Water and nitrogen balance of sweet sorghum (Sorghum bicolor moench (L.)) cv. Keller under semi-arid conditions

In the framework of the E.U. project Fair CT 96-1913 "Environmental studies on sweet and fibre sorghum, sustainable crops for biomass and energy", a research has been carried out with the aim to study the water and nitrogen balance and determine the critical N dilution curve of sweet sorghum cv. Keller. A field experiment was performed, where three irrigation treatments (I-0 = dry control, I-50 = 50% ETm restoration, I-100 = 100% ETm restoration) and four nitrogen fertilization levels (N-0 = no nitrogen control, N-60 = 60 kg z, N-120 = 120 kg ha(-1); N-180 = 180 kg ha(-1)) were studied. The final yield was significantly affected by the amount of water distributed but not by the nitrogen level. The treatments watered up to crop establishment (I-0) produced, in the average, 7.5 t ha(-1) of dry matter, against 21.1 and 27.1 t ha(-1) of I-50 and I-100. respectively. The crop determined a great reduction in nitrate concentration of soil water, irrespective of nitrogen supplied. The variation between N output and input (Delta) was negative in N-0, N-60 and N-120 and positive in N-180. The critical value of nitrogen uptake change in relation to the water availability. The amount of nitrogen supplied did not determine significant differences upon WUE. The crop seems to have a great potentiality in Mediterranean environment in terms of yield production.