Purple Bush-Bean

M. atropurpureum is a tropical herbaceous dicot belonging to the family Fabaceae. It rapidly develops dense, hairy, dark green vines about 5 mm in diameter, until it reaches its mature size around 120 cm. The vines have bright green trifoliolate leaves, which are roughly 2–7 cm long with smooth hairs on the underside. Flowers are dark reddish purple. The seeds are small brown peas with a white spot, found in the plant's pods which hang on the vines in bunches of about 5–10. In weather and soil conditions favourable to the plant, stem nodes close to the soil may root, enabling vegetative propagation of the plant. M. atropurpureum forms a deep swollen taproot up to 2 cm in diameter.

M. atropurpureum is also commonly referred to as 'Siratro' or 'Aztec' (modified races to improve nematode resistance and reduce rust sensitivity, respectively) atro, purple bush-bean (a common English term for the species), Purpurbohne (a common German term for the species), or conchito (a common Spanish name for the species). It has a short lifespan, but a high density, with a minimum of 1200 and a maximum of 1700 plants per acre when it is in season and free to grow. M. atropurpureum is native to Central and South America, as well as the Caribbean Islands, and has been known to grow in some regions of southern North America, including Mexico and the US in states such as Arizona, Texas, Florida, and Hawaii, as well as coastal regions in Queensland and New South Wales, Australia, and scattered regions across Africa. Its historical use has been to serve as pasture for domesticated livestock, and was the first tropical pasture improved by breeding. Performed in Australia in 1960s, native M. atropurpureum was bred to resist nematodes in its roots, which created a modified species known as 'Siratro', which developed a rust sensitivity, so 'Aztec' was developed to counter the arisen problem in 1995. On indigenous North and South American farms where M. …

One of the most strategic advantages to M. atropurpureum is its ability to grow and prosper in varied soil types. It is propagated naturally by legumes bursting and sending seeds forcefully into the ground. Growing season varies geographically, but typically will be in the spring and summer. It can be grown in soils that are coarse and fine, as well as all variations between. Primarily, it is grown on pasture fields interseeded with a grass to retain the soil and prevent erosion. M. atropurpureum is often found by roadsides, in vegetation around waterways and coastal regions, and on disturbed ground. M. atropurpureum can grow in soils with a pH level as low as 5.0 and as high as 8.0. It can also survive in most temperatures, requiring a minimum temperature of 23 °F, and has an average salinity and shade tolerance. It requires an average precipitation between 15 and 111 cm. M. atropurpureum has been tested on several occasions to find additional benefits. When used on a cow pasture intercropped with traditional grass in Australia, it improved milk yield by 2 kg per day. It also improved yields from domestic animals such as goats in Kenya, Zambia, Tanzania, and other African countries. Because of its nitrogen-fixing abilities as a legume, M. …