Abstract

Wheat production in semi-arid area of Tunisia is limited by low rainfall (200-400 mm year^-1), and by the irregularity of the distribution of precipitation and intensification of drought during cropping season. Therefore, irrigation is proposed as alternative to improve production and to maximize water-use efficiency (WUE) of wheat. So, rational irrigation is important for increasing crop yields and decrease water use. The objective of this study was to investigate the effects of different irrigation levels on water consumption, water use efficiency of total dry matter and water use efficiency of grain yields. The study was conducted for three consecutive cropping seasons (2005-2008). Results showed thatthe daily water consumption was varied through phonological stage. In fact, the maximum water consumption was observed at anthesis and grain filling stages. The cumulative water consumption was decreased between 3% and 37% respectively, from D1 (100% ETM) to D2 (70% ETM) and From D1 to D4 (rainfed). The relationship between total dry matter (TDM) and water consumption (WC) was in linearly regression with a high correlation coefficient (R²) witch varied from 0.89 to 0.99. The water use efficiency of total dry matter (WUE-TDM) gradually decreased when irrigation levels increased. The highest, WUE-TDM (3.24 kg/m³, 3.65 kg/m³ and 2.82 kg/m³) was recorded under rainfed condition (D4 treatment), respectively for 2005-2006, 2006-2007 and 2007-2008. On the contrary, water use efficiency of grain yield (WUE-GY) increase considerably when irrigation levels increase. In the first year of experiment, no significant difference between treatments was observed. Therefore, the moderate irrigation (D2) recorded the highest WUE-GY (1.63 kg/m³) in the second cropping season (2006-2007). In 2007-2008, D1 and D3 irrigations regimes recorded the highest WUE-GY, respectively 1.17 kg/m³ and 1.11 kg/m³. Deficit irrigation regimes (D2 and D3) were considered as rational irrigation levels to improve grain yield of wheat and to maximize WUE in the semi-arid area of Tunisia.

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