Sunn hemp, a tropical legume species, as an alternative bioenergy feedstock in temperate climates

The agricultural sector is called to take prompt action to find solutions capable of guaranteeing large quantities of lignocellulosic biomass to the increasing bio-energy production demands in a rational and sustainable manner without negatively affecting the food supply. An effective way to do that could be through the development of integrated cropping systems, where promising legume crops could be introduced within crop rotations gaps. The objective of this study was to characterize the agro-physiological performance of sunn hemp (Crotalaria juncea L.), a fast-growing high lignocellulose yielding multipurpose leguminous crop of tropical origin, within a traditional sequential cropping system in a temperate climate. Between 2016 and 2022, field trials dealing with: i) cultivar performance at different harvest times, and ii) soil tillage method, were carried out. It has been shown that sunn hemp, besides its potential positive effects on the soil fertility and regardless the cultivar, can produce acceptable biomass yields (ranging from 2.4 to 13.7 Mg ha⁻¹) in a relatively short time, when sowed under no-tillage conditions and harvested around the full flowering stage (about 90 days after sowing). Some physiological parameters (i.e. photosynthesis and photochemical efficiency processes) corroborated the overall good adaptation and performance of sunn hemp under temperate conditions. This preliminarily dataset indicate that such agronomic practices besides maximizing lignocellulosic biomass production may render logistically feasible the cultivation of sunn hemp within a traditional crop rotation in a temperate climate.