مجله تحقیقات آب و خاک ایران
سال چهل و یکم شماره 2 (پیاپی 5، بهمن و اسفند 1389)

The dominant traditional view to designing drainage systems explains drainage goals only in terms of crop yield increase and rhizosphere improvement while ignoring the environmental impacts of drainage projects. Nowadays, this view has been changed into a new one in which both environmental and agricultural purposes are taken into consideration. Depth and spacing of subsoil drains are important parameters in designing drainage systems, the proper determination of which can improve the system's performance. In this research, experimental and numerical Visual MODFLOW models were employed for simulation of water flow and salt transfer to pipe drains; and the effects of depth and drain spacing on quantity and quality of drain water were considered in either model. On the basis of the results obtained from the experimental model and the numerical simulation of flow for various depths and spacing of drains, a formula was presented and calibrated. Chemical characteristic indices of drain water (EC and TDS) can be determined based on this formula, considering drains depth and spacing, hydraulic head, recharge rate, and index quantities of chemical characteristics of inflow and of groundwater. This formula was validated through a comparison of computed and observed hydraulic heads for various placements positions of drains on the basis of two statistical characteristics of RSME and R2. The obtained mean values of 0.154 cm and 0.994 for these statistical indices, respectively, indicated the acceptable accuracy of the formula.

Soil drainage conditions significantly affect the chemical properties of soil, particularly type and the extent of iron oxides. Soil magnetic susceptibility (?) has a close relationship with drainage conditions. Eight soil profiles, in four regions of Fars province, with aquic and non-aquic soil moisture regimes were studied to determine the effect of drainage conditions on? and on chemical forms of Fe-oxide. A positive and significant correlation was noticed between? and Fed. Aquic soils bore distinctly lower? s than non-aquic soils (19.9 vs. 32.5). Magnetic susceptibility of surface horizons was greater than that of sub-surface horizons in most of the soils (31 vs. 19.6), which is probably a result of pedogenic formation of ferrimagnetic minerals in soil surface. Aquic and non-aquic soil lost 41 and 64 percent of their? after CBD extraction, reflecting differences in the source of? . Sequential heating of soil samples upto 550 °C resulted in more enhancement of? , in aquic soils as compared with non-aquic soils, (451% vs. 155%) which was attributed to the conversion of canted antiferromagnetic minerals to ferromagnetic ones. The value of? decreased when heated from 550 to 700 °C (about 100% in both soil groups).

Plants and soil microbes are the main sources of most enzymes available in the environment. It is, therefore, anticipated that any change in the growth of soil biota in response to salinity, may reduce the synthesis and production of extra- and intra- cellular enzymes. As a result, a reduction in the growth of plants and the activity of soil microbes in saline environments may lessen the level and the activity of soil enzymes. Soil salinity may reduce microbial growth and activity in different ways. The aim of this study was to determine the direct effects (by reducing the osmotic potential and specific ion effect) and indirect effects of salinity (by changing quality and quantity of root exudates) on soil enzymes activity. As to prove these effects, an uncultivated soil was used to determine direct effects, while soils under clover and wheat were used to determine the indirect effects, of salinity on soil enzyme activities. In the study, five levels of salinity using NaCl, CaCl2, MgCl2 and KCl; and three soil media (non-cultivated soil, soil cultivated with wheat and clover) replicated three times constituted the factorial experiment arranged in a completely randomized design. The experiment was carried out in a sandy clay soil under greenhouse conditions and lasted for 120 days. Results indicated that salinity caused significant reduction (P<0.001) in enzyme activities in uncultivated soil, as well as in the rhizosphere of clover and wheat plantations. Enzymes activities had significant correlations (P<0.05) with the root biomass of the two plants. So, one may attribute the lowered enzyme activities to the reduction in root biomass. With increasing salinity, the reduction in clover root biomass was observed to be more than that in wheat biomass, indicating more reduction in soil enzyme activities in the clover rhizosphere being largely due to less development of its root biomass in saline environment. Furthermore, the data indicated that enzyme activities in the clover and wheat rhizosphere, at high salinity levels, were almost similar to those in uncultivated soils, there being a small difference in enzyme activities observed the three media at high salinity levels, suggesting that role of indirect effects might be less pronounced with increase in soil salinity.

Secondary flow investigation could be regarded as an important issue in open channel flow, in spite of its lower quantity compared to the base flow in the water course. It should be given special consideration because of the influence on some hydraulic factors in open channel, specifically in compound channels. In compound channel's due to the difference in the flow velocity of the main channel and that of the floodplain, shear stress in inner layers of fluid increases which aid in developing secondary flow in the area. With regard to the nature of turbulent flow and shear stress, direct measurement of shear and secondary flow requires special laboratory instruments and techniques, while it has little practical importance. In this paper, by using simple available techniques, depth averaged flow characteristics were compiled and used along with two dimensional Shiono-Knight depth average model. The results indicated that the longitudinal slope does not affect the secondary flow and the eddy viscosity

To investigate the effects of Sowing Date (SD) and Single Irrigation (SI) on grain yield of rainfed wheat varieties, this experiment was conducted as split-split plot arranged in a Randomized Complete Block Design (RCBD) with three replications from Sep.2000 to Sep.2004 at the main station of Dryland Agricultural Research Institute (DARI) in Maragheh. The treatments included three sowing dates (early, customary and late), three levels of single irrigation (Rainfed, 50mm and 100mm (only at planting time) along with five wheat varieties (V1(72YRRGP), V2(Fenkang15/Sefid), V3(Turkey…), V4(Azar2), V5(double cross shahi)). Grain and straw yields as well as degree day index were studied for different SD and SI treatments. The highest grain yield at SI levels and rainfed conditions were for V3 and Azar2 wheat varieties whilst grain yield of V1, V2 and V5 wheat varieties were less than those of the other varieties. The results indicated that 100mm single irrigation at early SD is indispensable while 50mm single irrigation sufficient at late SD. In general, based on interpolation method, optimum single irrigation program for rainfed wheat were recommended based upon 100 – 75 – 50mm water use at early, customary and late SD respectively. Thus, when limited single irrigation is combined with appropriate management, wheat production can be substantially and consistently enhanced in these areas.

High spectral resolution in hyperspectral images and their ability of imaging in narrow bands, make them highly capable in investigating and monitoring vegetation and crops. Due to the high number of bands in the hyperspectral images, selection of optimum bands for monitoring a specific parameter is indispensable. For this, absorption bands of different materials and the relevant defined indices can be deployed. In this research, regarding the absorption bands of the substances under consideration, 17 optimum bands were selected. Then, using these bands, different vegetation indices were defined and implemented on the images. The results of each index on the image were investigated and the outcoming results divided into different regions. To get access to applicable results, Decision Tree classification method was applied in the second stage. The resultant output of this method of classification revealed that this method can be used in the relative determination of the plant stress and as a whole, the health and vigour of the vegetation under study in the region, resulting in their classification in this respect. Also this research revealed that, by using these images, one can investigate and monitor the green vegetation, the parameters affecting their vigour as well as discover the stresses which cannot often and otherwise through naked be detected eyes.

This study was conducted to characterize the reactivity of carbonates in the surface horizons of 20 soils (Entisols and Aridisols) from central region of Iran. The samples were analyzed for Calcium Carbonate Equivalent (CCE), Active Calcium Carbonate Equivalent (ACCE), Non-active Calcium Carbonate Equivalent (N.ACCE), carbonate mineralogy and surface area of carbonates (SSA) through N2 adsorption. The CCEs ranged from 38 to 228g kg-1 of soil, with a mean of 105.1g kg-1 of soil. ACCEs1 (while not being sieved through 1mm sieve) ranged from 9.9 to 90.5 with a mean of 32.7gkg-1 of soil and ACCEs 2 (after being sieved through 1mm sieve) ranged from 13.4 to 99.8 with a mean of 37gkg-1 of soil. About 32% of the calcium carbonate (without being sieved through 1mm sieve) and about 34% of CaCO3 in the soils reacted with oxalate. The average surface area of soils as estimated from the N2 adsorption (BET) was 19.75 m2 g-1 of soil and the average surface area of carbonates was 103.2 m2 g-1 of calcium carbonates. The surface area of carbonates was significantly correlated with clay content (r = 0.46*, n=20) and with CCE (r=-0.52*, n=20), indicating that with increase in CCE content, the surface area decreases. X-ray diffraction (XRD) analysis showed that Mg- Calcite [Mgx Ca1-x (CO3)] is the most commonly cfound carbonate in the studied soils. Dolomite was identified in only 7 soils.

Realizing the difficulties involved in direct measurement of soil properties, in recent years, alternative methods have been employed. In the present research, soil texture, organic carbon, saturation percentage and lime as readily measurable parameters, wilting point, field capacity, cation exchange capacity as well as bulk density, as predicted variables were evaluated. The data set was then divided into two subsets for calibration (80%) and testing (20%) of the models. For a prediction of the mentioned parameters, neuro-fuzzy, artificial neural network and multivariate regression were applied. In order to assess the models, some such evaluation parameters as root mean square, average error, average standard error and coefficient of determination were taken into account. Results revealed that the neuro-fuzzy model gives a more appropriate estimation than the other techniques for all the characteristics where this model increased accuracy of predictions for about 34, 10, 78 and 5% for FC, PWP, CEC and BD respectability. Next after neuro-fuzzy model, artificial neural network was of a higher accuracy than multivariate regression.

The effect of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria, with the ability to produce ACC deaminase enzyme, on water relationships and agronomic indices of sunflower (Helianthus annuus L.) cultivars was investigated. The soil used was of an EC equal to 7.6 dS m-1. A greenhouse factorial experiment on the basis of a completely randomized block design with three levels of arbuscular mycorrhizal inoculants ¬(non inoculation¬, inoculation with¬ Glomus etunicatum and G. intradices), four levels of Pseudomonas fluorescens¬ inoculants (non inoculation, inoculation with P. fluorescens strains 4¬,9,12) on two cultivars of sunflower (Euroflor¬ and ¬Master) with four replications per treatment was conducted. Results indicated that treatments significantly (P<0.05) increased Relative Water Content (RWC) of the two cultivars. Single inoculation of P. fluorescens strain12 and Glomus etunicatum as well as co-inoculation of fungi with each one of the bacteria enhanced wet and dry weight of tray in Euroflor cultivar, as compared to control.

Shortage of irrigation water, being a crucial problem in arid and semiarid regions, makes it necessary to use treated wastewater in agriculture. A field experiment was conducted to investigate the effect of treated municipal wastewater (TMW) on the yield and fiber quality of cotton (Gossypium hirsutum L.) (Mehr variety). Treated municipal wastewater was supplied from Shahrake Ghods sewage treatment plant in Tehran. The experimental treatments were: irrigation of the crop through surface irrigation by different mixtures vs. intervals of freshwater and TMW. Two additional treatments, namely: the cotton crop irrigated with freshwater vs. TMW which were considered as control. The experimental design was a randomized complete block one, consisting of eight treatments and three replications. The results showed that cotton yield, number of bolls per m2, leaf area index (LAI) and plant height were significantly greater when the crop irrigated with TMW rather than with freshwater. The yields in TMW vs. freshwater treatments were about 2200 and 780 kg of lint ha-1, respectively. Also, there was no significant detrimental effect observed on the characteristics of cotton fiber quality when the crop irrigated with TMW.

Development of argillic horizon in loess derived soils under Xeric and Udic soil moisture regimes was studied in Golestan Province. Soils were classified as Hapludalfs and Haploxeralfs. High leaching, stability of the surface, forest vegetation,structure and well drainage conditions provide appropriate conditions for clay migration through the profile and formation of argillic horizons. In the studied soils, the main observed pedofeatures were clay coatings and decalcified zones. Clay coatings were observed mainly in soils with crystallitic-speckled and speckled b-fabric, with smectite and vermiculite as dominant clay minerals. Laminated and thick clay coatings were seen in vermiculitic soils along with calcite infillings, hypocoatings and dominantly decalcified zones. Type of clay minerals, shrink/swell properties, and level of precipitation are factors affecting the abundance of clay coatings. In the well-developed horizons, the occurrence of vermiculite clay mineral has reduced the shrink/swell potential and increased the amount of clay coatings. A high carbonate content (CaCO3) in the lower horizons was the result of re-calcification processes. This hypothesis is supported by the more extensive amounts of CaCO3 in lower horizons than in the upper horizons as well as calcite coatings along the channels and voids. Parameter analysis through MISECA development index showed that clay coatings and calcite depletion pedofeatures were the major factors of MISECA index for the development of argillic horizons. Moreover, results showed that, in addition to the climate factor, extent and kind of clay minerals affected the development of the argillic horizons.

The purposes of this research were to the evaluation of resistance to nickel and cadmium in 52 indigenous and non-indigenous strains of contaminated soils and a study of growth promoting characteristics of some resistant isolates. Resistance test at three levels of cadmium (0, 100, 200 mg l-1) and five levels of nickel (0, 250, 500, 750, 1000 mg l-1) in the framework of a completely randomized design of three replications was conducted. Indole acetic acid producing ability, production of ACC- deaminase enzyme and siderophore, solubilization of organic and inorganic non-soluble phosphate were determined as plant growth promoting characteristics. The results showed, from 52 strains, 10 strains (19.2%) were resistant to high levels of nickel and cadmium. From amongst ten strains, two isolates 105 and 109 were not only the most resistant to nickel and cadmium but also had some plant growth promoting characteristics.

Finding the most appropriate governing equation under different environmental conditions is the most important step for both designing sorption systems and pollutant transport modeling. In this study, the second order model based on the sorbent concentration is theoretically and experimentally investigated. A circular flume was used for the sorption of cadmium by zeolite to simulate the natural conditions. The results indicate that the various equations proposed by different researchers for the sorption are the same and the differences are only due to the linearization and parameter definition methods. The results also state that linear R2 could not be used unaccompanied to determine the best linearization method and it should be used with the sum of square error (SSE). Comparison between seven linearization methods with current data showed that the methods of Sobkowsk and Czerwinski, Ritchie and Blanchard are the best linearization methods for linearization of the second order kinetic equations. Finally it was found that the sorption capacity should be experimentally measured.

In order to study the effects of pH and the ratio of nitrate to ammonium in nutrient solution, on the growth characteristics and on the yield of spinach (Spinacia oleracea L.), a factorial experiment was conducted consisting of two factors including: nutrient solution pH in three levels (4.5, 6.5 and 8) and nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75 and 0:100). The experiment was carried out in a completely randomized design with four replications in perlite culture in greenhouse conditions. The results indicated that by decreasing the ratio of nitrate to ammonium in nutrient solution, leaf chlorophyll index was increased. By decreasing the nitrate to ammonium ratio from 100:0 to 75:25, net photosynthetic rate, leaf number, leaf area, fresh and dry weights of shoots were increased. With further decrease in nitrate to ammonium ratio, the above factors were decreased. By increasing the nutrient solution pH from 4.5 to 8, leaf chlorophyll index, net photosynthetic rate, leaf area and fresh as well as dry weights of shoots were decreased. The interactive effects of pH and the ratio of nitrate to ammonium in the nutrient solution on net photosynthetic rate, leaf number, leaf area and fresh and dry weight of shoots were significant, so that a pH of 4.5 with nitrate to ammonium ratios of 100:0 and 75:25, pH 6.5 with nitrate to ammonium ratio of 75:25, and pH 8 with nitrate to ammonium ratios of 75:25 and 50:50 yielded a the maximum dry weight of shoots.

To study the effect of nitrogen form and pH of nutrient solution on the uptake and concentration of Fe, Zn, Cu and Mn in roots and shoots of spinach plant, a factorial experiment was conducted with two factors including nutrient solution pH in three levels (4.5, 6.5 and 8.0) and nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75 and 0:100). The experiment was carried out in a completely randomized design with four replications in perlite culture and greenhouse conditions. The results showed that the effect of nutrient solution pH on the root concentration of Fe and Cu, shoot concentration of Fe, Cu and Mn, uptake of Fe, Cu, and Mn was significant, but the effect on the root and shoot concentration of Zn and Zn uptake was not. By increasing the nutrient solution pH from 4.5 to 8.0, uptake of Fe, Cu and Mn, as well as in shoot concentration of Fe, Cu and Mn were significantly diminished, but root concentration of Fe and Cu was significantly increased. While Zn uptake, root concentration of Zn and Mn, and shoot concentrations of Zn did not change significantly. The effect of nitrate to ammonium ratio of nutrient solution on the root and shoot concentration of Fe, Mn and Zn, shoot concentrations of Cu, as well as the uptake of Fe, Mn, Zn, and Cu by plant was significant. By increasing the ammonium concentration of nutrient solution, the root and shoot concentration of Fe, Mn, Zn, and Cu, as well as their uptake (by spinach plant) were significantly increased, but by further increasing the ammonium concentration, their uptake, the root concentration of Mn and Cu, and the shoot concentration of Fe and Mn further decreased. Also, the effect of nitrate to ammonium ratio of nutrient solution on the root and shoot concentration of Fe, Mn, Zn, and Cu, along with their uptake by the plant was dependent on the nutrient solution pH and vice versa. In general, the maximum amount of Fe and Zn uptake by spinach plant was in nitrate to ammonium ratio of 75:25 and pH of 6.5, but a maximum level of Mn and Cu uptake was observed in nitrate to ammonium ratio of 75:25 and pH of 4.5. The plant accumulated Mn and Zn in its shoots but Cu and Fe in its roots.