Mesquite is an N-fixing legume. Its roots are infected by cowpea-type Rhizobium and also form mycorrhizal associations with Glomus fungi. The N-fixing rate increases when both mycorrhiza and Rhizobium associations are present. A 6 m x 6 m mesquite plantation can fix about 30-40 kg N ha/year (Orwa et al., 2009) and may subsequently be intercropped with maize or with Cenchrus ciliaris L., Megathyrsus maximus Jacq. and Opuntia spp. (van der Maesen et al., 1997).
Mesquite provides shade and shelter and is used in windbreaks and shelterbelts, but it should be avoided in irrigated areas since it is a potential host to pathogenic nematodes (Ecoport, 2010). Because of its ability to grow on saline and alkaline soils, mesquite is valued as a soil reclaimer in very poor and degraded lands, rocky soils or abandoned copper mines. It is also useful for stabilizing dunes in coastal zones and bunds around mangrove creeks (van der Maesen et al., 1997). Mesquite has an overall positive effect on soil: N, sulphur, organic matter and soluble salts are increased threefold within the upper 4.5 m of soil under mesquite (Ecoport, 2010).
In spite of these qualities, mesquite is considered as a noxious weed in many parts of the world, since it naturalizes easily and competes strongly with other species when introduced into areas where soils are better and the climate more humid (USDA, 2010; Ecoport, 2010; Ecocrop, 2010; van der Maesen et al., 1997). In Rajasthan (India), sheep farmers have to face the problem of the infestation by Prosopis juliflora bushes on already scarce grazing areas (Dinesh et al., 2003). It is possible to control mesquite by regular pruning and turn it into a valuable tree that is less aggressive to grasses or crops. Removing the poorly nutritive side branches results in smaller roots and more efficient water utilization (Elfadl et al., 2003). Grazing of mesquite stands is another way to control its growth (Riveros, 1992).