Assessment of Effective Factors on Duration of Rainfed Barley Phenological Stages in Semi-Arid Climate Using Principal Component Analysis

Due to the water shotages in arid and semi-arid climates, rainfed agriculture faces severe challenges. It is therefore essential to carry out specific studies on the efficiency factors of rain-fed crop growth. The purpose of this study was to assess the factors affecting the duration of the different phenological stages of rain-fed barley in a semi-arid region. For this purpose, duration of phenological stages for five different growth periods of rain-fed barley including sowing-emerge, emerge-tillering, tillering-stem, stem-flowering, and flowering-maturity were extracted at the Sararoud station, Kermanshah, during the period of 2000-2015.  By calculating 12 variables for these periods, the variables with significant impacts were detected for each of them and Principal Component Analysis (PCA) technique was used to assess the impact of these variables on different phenological stages duration. The results showed that between different selected variables, the degree-days-based variables (GDD and PTU) and absorb radiation-based (net radiation and daily mean soil surface temperature) showed the highest impact on all of the phenological stages duration. Each of the evapotranspiration-based variables, soil moisture supply variables and complementary variables influenced duration of two growth stages. The highest variability of the different growth periods which explained by the selected variables in the current research using principal component analysis was obtained for sowing-emerge stage. The overall results showed that the principal component analysis not only has a high capability to detecting effective factors on the different phenological stages duration, but also is a powerful tool to regulate the interrelate impacts between variables..