Overlooked influence of Indian hemp (Cannabis sativa) cultivation on soil physicochemical fertility of humid tropical agroecosystems: Upland soils
2022
Kolo, J. | Ukabiala, M.E. | Osakwe, U.C. | Parah, J.B. | Nyamapfene, K. | Obalum, S.E. | Hassan, A.M. | Nnabude, P.C. | Igwe, C.A.
The extensive root growth of Indian hemp (Cannabis sativa) or Marijuana may imply greater depletion of soil nutrients. Because of the high demand for various parts of this plant especially the leaves that have smoking value, such nutrients may also not be recycled, impoverishing the soil the more. To empirically support or invalidate this hypothesis, this study compared soil physicochemical properties among uplands differing in Cannabis cultivation status; land not used for Cannabis cultivation (NUC), land currently under Cannabis cultivation (CCC), farmlands converted from Cannabis to alternative use (CAU), and Cannabis farmlands abandoned or seized (ABS) at a representative location in southwestern Nigeria. Particle size distribution of the soils differed under the land-use options. Soil bulk density exceeded the critical limit (1.30 Mg/m³) for crop production in these upland soils under CCC but not NUC, both for which values were lower compared to CAU and ABS. Soil pH, soil organic C, total N, available P, and cation exchange capacity were highest under NUC which had the lowest base saturation. The Ca²+ was lowest in CCC, but soil contents of K+, Mg²+ and Na+ were unaffected by Cannabis cultivation. Also, copper and manganese were highest in NUC and lowest in CAU, while iron was higher in ABS than the rest. Cannabis cultivation could compact the soil and decrease plant nutrient levels leading to a reduction in legitimate agricultural production below the soil potential.
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