Direct Seeding Under Plant Cover: Effects on the Agronomic Performances and Water Use Efficiency of Durum Wheat Crop in a Semi-arid Region

Water is the most limiting factor of crop production in semi-arid areas. In this way, Conservation Agriculture (CA) based on direct seeding has been proposed as a promising strategy for improving soil quality and water use. As part of the CA-Maghreb project, a field experiment was carried out during the 2017–2018 crop-ping season in the El-Krib region of North-Western Tunisia. The experiment studied the agronomic performances and water use efficiency (WUE) of two durum wheat cultivars (“Maali” and “Hadhba”), conducted in direct seeding under living plant cover (DSLC) and direct seeding under dead plant cover (DSDC). Results showed that the “Hadhba” cultivar recorded the highest cumulative total dry matter rate when grown in DSLC, with 1.04 kg m−2 compared to the “Maali” variety, which recorded 0.59 kg m−2. The highest grain yields were obtained when durum wheat was grown in DSDC (0.17 and 0.16 kg m−2) for “Hadhba” and “Maali”, respectively. The highest WUE was recorded for the “Hadhba” cultivar, with an improvement in WUE for dry matter production in DSLC (3.21 kg m−3) compared to sowing under dead cover (2.69 kg m−3). Based on these results, the DSLC package constitutes a potential sustainable pathway to improved water resource use and crop yields. However, direct seeding under plant cover alone is not enough to obtain higher yield productivity. Complementary practices, such as crop rotation and residue management, are required to be included to make CA systems more functional in the short and long term.