Growth, water and radiation use efficiency of kenaf (Hibiscus cannabinus L.) cultivated in the Mediterranean conditions

The research reported in this paper determined the relationships between growth and radiative regime of kenaf cultivated with enough water irrigation to replace all of the calculated maximum evapotranspiration. The trial was carried out during the 1996 season at Metaponto in southern Italy (lat. 40 degrees 24' N; long. 16 degrees 48' E; altitude of 8 m a.s.l.) on clayey soil. Cultivar "Tainung 2" was sown at 0.5 m spacing between rows and thinned to 40 plants m(-2). Irrigation water was applied by a localized irrigation method. During the biological cycle, the following measurements were taken: solar radiation (both incident and transmitted to the soil), photosynthetically active radiation (both incident (PARi) and transmitted to the soil (PARt): leaf area index (LAI), and dry matter accumulation. These measurements were used to determine three parameters: extinction coefficient (k) radiation use efficiency, and water use efficiency. The value of k was 0.35, while the values of radiation use efficiency and water use efficiency were 2.65 g MJ(-1) and 2.91 kg m(-3), respectively.