Invasive species
Though Neonotonia wightii was first assessed for land restoration due to its protective effect against erosion, it is now considered to be an invasive species in Hawaii as it may smother more desirable species (US Forest Service, 2011; Ziegler et al., 2000).
Soil improver, pests and weed controller
Neonotonia wightii is an N-fixing legume, and as such enhances the N status of the soil. It can help restore degraded soils very quickly, prevent erosion and suppress weeds. For example, in Cuba, it has been used in organic citrus plantations (Alföldi et al., 2002). Perennial soybean may have a double protective effect in banana plantations: its deep taproot explores the deepest parts of the soil while banana roots develop horizontally. There is thus no competition for soil nutrients and perennial soybean provides N to the banana plants. As a cover crop, perennial soybean prevents banana plantations from being invaded by weeds and it might alleviate nematode attacks (Risède et al., 2010).
Fallow crop, cover crop and intercrop
Neonotonia wightii has been used in small areas of Papua New Guinea as a fallow crop in abandoned gardens, as a cover crop and for woody weed control in overgrazed pastures (Pengelly et al., 1992). Perennial soybean may also be intercropped with cereals in semi-arid areas since it shows good perennation and regeneration. Its moderate growth during the first year lets the cereal grow without heavy competition (Njarui, 1988). Perennial soybean has also been used in mixed pasture with green panic (Megathyrsus maximus var. pubiglumis) in order to restore soil fertility after continuous maize cropping (Partridge, 2003).