Water productivity of Origanum syriacum under different irrigation and nitrogen treatments -

Abstract

Origanum syriacum is a perennial herb from the Lamiaceae family in Lebanon. Origanum species are important culinary herbs with high commercial and medicinal potential. Origanum is native to Middle East and performs well in average dry soil, however, little is known about the species’ water requirements. The present work presents the results of a field experiment at the American University of Beirut’s (AUB) Agricultural Research and Educational Center (AREC) in addition to a greenhouse pot experiment performed to study the effects of various irrigation and nitrogen (N) treatments on the growth of Origanum which provides information on yield quantity, growth parameters and soil water use of Origanum syriacum. The field experiment included four irrigation treatments calculated to be equal to 60, 80, 100 and 120percent of Hargreaves ET) automatically set and calculated via a commercial irrigation controller and a weather station and four N treatments (0, 75, 150, 225 kg-ha). Flow meters were installed on all four irrigation treatments to measure irrigation volumes. Additionally, the greenhouse experiment also consisted of four irrigation treatments based on available water (70, 50, 30 and 10percent of managed allowable depletion) and four nitrogen treatments (0, 75, 150, 225 kg-ha). Irrigation scheduling in the greenhouse was automatically set based on soil moisture determination using soil moisture sensing devices. Two cuts were cultivated and analyzed from both the field experiment and the greenhouse experiment. Origanum water productivity, shoot height and number, fresh and dry weight, and dry leaf yield were assessed. Significant reductions were observed in above ground fresh and dry biomass and dry leaf yield with increasing water deficit. The lowest irrigation treatment in both field and greenhouse experiment was significantly different from all other treatments. Only the highest N had significant, pronounced effects on Origanum, and only during the second cut from the AREC experiment. Considering the various