This month’s organism is the soybean (Glyine max), a globally important crop plant that originates from Asia. The seeds (called soybeans) are rich in protein (40% of dry weight) and contain a good mix of essential amino acids needed by humans (1). Not surprisingly, this makes soybeans and their products popular with vegetarians and vegans as a source of non-animal protein. However, soybean-protein is also widely used as the main protein source for intensive farming of animals including chickens, cows and pigs.
Growing soybean a very efficient way to produce protein in terms of land-use. Soybeans produce twice as much protein per area of land than other vegetables or grain, and around 15 times more than land set aside for meat production (2). The beans can be eaten whole after cooking (as in the Japanese dish edamame), but the majority of soybeans are processed to make a variety of soy-based food products, for example soya milk or tofu. Soy products are also added to many processed foods. Along with being rich in protein, soybeans are also rich in oil (20% of dry weight). The oil is extracted and used mainly for cooking with the remaining protein-rich pulp used as animal feed.
Soybean is a member of the legume family of plants. The seeds of other members of the legume family, including other beans, chickpeas and lentils, are also naturally protein-rich and widely cultivated. Legumes can afford to make their seeds more protein-rich than other plants can because they have a clever way for accessing nitrogen, an important plant nutrient required to make proteins. They can team up with soil bacteria called rhizobia to form a mutually beneficial relationship (symbiosis). In return for sugar and a place to live within the plant, the rhizobia convert nitrogen gas from the atmosphere into forms of nitrogen that the legumes can use. Relationships with rhizobia can give legumes a competative advantage over other plants, especially in low nutrient soils. Although rhizobia are naturally found in the soil, commercial strains of the Rhizobium species Bradyrhizobium japonicum are often applied to soybean fields to increase the number of symbioses established and maximise the nitrogen supply to the crop.
Cultivation of soybean began in China and Japan over 3000 years ago (3). During the 18th and 19th Centuries soybeans reached other regions including the Americas. In the USA it was mainly grown as a forage crop to feed livestock until the 1920s, when farmers were encouraged to grow it to increase the nutrient content of their soil (through release of excess nitrogen converted by the rhizobia). One of the soybean’s biggest supporters in the USA was Henry Ford, founder of the Ford Motor Company, who promoted the development of uses for soybean in food and industrial products (1). Today the largest growers of soybean are the USA, Argentina, China and India (1).
Like any other crop, cultivation of soybean is not without its challenges. Competition from weeds, damage by herbivores and diseases such as Soybean Mosaic Virus can all reduce soybean yields. One approach used in agriculture to better control weed populations is to grow genetically modified (GM) varieties of crop plants that are resistant to herbicides so that treatment with herbicide only kills the weeds, not the crop. The first GM herbicide-resistant soybeans were grown commercially in 1997. Since then, the use of GM soybean varieties has grown massively in many countries and by 2010, 93% of all soybeans grown commercially in the US were GM (1).
As a very land-efficient way of producing protein, it is likely that the demand for soybeans is going to continue to rise in the future. A challenge facing policy-makers is how to promote the production and consumption of soybeans without also promoting the destruction of some of the World’s most diverse natural environments, including the rainforests.
1) Wikipedia: Soybean (Retrieved 04/09/2014)
2) National Soybean Research Laboratory Soy Benefits (Retrieved 04/09/2014)
3) Laws (2010) Fifty plants that changed the course of history. David and Charles.