Green manuring with sunnhemp is an age-old practice. Sunn hemp, a tropical plant primarily grown as a cover crop or green manure, has increased dramatically in popularity over the last decade, Sunnhemp can be grown as dual purpose also i.e. green manure as well as fibre crop because after harvesting of fibre crop, the top portion (30 cm from top) can be incorporated in to the soil, which substantially increase the yield of succeeding crop .

Its needed under present era of chemical fertilization, it enhances sustainable development of agricultural production system. Its cultivation is done all tropical country where amendments and amelioration of soil is needed.

Probably you won't get reliable information on extent of use. But, look at the seeds sold or marketed in each country, you may get some idea. It's uses are widely reported.