Maize and sorghum root growth and yield when intercropped with forage grasses

Integrated crop–livestock systems that intercrop forage crops with grain crops are effective for increasing forage production and improving nutrient cycling and soil health. However, the potential for root competition when maize (Zea maysL.) and sorghum [Sorghum bicolor(L.) Moench] are intercropped with forages in sandy soils is unknown. The objectives of this study were (a) to evaluate the root growth and production characteristics of maize and sorghum intercropped with forage grasses and (b) quantify above‐ and belowground biomass in a tropical integrated cropping system. Two 3‐yr experiments were conducted in which maize and sorghum were intercropped with forage grasses: guineagrass (Panicum maximumJacq.), ruzigrass [Urochloa ruziziensis(Germ. & Evrard) Crins], palisade grass [Urochloa brizantha(Hochst ex A. Rich.) R. Webster], or an Urochloahybrid. Monocropped maize and sorghum were used as controls. Fine roots (≤3 mm) were sampled in the monocropped and intercropped systems at soil depths of 1.0 m. Intercropping guineagrass and palisade grass with maize and sorghum resulted in 40% greater dry matter production than intercropping with ruzigrass and the Urochloahybrid. The positive effect of intercropping forage grasses in the low‐fertility sandy soil was greater for sorghum than for maize because of lower root growth competition. On average, intercropping maize and sorghum with forages increased the total above‐ and belowground biomass by 30 and 50%, respectively, compared with monocropping. In summary, intercropping maize and sorghum with forage grasses is a viable option to enhance biomass during the off‐season in tropical integrated crop–livestock systems. Intercropping sorghum and maize with grasses is viable for enhancing off‐season biomass.Sorghum production characteristics are not influenced by intercropping with grasses.Competition with grass is stronger for the root system of maize than of sorghum.