Kenaf: A Multi-Purpose Crop for Several Industrial Applications by Andrea Monti & Efthimia Alexopoulou

Author:Andrea Monti & Efthimia Alexopoulou
Language: eng
Format: epub
Publisher: Springer London, London

5.5 Use of Resources

Kenaf has shown good potential as a low input alternative agricultural crop (Alexopoulou et al. 2009). The N fertilizer requirements of this crop are low by comparison with other energy crops, as mentioned in the previous sections. Since synthesis of nitrogen fertilizers are energy demanding, the low kenaf N requirements, equivalent to those reported for perennial lignocellulosic crops (Fernando et al. 2010b), consequently represent low energy input needs associated with. Regarding P and K fertilizers they are usually extracted from mineral ores, which are limited. Hence, lower P and K requirements implicate ore conservation and energy savings to mine them. Average P and K fertilizer inputs, expressed as Keq, for the cultivation of kenaf in Europe were quantified and compared with the P and K fertilizer inputs of other energy crops reported in Fernando et al. (2010b). Results of this comparison indicates that the exhaustion of mineral ores associated with the P and K fertilization of the kenaf fields (226 kg Keq ha−1), is below the average observed for the cultivation of 15 energy crops in Europe (262 kg Keq ha−1), comparable to hemp fertilization (222 kg Keq ha−1), slightly higher than flax fertilization (173 kg Keq ha−1), but much lower than PK use intensities associated with sweet sorghum (583 kg Keq ha−1) and potato (757 kg Keq ha−1) crops. Being less input intensive, kenaf also generate less waste in the form of pesticide and fertilizer disposed packages, by comparison with other more demanding crops.

On the other hand, the specific water requirements of kenaf (300–400 mm of water, Alexopoulou et al. 2009) could be a limiting factor which might contribute to groundwater depletion. Effects of increased water abstraction include salinization and water contamination, loss of wetlands, and the disappearance of habitats through the creation of dams and reservoirs and the drying-out of rivers (EEA 2006). Irrigation also penalizes the energy balance. These aspects are of particularly importance in southern Europe, where in summer the soil water content is less than the specific water requirements of the crop.

Kenaf is described as opportunistic in relation to water availability, with a high rate of stomatal conductance and transpiration rate when water is not limited, and a markedly reduced stomatal conductance and transpiration rate when water availability is restricted (Patanè and Sortino 2010). Moreover, the crop tolerates drought (Bañuelos et al. 2002) and is able to recover following re-watering (Muchow 1992). Additionally, timeliness of water availability is not as critical for kenaf, which is a vegetative crop, as it is for the predominant grain crops, wheat and grain sorghum that require water at pollination and grain-filling (Ogbonnaya et al. 1998). Impacts on water use by kenaf cultivation may also be minimized due to the high cellulose content of this biomass, which allows the plant to stand upright at low water contents, as it was referred to herbaceous perennials (Lewandowski et al. 2003) and due to high water use efficiency, owed by their deep and well-developed root system (Lauriault e Puppala 2009).

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