Abstract
A large interest is currently addressed to the no-food crops as an alternative source of energy. One of these crops is the biomass sorghum (Sorghum bicolor L. Moench) thanks to its high biomass productivity and high use efficiency of solar radiation and water. Aim of the research is assess the biomass sorghum response to the water in the Mediterranean environment. Biomass sorghum was subjected to four irrigation regimes, at 50, 75, 100 and 125% of ETc for three years (2008, 2009 and 2010). Water use efficiency (WUE), irrigation water use efficiency (IWUE) and water stress index (WSI) were calculated. Plant dry matter and green area index resulted different among the three years and the differences among irrigation treatments were more evident in 2009. The different soil water content at sowing among the three experimental years, affected the growth path during the growing crop cycle, explaining differences in term of biomass accumulation, leaf expansion and water consumption. WUE was higher in 2009 than in 2008 and 2010 with no differences among irrigation treatments for the first and third experimental year. WU ranged between 891 and 566 mm, the aboveground dry matter biomass between 4097 and 1825 g m-2 and WUE between 8.49 and 4.00 kg m-3. IWUE, similarly to WUE, was higher in the second year than in the first and third year, but with differences among irrigation treatments in the 2008 and 2010. WUE calculated from WU normalized with VPD gave a more stable parameter in the three years. This research showed the suitability of biomass sorghum as energy crop in Mediterranean environment and its ability to use water efficiently.
Highlights
In the Mediterranean environment, where rainfall occurs mainly in winter, water is the crop yield limiting factor, especially for summer crops such as sorghum
The maximum (Tmax) and minimum (Tmin) temperatures were different over the three years from the first part of growing cycle
May 2009 was characterized by Tmax and Tmin greater than those of 2008 and 2010, with Tmax characterized by values greater than 10°C compared with long term averages
Summary
In the Mediterranean environment, where rainfall occurs mainly in winter, water is the crop yield limiting factor, especially for summer crops such as sorghum. An inadequate water supply in sorghum can reduce the efficiency in the conversion of the intercepted radiation in dry biomass even though the solar radiation is an abundant factor in Mediterranean areas (Dercas & Liakatas, 2007; Garofalo et al, 2011; Rinaldi & Garofalo, 2011). Turner (1974) highlighted that soil water deficit reduced the stomatal conductance, transpiration, photosynthetic rate and dry matter accumulation. Rosenthal et al (1987) reported adverse effects on some crop variables such as leaf area, stem height and biomass production, with soil water decrements
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