The Water use Efficiency for Different Varieties of Wheat and the Effect of Supplemental Irrigation in the Semi-Arid Regions of Tunisia

This work was recorded during the year 2008/2009 within thepublic farm ofagricultural machinery training center in Siliana-Tunisia (AMTCS) that belongs to the irrigated district of Lakhmess covering an area of 1275 ha. Cereals are the most practicedcrops representing 49% of the total cultivated area within the irrigated district. Themain objective of the study is to determine the water use efficiency for different wheat cultivars and to analyze the impacts of supplemental irrigation on cultivars yields.Five cultivars of durum wheat (Karim, Khiar, Razeg, Nasr, Oumrabii) andfour cultivars of soft wheat (Birsa, Vaga, Utique, Hidra) were cultivated in the public farm and one cultivar of durum wheat (Khiar) was cultivated within a private farmbelonging to the same region. The area was divided into 9 strips (100 m x 20 m). These different varieties were conducted under rain fed and in supplemental irrigation conditions. An amount of 100 mm of irrigation water was provided in the plot of the AMTCS as follows: 50 mm in seedling stage (December16th, 2008), 50 mm in the fulltillering stage (March10th, 2009). In the plot of the private farm, 150 mm of irrigation water was distributed as following: 50 mm in the seeding stage (10 December 2008), 50 mm in full tillering stage (10 March 2009), 50 mm in grain filling stage (May 2nd, 2009). The sprinkler irrigation was used with a spacing of 12m x 12 m and the plots were irrigated by a hydrant irrigation existing in each plot.The flowwas 5 l/s supplied from Lakhmess dam with a salinity of 0.5 g/l. The sprinkler rainfall was 8.5 mm/h with a uniformity coefficient of 92 %.The model CropWat was used to determine the water requirements of wheat. Grain yield was determined by multiplying the density of cobs by the number of grain per cobs and the Mile grains weight (g). The water use efficiency is the ratio of the grain yields and the amount of water consumed. Under rainfed conditions: The average of water use efficiency was 0.38, 0.36 kg/m3respectivlyfor durum and soft wheat. Under irrigated conditions, the best efficiencies of durum wheat were obtained by Khiar, Razeg and Nasrwith an average of 1 kg/m3.For soft wheat the varieties Vaga and Utique had the best efficiencies of 1.14 Kg/m3.In the private farm, the water use efficiency of the variety Khiar used was only 0.95 Kg/m3. The effect of supplemental irrigation was remarkable. In fact, it improved theyields for all varieties of durum and soft wheat respectively by 397% and 347 %.