Changes in soil physical and mechanical properties under different tillage and cropping systems in alfisol soil of southwestern Nigeria

Sustainable agricultural strategies such as conservation agriculture (CA) and integrated land management are required to mitigate land degradation and food insecurity. This study was conducted to investigate the effects of different cropping systems: sole sorghum (SOR), sole cowpea (COW), sole soybean (SOY), sorghum-cowpea intercrop (SC), and sorghum-soybean intercrop (SS); and tillage practices: conventional tillage (CT), no tillage (NT), and compacted no till (NTc) on physical and mechanical properties of an Alfisol in Southwestern Nigeria. The experimental layout comprised a split plot design accommodating the 3 tillage and 5 cropping systems in a randomized complete block design with three replications. Undisturbed soil samples were collected from 0 to 15 ​cm, and 15–30 ​cm soil layers for the determination of soil bulk density (BD), total porosity (TP), and unconfined compressive strength (q_uf). The results showed that bulk density was lower, while total porosity was higher under intercrops than monocrops in all the tillage treatments. Conventional tillage had the least BD compared to no tillage and compacted no till plots. Soil vane shear strength (Ʈ) and unconfined compressive strength (q_uf) were generally lower under the intercrops than the sole sorghum plots. Averaged over the two soil depths, the mean soil q_uf of SS intercrop was 1.28 times lower than the mean soil q_uf of SOR but was 1.06 times higher than the mean soil q_uf of SOY. SC intercrop had a 14.20% and a 9.15% lower average soil q_uf than SOR and COW in 2019. Unconfined compressive strength and vanes shear strength significantly positively correlated with BD and negatively with TP, organic carbon (OC), organic matter (OM), and total nitrogen (N) in both cropping years. The research demonstrates that farming approaches that integrate soil cover preservation and minimal soil disturbance with diverse cropping systems improve soil physical and mechanical behavior.