Limited water supply on fibre sorghum (Sorgum bicolor L. Moench) in central Italy

The availability of new sorghum hybrids for the production of fibre paves the way for the production of large amounts of fibre from crops with limited agrotechnical requirements. A 3-year trial was carried out in two locations in Central Italy (Perugia and Rome) to assess the effects of limited water supply on fibre sorghum yield. Four sorghum hybrids were compared using different irrigation treatments based on two criteria: 1) replacement of 33%, 66% and, only at Perugia, 100% of crop evapotranspiration; 2) restoration of field capacity at given stages of crop cycle: two irrigations (the first occurring when 10-12 leaves had unfolded and the second twenty-thirty days later); one irrigation (when 13-14 leaves had unfolded). At Perugia two irrigations (F2) were sufficient to reach about 16 t ha*[-1) of stems + sheats dry matter. A66 treatment, comparable with F2 for total irrigation volumes, produced slightly higher yields (17 t ha*[-1)), but requiring a higher number of applications. The F1 treatment, with 14.7 t ha*[-1), was found to produce statistically lower values than F2 and similar to A33 (14.3 t ha*[-1)). At Rome, with a single irrigation of 900-1,000 cube m ha*[-1) (F1) the yield was on average 21.5 t ha*[-1); a second water application (F2) brought about small yield increases. The 66% replacement of ETc did not entail an increase in yield compared with F1 and F2 treatment, even though the total amount of water or the number of applications were higher. The results obtained, albeit with different yield potentials, have shown that the sorghum hybrids yields are particularly interesting especially as regards the reduction of irrigation water, thus confirming that also these new hybrids of fibre sorghum respond well to limited water supply