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The specific surface area of soil (SSA) is crucial for the interaction of ions and water molecules with the soil particles. Therefore, many physical and chemical properties of soil are determined by its total specific surface area. Measurement of SSA is time-consuming and laborious; therefore, its estimation by a physical or an empirical model is preferred. The objectives of this investigation were: (i) To estimate the SSA of soils from the south of the Islamic Republic (IR) of Iran by considering spherical and cylindrical models for soil particles (physical model), and (ii) to develop a multivariate pedo-transfer function to estimate SSA based on the geometric mean (d g ) and the standard deviation (s g ) of the diameter of soil particles (empirical model). The results indicate that the physical model is superior to the multivariate pedo-transfer function in estimation of SSA. However, a power pedo-transfer function for d g ðSSA ¼ 3:89 d g À0:905 ; SSA in m 2 g À1 ; d g in mmÞ is superior to the physical model and the multivariate pedo-transfer function for the estimation of SSA.

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The present study was conducted to investigate the relational effects of various sowing dates and deficit irrigation on grain yield, protein and yield components of barley, in a semi-arid region (southern part of Iran) during growing seasons 2011-2012 and 2012-2013. A Split plot layout within a randomized complete block design with three replications was used. Main plots were selected as Irrigation treatments with varying water irrigation levels consisting of: (1) full irrigation, FI, (2) 0.75 FI, (3) 0.5 FI and (4) Dry land (rain-fed) during both growing seasons. Sub plots were the sowing dates consisted of: (1) 23 th October (T1), (2) 6 th and (3) 22 th November (T2 and T3) and (4) 6 th December (T4). The interaction of different irrigation levels and sowing dates had a significant impact (p<0.05) on grain yield, grain and straw protein, 1000-grain weight, plant height, biomass, water use efficiency (WUE), and crop evapotranspiration. Results revealed that the largest amount of protein was obtained in the latest sowing date (T4) at dry land treatment in two consecutive years. Full irrigation treatment showed the largest rate of dry matter accumulation (14.72 and 15.25 Mg.h -1 for the first and second years, respectively), while the smallest rate was seen in the rain fed treatment (4.22 and 7.43 Mg.h -1 for the first and second years, respectively). The largest yield was obtained with the 23 th October (T1) sowing date in full irrigation treatments (FI). The largest water use efficiency was achieved with 0.5FI and the earliest sowing date (T1).

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