Knowledge aboutbiomass partitioning of maize grown in arid and semi-arid climatesis scarceand yet essential to select a robust and effective deficit irrigation management (DIM) strategy for these regions.The objectives of this study were to: i)investigate the effects of different levels of water application under two DIM strategies on the root and aboveground characteristics, the response factor to water stress (K y) and irrigation water use efficiency (IWUE) of silage maize at different growth stages, andii) determine the best DIM strategythat 44 would maximize biomass productivity.Field pot experimentswere conducted in Isfahan, 45 Iran,during 2009 and 2010.The twoDIM strategies werefixed irrigation interval-variable 46 irrigation depth (M 1), and variable irrigation interval-fixed irrigation depth (M 2).Each DIM strategy was tested at four water-deficit levels, including: severe, moderate, mild,and a fullirrigation.In M 1 , irrigation intervals were consistent for all irrigation treatmentsbut were varied over the growing season. Treatment effects weremeasured at the10-leaf, 16-leaf, tasseling, milk,and silage harvestcrop growth stages.There was significant effect of irrigation and growth stage on total aboveground biomass (TB), leaf area (LA), root biomass (RB), and root:shoot ratio (RSR)for both DIM strategies during the two years.For M 2 , there was 53 significant difference in TB, LA, RB, and RSR between all irrigation levels at all growth 54 stages.TB production was on the average around 25% higher for M 1 compared to M 2 , even 55 though total applied irrigation water was only 6% higher for M 1 .Comparing the two DIMsshowed that RSR and K y wereboth higherforM 2 , indicating that the crop was more sensitive to this strategy.In conclusion, M 1 was selected as the best management practicesince it had more favorable effects on improving the IWUE and also on the development of maize rootsduring the growing season.

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A simple analytical method was developed for directly calculating the thermodynamic wet-bulb temperature from air temperature and the vapor pressure (or relative humidity) at elevations up to 4500 m above MSL was developed. This methodology was based on the fact that the wet-bulb temperature can be closely approximated by a second-order polynomial in both the positive and negative ranges in ambient air temperature. The method in this study builds upon this understanding and provides results for the negative range of air temperatures (2178 to 08C), so that the maximum observed error in this area is equal to or smaller than 20.178C. For temperatures $08C, wet-bulb temperature accuracy was 60.658C, and larger errors corresponded to very high temperatures (T a $ 398C) and/or very high or low relative humidities (5% , RH , 10% or RH . 98%). The mean absolute error and the root-mean-square error were 0.158 and 0.28C, respectively.

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