Adapting the cultivation of industrial hemp (Cannabis sativa L.) to marginal lands: A review

Marginal lands are increasingly being considered for cultivating industrial and bioenergy crops to reduce the direct and indirect land-use changes. This review investigates the feasibility of hemp (Cannabis sativa L.) cultivation under the biophysical constraints that characterize marginal lands, with the objectives of (i) determining to which extent hemp cultivation can be affected by the considered factors of marginality and (ii) determining the most pertinent adaptations of crop technical management. This work establishes that hemp is a species that can be considered particularly susceptible to adverse conditions, in particular regarding soil characteristics (heavy clay, coarse sand, shallowness) and dry climates. Heavy metals (HMs) contaminations do not appear to severely limit hemp's productivity, with the exception of thallium. The adverse effects of HMs on the profitability of hemp cultivation rather lie in limitations of the potential uses of hemp biomass for several end-uses applications (e.g., textiles, food) because of the HM contents in the raw materials. On HM polluted soils, a single-use fiber production destined to high-added value applications such as bio-based composites is the most suited production. Under dry climate, hemp productivity might be particularly affected depending on the soil quality and on the severity of the dryness. Hemp can be suited for mountain environments, in which the potential for harvesting the threshing residues as a source for medical application of cannabinoids might provide a supplemental added-value to the crop. Overall, although hemp has often been considered as able to grow in harsh conditions, this review highlights that care should be given to such statements and hemp appears to be more suited for integrating conventional agro-systems, in particular considering that it can be considered both as a food and industrial crop.