Analyzing unexploitable, agronomic, and non-agronomic yield gaps in irrigated barley growing areas of arid and frost-prone regions from Iran

Barley (Hordeum vulgare L.) is one of the most important staple crops grown to produce feed for animals worldwide as well as in Iran with considerable surface in the arid and frost-prone climates. The yield gap analysis is an important topic for researchers worldwide as it aims to identify the factors influencing the gap between actual and potential yields and to enhance food security. To date, almost no long-term assessments have been focused on the barley yield gap analysis for the arid and semi-arid environments, particularly categorizing yield gap. In the current study, we therefore calibrated the APSIM-Barley model for three irrigated barley cultivars, validated the model using 31 field experiment reports, and applied it to simulate long-term (1989 to 2019) yields under eight production levels in eight major barley growing locations of Iran (Arak, Hamedan, Kabudarahang, Marvdasht, Neyshabour, Sabzevar, Saveh, and Shiraz). This is the first time that barley yield gaps are categorized into unexploitable, agronomic, and non-agronomic ones in Iran. The results revealed a huge difference between potential and actual yields (on average, 5.4 t ha⁻¹ yield gap) across the studied locations indicating that the farmers could achieve only 38.6% of the potential yield. Yield gap values varied over locations and seasons. Unexploitable, agronomic, and non-agronomic yield gaps in the studied locations averaged 26.7%, 55.9%, and 17.4% of total yield gap, respectively. The major part of the agronomic yield gap in the studied locations was owing to water limitation, which accounted for ~ 40% of the agronomic yield gap, followed by other agronomic (30%), frost-limited (15.8%), cultivar-limited (13.7%), and sowing date-limited (10.4%) yield gaps. Our findings showed that by improving agronomic management practices, particularly water management and farmers’ non-agronomic conditions, the current yield gaps could be reduced considerably in arid and frost-affected locations.