JOURNAL OF WATER AND SOIL RESOURCES CONSERVATION
Year:2012 | Volume:1 | Issue:2|Papers Count:7

Field capacity (FC) is one of the important parameters of soil-water-crop-atmosphere models which the accurate measurement of this parameter is very expensive and time consuming. In this study the sensitivity of the CSM-CERES-Maize model to FC for simulating soil nitrate and ammonium concentration in different soil layers, and plant N uptake was evaluated. The study was performed using the experimental data obtained from the field study conducted on silage maize in 2003 and 2004 at south Tehran, Iran. The treatments were consisted of four irrigation levels (0.7, 0.85, 1 and 1.13 soil moisture depletion) with three fertilizer levels (0, 150, and 200 kg N ha-1). The results indicated that the change of simulated soil nitrate concentration was between 7.17 and 96.75 due to 25% changes in FC (either increase or decrease). This value for simulated soil ammonium concentration was between 33.31 and 139.01. The CERES model was sensitive to FC changes in simulation of soil nitrate and ammonium concentrations and its sensitivity was different in soil layers. This model was less sensitive to FC changes in simulating mineralization, nitrification, and plant N concentration. It can be then calculated that an exact determination of FC can reduce uncertainty in simulating soil nitrate and ammonium concentrations using the CERES model.

Particle size distribution (PSD) and aggregate stability are two physical properties are important for soil conservation. This study investigates the effect of using different organic matters on the PSD in the wet and dry conditions. The experiment was conducted in randomized complete design with two plant residue treatments namely (straw stubble and pistachio residue) and three moisture levels namely 0, 1 and 5% water by weight in three replications. In addition, soil PSD was measured in two manners, dry (DPSD) and wet (WPSD). The results showed that the above treatments had different influences on the PSD, depending on the type and amounts of added plant residue and large aggregates used. For the DPSD, median sizes of aggregates in control, straw stubble (1%w), pistachio residue (1%w), straw stubble (5%w) and pistachio residue (5%w) were 0.228, 0.250, 0.227, 0.394 and 0.294 mm, respectively. In comparison to the results of DPSD relative to wet most frequent practices shifted from 0.125-0.25 mm particles to smaller than 0.125 mm. This finding indicated that the DPSD and WPSD do not follow the same trend. In addition, study of the WPSD indicated that addition of organic matters, aggregation improved and as a result larger aggregates were formed. It was also determined that application of different organic residues resulted in different amount of aggregation so that this effect was more pronounced in some sizes of aggregates.

Soil strength and elasticity modules are important parameters in the engineering characteristics of soils. Bearing capacity is increased by soil strength. Elasticity module determines the potential of soil deformation. In this experiment, stabilization of problematic clay soils using sands were investigated. The samples were prepared with variable soil moisture and compaction, and were tested in single-axis compression apparatus in the soil mechanics laboratory of Shahid Chamran University (SCU) in Khuzistan province. The samples were tested with soil moistures as follows: optimum humidity, 2% and 4% less than optimum, and 2% and 4% more than optimum moisture. The compaction of applied, R.C, were equal to 85, 95 and 100 percents. Using the obtained data, the soil strength and elasticity modules were calculated. Our findings show that for all in clay and sandy-clay samples tested increasing moisture lead to decrease of soil strength. However, reduction of soil strength in the sandyclay sample is more than problematic clay soils samples. Results of these experiments regarding the moisture change from 4% less than optimum to 4% more than optimum, decreased soil strength of problematic clay soil, approximate 84%, while, for sandy-clay soil it was about 93 percents. Moreover, decreasing of elasticity module in sandy clay samples with 100% compaction and 13% moisture is approximately 51 percents.

Conservation of good quality water is an important challenge in arid and semi-arid regions. The objectives of this study were to determine the most sensitive growing stage to drought stress and to estimate yield reaction coefficient during water shortage period and water use efficiency. An experiment with complete randomized block scheme by 3 repetitions and 7 water treatment was established for JK cultivar of soybean in spring cultivation. Water deficit treatments in different growing stages were consisted of irrigation in full growing period (Control Treatment), irrigation with moisture stress in vegetative stage, irrigation with water stress in flowering stage, irrigation with moisture stress in grain filling stage, irrigation with moisture stress in vegetative stage and flowering stage, irrigation with moisture stress in vegetative stage and grain filling stage, irrigation with moisture stress in flowering stage and grain filling stage. The obtained results indicated that flowering stage is the most sensitive stage for soybean growing period in Mazandaran Province. In irrigation with water stress in vegetative stage, water consumption was reduced 28 percent, while 4 percent reduction of yield was observed. Irrigation with moisture stress in vegetative stage also had Maximum water use efficiency.

One of the most important parameters for design of hydraulic constructions is standard project storm which is derived from IDF curves for specific durations and return periods. The previous methods to estimate IDF curves are time consuming. In addition, they required many input parameters that tend to reduce their reliability. In previous methods, rainfall data should be recorded in different durations to extract the IDF curves. In some regions, only 24-hour rainfall data are recorded that they cannot build the IDF curves. In this study, temporal scaling properties of rainfall were used to extract the IDF curves for short durations from daily rainfall data. The used method has less complex stages and less number of parameters compares to previous methods. The proposed method was used in Saveh hydro-meteorological station as a case study and the results indicated its reasonable accuracy.

Abundance of amounts of fluoride in water resources has a harmful effect on human health. A new magnetic nanoadsorbent was developed by treating Fe3O4 nanoparticles with 3- aminopropyltriethoxysilane and Nb (V) - metalloporphyrin and applied to remove excessive fluoride from aqueous solutions. Nb (V) - metalloporphyrin was attached to Fe3O4 via the interaction between the carboxylic groups and the amine groups of APTES. Fourier Transform Infrared Spectroscopy (FTIR), elemental analysis, X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) were used to characterize the synthesized nanoparticles. The effect of pH, contact time, sorbent dosage and some co-existing anions present in aqueous solution was investigated. The results indicated that under optimal conditions (i.e. pH: 5.5, contact time: 30 min and sorbent dosage: 100 mg) the fluoride removal efficiency of 94.0% can be achieved. Regeneration of fluoride adsorbed material could be possible with NaOH and the modified magnetic nanoparticles exhibited good reusability for four cycles.

Geostatistical methods are one of the most advanced techniques for monitoring of groundwater quality. In this research, we compare efficiency of three interpolation techniques namely IDW, kriging, and cokriging for predicting a few groundwater quality indices such as: Na+, TH, EC, SAR, Cl-, Ca2+, Mg2+ and SO4. Data were gathered from 75 wells in Darab district, of Fars province. After normalizing the data, variograms were computed. A suitable model of fitness on experimental variogram was selected which was based on least RMSE value. Then the best method for interpolation was selected, using cross-validation and RMSE. Results showed that for all groundwater quality indices, cokriging performed better than other methods in simulating groundwater quality indices. Finally, using cokriging method, maps of Groundwater quality were prepared in GIS environment.