Berseem clover quality and basil essential oil yield in intercropping system under limited irrigation treatments with surfactant

• Surfactant efficiency on berseem clover quality was tested in arid/semiarid regions.
• Additive intercropping treatments improved all berseem clover’s quality traits.
• Basil essential oil yield was significantly improved by the surfactant application.
• The highest essential oil yield in basil was obtained from the I75 + surfactant setup.
• The essential oil yield of basil was enhanced in the deficit irrigation treatments.

The presented study is a comprehensive report on the qualitative configuration of crop quality, essential oil percentage and oil yield in berseem clover and basil under limited irrigation and additive intercropping systems using a nonionic surfactant. This experimental field study was conducted in the 2012–2014 growing seasons to identify the best combination of irrigation level, sowing pattern and water treatment for basil oil content and yield, and berseem clover with an acceptable forage quality for arid and semi-arid regions. The limited irrigation treatments comprised of full irrigation, I100 (100%), moderately limited, I75 (75%), and severely limited, I50 (50%). The planting systems of sole berseem clover and sole basil culture, along with the additive intercropping of berseem clover and 50% basil, were assigned to the plots under water treatment alone (control) and water with surfactant setups. Results show that, as the severity of drought stress increased (I50), dry matter digestibility of berseem clover in I50 with surfactant decreased moderately when compared to I50 irrigation alone. Crude protein, water-soluble carbohydrates and neutral detergent fiber percentages followed increasing trends in limited irrigation systems in water treatments both with and without surfactant. All forage quality traits of berseem clover were improved in the additive intercropping treatment (legume–basil mixture). Application of surfactant was favorable to a sole basil culture, enhancing the essential oil percentage as well as oil yield under a deficit irrigation treatment. The highest essential oil yield (11.45 kg ha−1) was achieved in the I75 with surfactant treatment. Additionally, the basil essential oil yield increased during sole cropping in comparison with the mixed cropping system. The water use efficiency in the intercropping system across surfactants in arid and semi-arid regions was improved during the warm season when soil water availability decreased due to the high temperature and low precipitation.