Cover crop, soil improver and green manure
Pigeon pea is used as a contour hedge in erosion control (Bekele-Tessema, 2007). An N-fixing legume, it does not need inoculation before sowing. It was reported to fix 40-97 kg N/ha/year in Africa and up to 235 kg N/ha/year in Florida, 88% being used for pods and seeds formation. Pigeon pea cultivation could provide 40-60 kg N/ha to the following crop (Valenzuela, 2011). Pigeon pea had a large residual effect on maize, increasing grain yield by 57% and total plant dry matter by 32% (Kumar Rao et al., 1983). The extensive root system of Cajanus cajan improves soil structure by breaking plow pans, and enhancing water holding capacity of the soil (Crop Trust, 2014; Mallikarjuna et al., 2011). Its deep taproot is able to extract nutrients (e.g. P) from the lower layers of the soil and deposit them in upper layers where they can benefit other crops (Valenzuela, 2011). The leaves and immature stems can be cut and used as a green manure (OAF, 2015). Fallen leaves act as a mulch and are estimated to return about 40 kg N/ha to the soil. They also return organic matter, which helps in preventing erosion due to heavy rains, and reduces soil temperature (Ecocrop, 2016).
Windbreak and shade provider
Tall varieties of pigeon pea are reported to be good windbreaks. Pigeon pea is able to provide shade to young coffee or vanilla plants, and to forest seedlings in nurseries (Valenzuela, 2011).