Most of soils of Iran are calcareous in nature.High pH and carbonate levels are common characteristics of these soils.In these conditions the heavy metals tend to occur in insoluble forms,mainly precipitates as carbonates or oxides.The heavy metal Pb contaminates soils,plants,water,the atmosphere,animals and humans,especially in areas of heavy traffic.This experiment was conducted to find the relationship between the Pb adsorption and selected properties of calcareous soils. Twenty surface (0-20 cm) soil samples with pH ranging from 7.6 to 8.2 and calcium carbonate equivalent (CCE) ranging from 27 to 64% were used in the Pb adsorption study. Two-gram subsamples of each soil were equilibrated with 50 mL of 0.01 M KNO3 solution initially containing 30,000 to 300,000 mg Pb L -1 . The Pb that disappeared from solution (after 2 h shaking at 25oc) was considered as adsorbed Pb. The adsorption data showed a highly significant fit to Freundlich and Langmuir adsorption isotherm. The coeficients of both isotherms showed significant positive correlations with CCE, OM and clay, except for A Freundlich and OM for which the correlation is negative. Distribution coefficient (also called maximum buffering capacity) calculated as the product of Langmuir K and b, was also found to be significantly related to CCE and OM.

Water research studies in Saudi Arabia clearly showed sever depletion of groundwater. Therefore, the scientifically applied research program related to water saving and conservation in agriculture is essential, where agricultural activities account for more than 85% of the total water consumed. This study aims to investigate the effect of four irrigation levels, two irrigation methods and three clay deposits on water use efficiency (WUE) of squash and the distributions of salts and roots in sandy calcareous soils. A field experiment was conducted at the college experimental station in 2002 and 2003 seasons. It consists of three clay deposits, three rates (CO=0, C2 = 1.0 and C3 = 2.0%), four irrigation levels (T1 = 60, T2 = 80, T3 = 100 and T4 = 120 % of Eto) using surface (IM1) and subsurface (IM2) drip irrigation. Results indicated that squash fruit yield was significantly increased with the increase in irrigation water level for each season. Generally, WUE values were increased as linearly with applied irrigation water and decreased at the highest irrigation level. Types of clay deposits significantly affected fruit yields compared with the control. The yield increase was 12.8, 8.35 and 6.4% for Khulays, Dhruma and Rawdat clay deposits, respectively. The differences between surface and subsurface drip on fruit yields and WUE were also significant. Results indicated that moisture content of subsurface treated layer increased dramatically, while salts were accumulated at the surface and away from the emitters in subsurface drip irrigation. Intensive root proliferation is observed in the clay amended subsurface layer compared with non amended soil. The advantages of subsurface drip irrigation were related to the relative decrease in salt accumulation in the root

Summary: Water and energy balances of sprinkler irrigated winter wheat were measured at Bushland, TX over the 1989-90, 1991-92, and 1992-93 seasons. Water balances were measured using weighing lysimeters. Net radiation and soil heat flux were measured at each lysimeter and solar radiation, wind speed, air temperature and dew point temperature were measured at a nearby weather station over grass. The ENWATBAL model was used to predict evapotranspiration (ET), net radiation (Rn), and soil heat flux (G). These were compared to daily measured values with good results. Coefficients of determination (r ) ranged from 0.92 to 0.97 for linear regressions of estimated vs. 2 measured ET; from 0.81 to 0.96 for Rn; and from 0.61 to 0.83 for G. The model underpredicted H and ET under windy conditions for a tall crop. Needed model improvements include a mechanism for including crop height in calculations of sensible and latent heat fluxes, and modifications for freezing conditions.