versus conventional agricultural practices, go to http://rodaleinstitute.org – can find lists of their peer-reviewed publications on all parts of agriculture from yields to soil health to emissions. CRITIQUES ON STUDIES OF ORGANIC AGRICULTURE [From: T. De Ponti, B. Rijk, and M. K. van Ittersum, “The crop yield gap between organic and conventional agriculture,” Agricultural Systems 108 (2012) 1-9] Abstract: "A key issue in the debate on the contribution of organic agriculture to the future of world agriculture is whether organic agriculture can produce sufficient food to feed the world. Comparisons of organic and conventional yields play a central role in this debate. We therefore compiled and analyzed a meta-dataset of 362 published organic–conventional comparative crop yields. Our results show that organic yields of individual crops are on average 80% of conventional yields, but variation is substantial (standard deviation 21%). In our dataset, the organic yield gap significantly differed between crop groups and regions. The analysis gave some support to our hypothesis that the organic–conventional yield gap increases as conventional yields increase, but this relationship was only rather weak. The rationale behind this hypothesis is that when conventional yields are high and relatively close to the potential or water-limited level, nutrient stress must, as per definition of the potential or water-limited yield levels, be low and pests and diseases well controlled, which are conditions more difficult to attain in organic agriculture.” “We discuss our findings in the context of the literature on this subject and address the issue of upscaling our results to higher system levels. Our analysis was at field and crop level. We hypothesize that due to challenges in the maintenance of nutrient availability in organic systems at crop rotation, farm and regional level, the average yield gap between conventional and organic systems may be larger than 20% at higher system levels. This relates in particular to the role of legumes in the rotation and the farming system, and to the availability of (organic) manure at the farm and regional levels. Future research should therefore focus on assessing the relative performance of both types of agriculture at higher system levels, i.e. the farm, regional and global system levels, and should in that context pay particular attention to nutrient availability in both organic and conventional agriculture." [From: V. Seufert, N. Ramankutty, and J. A. Foley, “Letter: Comparing the yields of organic and conventional agriculture,” Nature 485, (2012): 229-232, accessed July 6, 2014, doi:10.1038/nature11069] 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 impacts1, 2. Organic farming—a system aimed at producing food with minimal harm to ecosystems, animals or humans—is often proposed as a solution3, 4. 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 practices5. 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.” [From: K. W. T. Goulding, A. J. Trewavas, and K. E. Giller, “Can organic farming feed the world? A contribution to the debate on the ability of organic farming systems to provide sustainable supplies of food,” Proceedings-International Fertiliser Society 663, (2009): 1-27, accessed July 6, 2014, http://www.cabdirect.org/abstracts/20103163266.html.] Abstract: “A recent paper Badgley et al. (2007) claimed that organic farming, if used worldwide, would provide sufficient food for a growing world population. The paper stimulated much critical response. Our paper makes a critical assessment of this claim for wheat, a major cereal crop and source of food throughout the world. We consider the problems of using experimental yields in estimating the productivity of any crop or farming system and then look at farm yields, comparing organic and conventional systems. We examine in detail at the comparisons made by Badgley et al. and find many of them unsupportable: the ratio of organic:conventional wheat yields of 0.85 proposed by Badgley et al. we believe to be closer to 0.65. Nitrogen (N) fixation by legumes, the main source of N supply in organic systems, is shown to be much too small and variable to support large and consistent wheat yields of acceptable quality, and ideas that cereals could one day fix their own N found wanting. Our conclusion therefore contradicts that of Badgley et al. but agrees with that of a recent report by the University of Reading's Centre for Agricultural Strategy (Jones and Crane, 2009) that organic agriculture cannot feed the world using current technologies and with the meat-rich diet that people have or aspire to. We do, though, agree with Badgley et al.'s view that there is a need to improve soil quality by adding organic material, reducing over-optimal use of fertilisers and agricultural chemicals, and optimising rotations to reduce losses to pests and diseases. There is also, perhaps, a wider societal need for people to reconsider diet in the context of their health and the ability of the world to supply the wants of its anticipated 9 billion population.”