Growth indices of winter wheat as affected by irrigation regimes under Iran conditions

An experiment was conducted during 2004-2006 at the Agricultural Research Station, Islamic Azad University, Khorasgan Branch, Isfahan, Iran. The purpose of this study was to evaluate the effects of irrigation regimes on growth indices of three bread wheat (Triticum aestivum L.) genotypes. A split plot layout with a randomized complete block design with four replications was used. Irrigation treatments (irrigation after 70 (I1), 90 (I2) and 110 (I3) mm cumulative evaporation from class A evaporation pan) were considered as the main plot and three wheat genotypes (Mahdavy, Ghods and Roshan-Backcross) as subplots. The I1 and I2 did not differ significantly for all growth indices, total dry matter and grain yield. Delay in irrigation from the I2 to I3 significantly reduced growth indices, total dry matter and grain yield. Trend of changes in Leaf Area Index (LAI), Total Dry Matter (TDM), Net Assimilation Rate (NAR) and Crop Growth Rate (CGR) were similar in the I1 and the I2. In all samplings, delay in irrigation from the I2 to I3 reduced all growth indices. The trend of changes in crop growth rate was more similar to leaf area index, than to net assimilation rate. Genotypes were not significantly different in respect to growth indices. The results indicate that irrigation after 90 mm cumulative evaporation from class A evaporation pan might be suitable for winter wheat production under conditions similar to this experiment where irrigation water during spring is not abundant.