Grain sorghum can be a high productive crop that requires adequate amounts of NPK fertilizer, with potentially deleterious effects on soils and groundwater. However, under harsh economic conditions, it may be cultivated in rotation with a legume crop benefiting from the nitrogen provided by the legume. After harvest, ploughing in the stubble can improve the organic matter status of the soil and help limit erosion. When sown in 20 cm rows, sorghum gives good protection from soil erosion. As a drought-tolerant species, sorghum improves water use efficiency while supporting relatively high levels of production in dairy cattle.
Toxic soils reclamation
Sorghum is tolerant of many pollutants and it thrives in toxic soils that kill most plants. Because of its penetrating root system, sorghum also captures the nitrogen which may be in excess in the soil, a property that has been useful in reclamation of fallow lands, where wastes have been discharged, and where soil N was very high (400kg/ha). Sorghum also thrives on salty irrigated soils: it restores the porosity of the soil making it possible to grow a high yielding wheat crop in one season (NRC, 1996).
Cover crop and soil improver
Sorghum can be used as a cover crop during the fall and winter: sown during the fall, it covers more than 60% of the soil before winter and protects it from wind erosion. It also helps through sparing more water than other cover crops because it dies quickly after the first frosts and does not withdraw water from the soil. After harvest, ploughing in the stubbles can improve the organic status of the soil and limit erosion (UC SAREP, 2006; NRC, 1996).
Weed and pest control
Sorghum has some detrimental effects on broad-leaf weeds, which are still effective after the sorghum has died. This could be due to phenolics and cyanogenics released by the sorghum roots that hinder weed growth (NRC, 1996).
Crop support
Dead stalks of sorghum grain can provide support to climbing legumes several months after the grain is harvested (NRC, 1996).