The Apulia region in Southern Italy is an important area for sugar beet cultivation. It is characterised by clay soils and a hot-arid and winter-temperate climate. The capability of sugar beet to exploit solar radiation, water use and irrigation supply in root yield, total dry matter and sucrose production was studied and analysed in relation to two experimental factors: sowing date – autumn (October–December) and spring (March) – and irrigation regime – optimal and reduced (respectively with 100 and 60% of actual evapotranspiration). Data sets from three experiments of spring sowing and three of autumn sowing were used to calculate: (1) water use efficiency in the conversion in dry matter (WUEdm, plant dry matter at harvest versus seasonal water use ratio), in sucrose (WUEsuc, sucrose yield versus seasonal water use ratio); (2) irrigation water use efficiency in the conversion in dry matter (IRRWUEdm), in sucrose (IRRWUEsuc) and fresh root yield (IRRWUEfr); and (3) radiation use efficiency (RUE, plant dry matter during the crop cycle and at harvest versus intercepted solar radiation ratio).