Assessment of the Supplementary Irrigation Effect on Wheat (Triticum aestivum L.) Water Requirement in the Presence of Shallow Groundwater

Now, water is the most important and the most limiting factor in agricultural production sector. Certainly, different countries which located in arid and semi-arid region and are faced with water shortage must be applied specially strategies for the suitable and correct water use. In this research two-year experiments from year 2009 -2010 and 2010-2011 was conducted to find the effect of time and value of three supplementary irrigation procedure including without supplementary irrigation, once irrigation at flowering and twice irrigation at flowering and seedling stages on three wheat cultivars in the presence of constant groundwater table with 80cm depth in three replicate. Experiments performed at Razi University lysimeteric research station No1. Results showed no significant difference (P<0.05) between without and once supplementary irrigation treatment was happened. Totally, groundwater contribution under different supplementary irrigation was varied from 57.1% to 71.0% during two years of experiments for different wheat Cultivars. Also, the outcome of this study indicate that, by applying timely and optimal supplementary irrigation in the presence of a shallow water table (at a constant depth of 80 cm) in a semi-arid climate with an limited average annual rainfall, enables to compensate the total water requirement of winter wheat during the growing season. The results on this investigation showed that during wheat cultivation, existing shallow groundwater in different western, north western, north and southern parts of Iran can compensate some parts of wheat water requirement. Therefore a huge volume of surface water for wheat irrigation can be saved and more land irrigation, and job creation will be possible.