N-fixing legume and green manure
Hairy indigo is a N-fixing legume that could provide 126 kg N/ha/year to companion grasses and 100 kg N/ha to maize crop when sown as a relay crop (Djarwaningsih, 1997; Kalmbacher et al., 1980). In maize-hairy indigo system, hairy indigo provides also about 4-5 t DM/ha. Research on its utilization as green manure was reported to be abandoned in the 1990s (Djarwaningsih, 1997).
Cover crop and nematode controller
When sown as a relay crop of maize, hairy indigo not only provides N to the crop and organic matter but it also protects the soil from erosion. Its role in erosion control may be important and it is recommended for hilly areas (Djarwaningsih, 1997). Hairy indigo was reported to have reducing effect on nematodes when used as a cover crop or as an intercrop in rotation with legumes such as peanuts or soybeans (Rodriguez-Kabana et al., 1988; Rhoades, 1983).
Hairy indigo is a very versatile species that re-seeds readily after fruiting and may become invasive. In 1918, it was already declared a noxious weed in Australia (Gilruth, 1918) and is now classified as invasive in many places, including Australia (where it is classified as "reject for import"), French Polynesia, Palau, Nauru, the Philippines, Singapore, Diego Garcia Island, and Mayotte Island. It is a known weed in the USA ("High risk" species in Florida), China, Puerto Rico, and Brazil (CABI, 2014; Randall, 2012; US Forest Service, 2010).