Abstract
Various species of cultivated thistle, such as Cynara cardunculus L. (cardoon), exhibit interesting features for industrial biomass production as bioenergy crops, given also their advantageous adaptation capacities to typical Mediterranean climate trends, with noticeable resilience to drought and salinization stresses. The in situ hyperspectral reflectance responses of three genotypes of cardoon plants, irrigated with water at different salinity levels, have been tested for assessing the effects on their biophysical parameters, aiming at improving the biomass yield for bioenergy production, minimizing at same time the environmental impacts and the exploitation of soils and waters resources. The leaf and canopy reflectance hyperspectral signatures, acquired at three different growth stages with biometric measurements, were statistically analyzed (ANOVA, Tukey’s test, graphs), as noise-resilient spectral indices, sensible to different plant features of interest. Their broadband versions, based on the Landsat 8 OLI and Sentinel 2 MSI satellite sensors, were also evaluated in perspective of operative and extensive remote crop monitoring from space. The results highlighted significant differences in some spectral index responses, related to different cardoon genotypes and water salt concentration. The biometric data supported by red-edge indices modelling evidenced the impact of the highest salt water concentration (200 mM/L) on the plant growth and yield.
Highlights
IntroductionTheir relevant features are high biomass production, high calorific value, low agronomic requirements, low cost of production, and fertilizer needs [6]
In the perspective of exploitation increase in renewable energies [1,2], various productive crops are currently considered as bioenergy resources capable of supporting reduction in the world’s dependence on fossil fuels and decrease in gas emissions, as already required in Kyoto agreement [3,4,5].Resources 2020, 9, 124; doi:10.3390/resources9100124 www.mdpi.com/journal/resourcesTheir relevant features are high biomass production, high calorific value, low agronomic requirements, low cost of production, and fertilizer needs [6]
Cardoon exploitation as a bioenergy resource is widely diffusing, in the Mediterranean basin, due to its relevant annual biomass yield with a low request of inputs and a significant resilience to stresses due to drought and water shortage, soil/water salinization, and soil pollution. This crop may have a wide range of bio-industrial applications and fit into different intensive cultivation strategies that can be improved by precision farming approaches, supported by the currently available remote and proximal sensing techniques, including those exploiting EO data continuously provided by orbiting satellites
Summary
Their relevant features are high biomass production, high calorific value, low agronomic requirements, low cost of production, and fertilizer needs [6]. Some bioenergy crops are suitable for cultivation, especially in marginal lands affected by industrial contamination or salinization, without irrigation to avoid rise in production costs. In this context, cardoon has been found as a low-input annual crop tolerant to drought and various environmental and climate stresses and well-adapted to be exploited as bioenergy crop in the Mediterranean areas [7,8]. Exploitation of the most performing cardoon genotypes in terms of stress tolerance, water deficit, and salinization resilience, with maximization of biomass production and other valuable production outcomes, was the goal of various research [9]
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