Yield gap analysis in major wheat growing areas of Khorasan province, Iran, through crop modelling

To increase wheat productivity from current levels, the yield gap, the difference between actual and potential yield, should be analyzed. A crop model was calibrated for three winter wheat cultivars and validated for a major wheat growing area to evaluate yield gaps in Khorasan province in northeastern Iran. The validated model was used to simulate long-term yield for 14 locations under three management conditions (potential, water-limited, nitrogen-limited). The results showed that the average simulated potential yield of 7.8 Mg ha−1 has not yet been realized by farmers and there is a large gap between the actual and potential production levels (about 5.2 Mg ha−1). The simulation showed considerable difference between cultivars for yield gap. When averaged over locations and seasons, the total yield gap obtained for Chamran wheat was 4.4 Mg ha−1, for Sionz was 6 Mg ha−1, and for Gascozhen was 6.1 Mg ha−1. Across locations, the proportion of yield gap from water-limitation was 1.7% to 19.5% and for nitrogen- limitation was 40% to 47%. The gap caused by other limiting and reducing factors was 33-57%. The highest yield gap was observed in Ghaen for Gascozhen (7.6 Mg ha−1) and the lowest was observed in Sarakhs for Chamran (3.1 Mg ha−1). The results of the study suggest that the average farm yield of about 2.6 Mg ha−1 in irrigated fields in Khorasan province is not limited by low genetic yield potential. This indicates that farmers should emphasize more on management factors such as water availability, timing of nitrogen application, and selection of cultivars adapted for each environment to reduce yield gap.