Determining water requirements of biblical hyssop using an ET-based drip irrigation system

Biblical Hyssop (Marjorana syriaca) is a perennial herb having high commercial and medicinal uses, with little known about its water and nitrogen requirements. The aim of this research was to investigate the effect of different irrigation regimes and nitrogen doses on the morphometric characteristics (shoot height and weight), crop yield, and water productivity of Marjorana syriaca. Growth parameters and soil water use of the crop were monitored in a randomized split-plot two-year (2014-2015) field experiment under four irrigation regimes (60%, 80%, 100%, and 120% of crop evapotranspiration − ET) and four nitrogen treatments (0, 75, 150, and 225 kg ha−1) using an automated ET- based drip irrigation system in a semi-arid climate. The results showed that Marjorana syriaca adapted best to the higher irrigation regimes, with fresh weight and dry leaf weight higher by 185% and 165% respectively than the lowest irrigation treatment. Although applying medium doses of nitrogen improved yield at higher irrigation regimes, it did not affect the harvest index or crop water productivity. Dry matter fraction (ratio of dry to fresh aboveground biomass) and to a higher extent crop water productivity (ratio of marketable dry yield to unit of water used) significantly decreased when irrigation was doubled. Biblical hyssop can be grown and perform best when irrigated with 100% fraction of evapotranspiration at full stage and when supplied with 150 kg N ha−1 yr−1.In case of water shortage, managed deficit irrigation at 60% ET increased water productivity, sustained yield, and saved water.