The role of biological nitrogen fixation by non-legumes in the sustainable production of food and biofuels

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The 12th International Symposium on biological nitrogen fixation (BNF) with Non-Legumes took place in Buzios, Rio de Janeiro, Brazil from October 3 to 8, 2010. It was the latest in a series of meetings that, fittingly, first began in Brazil, in 1977 in the city of Piracicaba. This Special Issue of Plant and Soil comprises 21 papers from the Buzios Symposium, as well as a commentary and three obituaries. Given the volatility (and general upward trend) in oil prices and global attempts to alleviate greenhouse gas (GHG) emissions associated with the agricultural use of Ncontaining mineral fertilizers produced by the energyintensive Haber-Bosch process, it was inevitable that the main focus of the 2010 Symposium would be very much on the substitution of fertilizers in favour of the increased use of BNF in non-legume cropping systems. In the intervening years since the last time the symposium was held in Brazil (August 1987 in Rio de Janeiro), knowledge about non-legume BNF has increased enormously, encompassing everything from more accurate N-based quantification studies in the field through to the molecular identification of their associated diazotrophs (both culturable and unculturable) and the localization of these bacteria via high resolution microscopy. The completely sequenced genomes of many diazotrophic bacteria are also now available, and more are deposited in databases every year. Indeed, such technologies, which only a few years ago were considered remarkable, are now becoming standard tools in this field. In the case of sugarcane and other biofuel crops, the location of the 2010 meeting in Brazil was especially pertinent, as the highly advanced Brazilian bioethanol programme, which produces over 27 billion litres of ethanol per year, is based upon the cultivation of sugarcane, and Brazilian cane has long been known to be able to derive much of its N-requirements via BNF. The consequent low fertilizer use by Brazilian cane producers not only makes for enormous economic savings, but also mitigates against GHG emissions from the production of N-containing fertilizers, as well as their transport and application and nitrous oxide emissions. However, in spite of the strong likelihood that cane can benefit significantly from BNF, little is known about how much N it can really fix, and as field-based BNF quantification studies may take several years to complete, we are thus fortunate to include two such studies in this Special Issue (both utilizing the N natural abundance technique): one on sugarcane by Urquiaga et al., and one on the C-4 “energy crop” Plant Soil (2012) 356:1–3 DOI 10.1007/s11104-012-1317-1