مجله تحقیقات آب و خاک ایران
سال چهل و هشتم شماره 1 (پیاپی 28، فروردین و اردیبهشت 1396)

The nitrogen demand during growing period is variable for plant, but most farmers use large amount of nitrogen without the knowledge of the proper time in order to achieve maximum product. This pattern of fertilizer consumption causes environmental pollution. The optimum demand of nitrogen during growing period could be determined by the critical nitrogen equation. The main objective of this study was to determine the coefficients of the critical nitrogen equation for maize in Pakdasht. Comparing these coefficients with suggested coefficients in France and China was the second objective of this research. The maize (single cross 704) for a season was planted on the farm of Aburaihan campus. The aboveground biomass (W) and its critical nitrogen concentration (Nc) were measured in six different times, from 26 days after planting to the harvesting time. The coefficients of critical nitrogen equation were determined using theory of critical nitrogen dilution curve. Finally, the equation of Nc = 2.9 W -0.27 as nitrogen critical dilution curve was proposed for maize in the Pakdasht. The results showed that the nitrogen status was mispredicted in 21% and 14% of measured data point, by France and China equations respectively while this erorr was only 9% by using the equation provided in this study. The main reasons for these errors are differences in climate and prevalent varieties of maize in different areas.

Crop phonological stages are commonly predicted by using accumulated growth degree days(AGDD).In this study a combined model of AGDD and remotely sensed NDVI has been developed for prediction of maize (cv. K407) phenology in Karaj using a nine year (2002 to 2010) dataset. For smoothing the existing noises of image processing, a combination of double logistic and weighing average (DL-WLS) approaches was employed. The results of combined phenology model were compared by two frequently used methods based on AGDD and date of sowing. The findings showed that in general, the developed model predicted the first 7 phenological stages of emergence to milky, more accurately comparing to other approaches (with average 2 and 2.5 days difference with observed dates, respectively) but was inaccurate for maturity stage. Our study highlights the need for further improvements in observations in the region.

In this study the effects of soil matric suction (2−33 KPa) and salinity (EC: 0.7−8 dSm-1 for bean and 2−20 dSm-1 for wheat) on the wheat and bean nutrient concentrations in two sandy loam and clay loam soils at green house condition was considerd. The potassium concentration increased and sodium decreased with matric suction in both plants. The nitrogen and calcium concentrations of bean and wheat increased with matric suctions and reached their extreme values at suctions 6-10 KPa. Concentration of nitrogen reduced and concentration of calcium remained nearly constant at higher suctions. The maximum concentration of iron and zinc were at suction 2KPa in both plants. As matric suction increased from 2 to 6 KPa, iron and zinc decreased strongly and remained nearly constant at higher suctions in both soils. Salinity increased concentrations of iron and calcium and reduced concentration of potassium in both plants. While it did not affect concentrations of nitrogen, sodium and zinc. The low soil matric suctions amplified the salinity stress due to aeration deficit. Also comparing two plants showed that because of high sensitivity of bean to stresses, changes of its nutrient concentrations under different levels of salinity and matric suction were greater than wheat.

The parameters of infiltration equations have a key role to evaluate and design irrigation systems. Therefore, in order to enhance irrigation efficiency, it is necessary that these parameters to be estimated precisely. In this study, four inverse estimation methods to predict the coefficients of infiltration equation including two-point method, multilevel optimization, SIPAR-ID, and IPARM in the vegetated furrows were assessed and compared together using the field data. The field study in order to collect required data was conducted in Karaj in 2014. Seven irrigation events were performed during the growing season of the maize with two inflow discharges of 0.29 and 0.44 l/s. Based on the estimated coefficients of infiltration equation, the IPARM model with average relative errors of 1.24 and 1.52 %; as well as the multilevel optimization method with average relative errors of 1.44 and 1.58 % had the best performance for inflow discharges of 0.29 and 0.44 l/s in estimating infiltrated water volume, respectively. The SIPAR-ID model had a poor and fluctuating performance in estimating the coefficients of infiltration equation in the vegetated furrows. Moreover, the two-point method presented an acceptable performance with average relative error less than 10 percent in estimating infiltrated water volume.

Recently, FAO has proposed the version 4 of AquaCrop model that can simulate the effect of irrigation with saline water on yields and soil salinity. In this study, the AquaCrop model was evaluated under different agriculture managements and irrigation with saline water for Maize (SC.704). Field experiments of this study were done in the agriculture farm of Shahid Chamran University. Different crop managements included without crop residues, use of crop residues on soil surface as mulch and mix of crop residues with surface soil layer to 30 cm depth and water irrigation salinity at three level included water salinity of Karoun river ( On average 2ds/m), 4.5 and 7 ds/m. After model calibration to offset some input parameters, model validation was performed. The amount of determination coefficient (R2), relative error (RE), coefficient of residual mass (CRM) and Normalize root mean square error (NRMSE) in validation for soil salinity were respectively 0.83, 10.6%, 0.04 and 11.64, for yield were respectively 0.93, 5.2%, 0.01 and 5.58, for biomass were respectively 0.99, 4.2%, -0.02 and 4.48 and for canopy cover were respectively 0.97, 16%, 0.08 and 14.71. The average error in use and not use of Wheat residues for soil salinity was respectively 9.6% and 12.7%, for yield was respectively 6% and 3.5%, for biomass was respectively 4.8% and 3.1% and for canopy cover was respectively 14.6% and 18.8%. The results showed that soil salinity, yield, biomass and canopy cover were simulated well. However, the model accuracy was lower to estimate of soil salinity and canopy cover and it was decreased with salinity increase. Also, the model accuracy was increased in soil salinity and canopy cover estimation and was decreased in yield and biomass estimation under agriculture managements application condition.

In this research, impact of different levels of magnetized wastewater were investigated on yield and water use efficiency in maize cv. Maxima and some of soil physical properties. Research was done as factorial experiment with two factors based on complete randomized blocks with 3 replications from June to October 2014 in Research Farm of Zanjan University. Required wastewater was provided from refinery of Zanjan and was distributed in plots in 5 levels included 0% (well water as control), 25, 50, 75 and 100%. Magnetic water was included crossing and no crossing magnetic field. Based on results, leaf area and relative water content of leaf were not significant affect by different levels of wastewater. Maximum value of maize wet mass and water use efficiency for wet mass were in 100% wastewater treatment which were significantly difference with control treatment as 23.9 tone/ha and 7.6 kg/m3 respectively. Difference between maize wet mass and water use efficiency of wet mass for magnetized and no magnetized water were 14.6 tone/ha and 4.7 kg/m3 (respectively) which were statistically significant.
In this study, effect of different levels of wastewater were not significant on soil physical properties in 0-15 and 15-30 cm depths. The effect of magnetic water on soil physical properties was significant in 0-15 cm of soil depth but there was not significant influence in 15-30 cm depth. Results showed, in 0-15 cm of soil depth, magnetic water increased soil bulk density, volume moisture and soil saturate degree and decreased soil porosity compared to no magnetic water as 19%, 3%, 10% and 8% (respectively).

Initiation time and production rate are the major runoff characteristics which can be affected by the changes of soil physical properties during rainfall. Temporal variation of these characteristics could be controlled by soil texture and slope gradient. This study was carried out to investigate temporal variation of runoff in both different soil textures those of clay loam, loam, and sandy loam and various slopes (5, 10, 15, 25(and 30) under a 40 mm h-1simulated rainfall in the lab. Soil texture and slope steepness were the important factors influencing runoff initiation time (P

This paper aims to increase the accuracy of runoff predictions using WAPABA model and with comparing its efficiency with SALAS model outputs, involving hydrometric runoff data of North Markazi Province-Iran, for year 2010-2011. The above mentioned models were applied and calibrated using the mentioned historical data. Then the performance of each model were evaluated using different criteria including; CE, RMSE, R2 and MAE. Also, comparison of the models predictions with the measured data were made. Results show that the predicted runoff data using SALAS model are values more than the measured data, which can be due to the weighting values of this model. In other words in SALAS model the weights which relate to precipitation is more than other parameters. While WAPABA runoff model with the same weights, which are considered for all parameters, have a better and accurate predictions. However, in this study for the Ghet-e-Char station of the case study WAPABA model had not suitable predictions.

Potassium (K) is one of the essential nutrients for plant growth and it is found in the structure of many silicate minerals of soils. Soil microorganisms such as bacteria, fungi, algae and lichens have high efficiency in silicates decomposing and releasing elements such as potassium. The purpose of this study was to model and evaluate the effects of pH, incubation time and different amounts of feldspar on K release by Bacillus sp. For this reason different ranges of these three variables, including pH (5-9), incubation time (1-17 days) and feldspar (1-7 g.l-1) was considered and a central composite design with 20 experiments was used to evaluate the effects of the coded independent variables on K release from the feldspar. Results indicated that the central composite design has high efficiency (R2= 0.982, RMSE= 1.96mgl-1) in predicting soluble K concentration. Sensitivity analysis of the central composite design revealed that the pH and treated feldspar concentration are the most important factors in K release and the effect of these factors on K release are 37.48 and 31.80 percent, respectively. The highest concentration of the K was observed at high concentrations of feldspar and lowest levels of pH. Incubation time also had a significant effect on potassium release. In the early stages of the incubation time, the trend of potassium release was increased, in middle stages, K amount decreased but it was accelerated at the long times of incubation. Generally, increasing of the feldspar concentration and incubation time along with low initial pH lead to the high amounts of K release from feldspar.

Soil erosion is one of the basic environmental problems in the developing country such as Iran and can be destructive effects on ecosystems. The aim of this study was to investigate the gravel fragment effects on runoff and soil loss in the watershed of Almas Bridge, Ardabil. For this research after the surveys in the area, three class slopes (6, 15 and 22%) were identified in the region. In each slope class, treatments consisted of gravel coverage zero, 10, 20 and 30% were applied. A factorial experiment was carried out in a randomized complete block design. Results showed that the maximum runoff volume, soil loss, sediment concentration and runoff coefficient were in the control treatment (without the gravel fragment coverage) in the slope of 22% and the minimum of them were in treatment with 30% of gravel fragment coverage in the slope of 6 percent. The results depicted that the runoff volume and soil loss were decreased 96% and 519%, respectively, using 30% gravel fragment coverage in compared with the control treatment. On the other hand, the finding of this research illustrated that the generated volume of runoff on the slope of 22% is 37 and 107 percent more than the slope of 15% and 6%, respectively. In additional, 20 and 30% of gravel fragment coverage in the slope of less than 15% were shown the most effect on the soil loss, sediment concentration and runoff volume.

Quantitative, continuous and three-dimensional soil data at appropriate scales are prerequisites for modeling of natural resources and environment. Despite the importance of soil texture, its legacy soil maps are often provided for the surface layers in which vertical and lateral variations of soil properties are not considered. The combination of digital soil mapping (DSM) and soil depth functions is an alternative tool to cope with these problems, especially in countries with limited data such as Iran. Therefore, equal-area spline depth function and DSM techniques were employed to assess the vertical and lateral distribution of soil texture in Silakhor Plain, located in Lorestan province, western Iran. By fitting the depth function to the measured clay, silt and sand percent in 103 sites to a depth of one meter, their estimated percents were obtained at five standard soil depths of Global Soil Map project (0-5, 5-15, 15-30, 30-60 and 60-100 cm). Also artificial neural network model was employed to predict lateral distribution of soil texture fractions using the auxiliary variable derived from satellite image and digital elevation model (DEM) in the standard depths. The results of the sensitivity analysis showed although the relative importance of auxiliary variables in predicting soil texture was different according to the depth and texture fractions, the performance of artificial neural network in upper layers was more than lower layers. R2 values for clay, silt and sand and from the top to the bottom were 0.73 to 0.49, 0.43 to 0.76 and 0.26 to 0.68, respectively. Results also showed, for estimating soil texture, auxiliary variables derived from satellite image were more important in surface layers and of DEM were more important in subsurface layers.

Soil carbon changes is one of the most important indicators impacts of climate change impacts on soil genesis. Study of soil carbon, including organic and inorganic carbon (carbonates) and its impact on other soil characteristics in different climates, is essential for the proper management of soil carbon on a global scale. It is too important the balance between different parts of carbon sources in the environment. In current study, organic and inorganic carbon complex with primary particles were studied in 9 profiles a climosequence including three climates arid, semi-arid and semi-humid with typic aridic, dry xeric and typic xeric moisture regimes and mesic and thermic temperature regimes. Results showed that the amount of organic carbon in all three components decreases with increasing depth and also clay component has more organic carbon content in all depths compared with other components of soil. Contrast to organic carbon, inorganic carbon content is lower in surface horizon compared with the subsurface in all three components of particle size and increases with increasing depth. The avearage of organic carbon components of particle size in three studied regions showed that the following trend clay (1.1%) > silt (0.68%) > sand (0.23%), while inorganic carbon in the soil with trend silt (14.41%) > sand (12.11%) > clay (8.14%).

Vast parts of the world soils including Iran have calcareous soils in which due to the high pH and fixation of many micronutrients including zinc (Zn), the deficiency of these nutrients are seen. Total Zn content in soils does not give any information about it’s availability to plants. Therefore, available zinc in 28 calcareous soils with a wide range of physical and chemical properties was evaluated with DTPA-CaCl2, EDTA-NH4OAc, DTPA-NaOAc, DTPA-NH4HCO3, EDTA and Mehlich3 on pistachio seedling as a test plant. Experiment was done as a completely randomized design with three replications and 28 soil types under greenhouse conditions. The results showed that the ability extractants to extract zinc are as follows: Mehlich3 > DTPA-NaOAc > EDTA> EDTA-NH4OAc > DTPA-CaCl2 = DTPA-NH4HCO3. Use of multiple regression equations showed that amount extractability of Zn by some extractants from the soil by some of the physical and chemical properties soil, such as clay, CEC and CCE was dependent. There was a significant correlation between concentration and uptake zinc of the leaves and stem and extractability of Zn by the extractants . So that the amount of zinc extracted by DTPA-NH4HCO3 highest correlation (R= 0.634**) with the concentration zinc of pistachio seedlings leaf, so extractant DTPA-NH4HCO3 can be used to evaluate available zinc the pistachio in calcareous soils.

Effects of K-depletion on K-Ca exchange equilibiria were studied in a clay separated from a soil with dominant illite (mica) mineralogy. Treatment of clay with NaTPhB㖠 for periods of 6, 25 and 150 hours resulted in release of 22.1, 30.8 and 40.7% of total K, respectively. K release was much faster at first and then gradually decreased with the time. Cation exchange capacity (CEC) of the clay increased with K-depletion, indicating that at least some of the K was released from the interlayers of the clay. Mineral weathering contributed significantly to the total extracted Ca. Thus, exchangeable Ca values overestimated by 31.2 to 76.7% when weathering was neglected. Anion adsorption was found to be more than negative adsorption. Comparison of exchange isotherms of K-Ca with non-preference isotherm indicated that K was preferred over calcium up to ẼK≤0.8 in non-depleted clay and up to ẼK≤0.76 in depleted clays. Slight preference of Ca over K was observed on ẼK>0.8. Comparison of K-depleted clay’s exchange isotherms demonstrated that selectivities of exchangers were not affected by K-depletion. A study of XRD patterns of the K-depleted clays after treatment of the clay with a solution having 0.05 equivalent fraction of potassium showed that during the K-Ca exchange, layers were collapsed, but CEC values of these clays indicated that the layer collapse of the clays were not complete. Apparent K preference was increased with ionic strength, and with dilution of equilibrium solution, more Ca was absorbed. The difference between the two exchange isotherms at the two different ionic strengths was a result of valence-dilution effect.

The effect of surface rock fragments on soil erosion processes has been an important challenge in erosion studies during the last two decades. Rock fragment characteristics including size, position and coverage may affect soil erosion and cause a complication in predicting their effects on soil loss. The aim of this study was to model the effects of rock fragment coverage, size and the flow rate on soil loss and surface flow velocity employing response surface method and central composite design. Two sets of run-on simulation experiments were carried out in a laboratory flume (6×0.5m). The range of the independent variables were 0-45 percent for rock fragment coverage, 3-9cm for rock fragments diameter (size) and 1.67-5 cm3cm-1s-1 for flow rate. The second set of experiments used to develop the predictive model based on the central composite design and the results of the first set of experiments were applied to validate the predictive model. Results indicated that the central composite design models have high performance in predicting flow velocity (R2=0.993) and soil loss (R2=0.994). Models validation with the first data set also indicated a good agreement between the predictive values of flow velocity (R2=0.887) and soil loss (R2=0.851) with the experimental values of these two variables. Rock fragments coverage, flow rate and the size of the rock fragments have the highest influence on soil loss and flow velocity, respectively. There was a significant interaction between the flow rate and rock fragment coverage, which should be considered in modeling of their effects. A linear relationship was also observed between the flow velocity and soil loss.

Infiltration plays an important role in surface and subsurface hydrology and is a key factor in the whole rain fall-run off equations. This research was carried out Behshahr- Galugah coastal plain. With attention to most agricultural crops of region are grown in this plain and the importance of water permeability in soils, permeability studies in this area seem necessary. 10 km × 8 km grid was used to sample with the grid cell size is 1000 m2. Measuring water infiltration was performed using a single cylindrical ring considering infiltration height of 1 cm and variable time. After the measurements, the infiltration rate of the soil was estimated using both Horton and Kostiakov equations and was compared to the observed values. For selection of an appropriate model evaluation criteria including RMSE, RE and NSS for each equation were used. The values of these criteria for Horton equation were 5.55, 24.61 and 0.98 and for Kostiakov equation were equal to 8.5, 64.14 and 096, respectively. The results showed that the Horton equation has more accuracy in estimation of infiltration to Kostiakov equation compared with observed values in this region. Also investigation of spatial variability of permeability rate with GS version 5 software was showed that semivariogram of variable was isotropic and there was strong spatial dependence between water permeability.

Scouring and internal erosion always have created problems for earth dams. So that internal erosion or piping is known as the second causing the earth dam failure. In this study, nanoclay is used as a new additive without environmental problems, to reduce the piping erosion of silty sand soil. To investigate erodibility samples containing nanoclay with 0, 1, 2, 3, 4, 5and 6 weight percent of dry soil were used and run the Hole Erosion Test (HET). Then the impact of compaction, moisture content and hydraulic gradient on erosion of samples with 1% nanoclay were investigated. The results show that by adding 1% nanoclay erosion rate index increased more than two times, that means the erodibility reduces. Erodibility of sample containing 1% nanoclay at the most hydraulic gradient was changed from very fast group to moderately slow group.

In this research variation of moisture and volume of an unsaturated silty soil were investigated under different suctions through experimental tests in triaxial apparatus special for unsaturated soils. The tests were carried on specimens of silty soil that made by slurry method in modified triaxial cell (triaxial cell with doubled rings) under 5 suctions from 0 to 300 kPa. Applying the target suction have been done by axis translation technic and loading the specimen under constant suction was carried by using increment loading. The results show that preconsolidation pressure will increase by increasing suction. Furthermore according to the obtained results, creation of yielding curve (LC) in space of stress- suction is possible. Also investigation of variation in slope and intercept of normal compression line showed that variation of volume and moisture of soil is function of suction changes.

Vegetative buffer strips include a special plant being passed by the flow before entering the waterbodies; so, it causes runoff volume reduction, accumulated pesticides and other pollutants of the flow by infiltration, uptake and sediment deposition. The present study has been conducted with aim to evaluate and comparing the impact of vetiver grass, native turf grass of Sari (Mazandaran) and a combination of the two mentioned species on the efficiency of vegetative buffer strips in reducing the surface water pollutants including sediment, nitrate and phosphate. The experiments were carried out using 1×10 m experimental plots and producing artificial runoff with a flowrate by 1.65 l/s during a year. the vegetative buffer strips used in this study reduced the runoff volume by 35-90%, sediment concentration by 42-94%, nitrate concentration by 35-88% and phosphate concentration by 28-95% so that, all maximum efficiencies were related to the treatment of vetiver grass-turf grass. According to the results, the vetiver grass has a high efficiency in reducing and controlling the runoff pollutants; but, due to the probability of the creation of concentrated flow among the bushes of vetiver grass, using a resistant plant adapted to the region climate with a density and uniformity similar to the turf grass is recommended to make the flow uniform and sheet and consequently increasing the efficiency of vegetative buffer strips to reduce runoff volume and pollutants before entering the runoff to the surface waters. Also, periodic mowing of the plants is given as an effective strategy to deal with the role of vegetative buffer strips as the source of nutrients and sediment.

Soil tillage is one of the most important practices in agricultural production. Farming and tillage accompanied with slope direction result to not only in increasing soil loss but also in decreasing soil organic carbon content with a consequent reduction in the aggregate stability on steep lands. The aim of this study was to investigate the effect of tillage direction, slope position and slope direction on soil aggregate stability and some physical and chemical properties of soil. For this purpose, soil samples were collected from an area with contour tillage located in the Soil and Water Conservation Research Station of Kuhin and its adjacent area outside the station with up-down tillage. The area was as a shallow valley with the northern and southern faces. Soil samples for both tillage types were taken from upper, middle and bottom of the slope in two depths with three replications (72 samples). Data were analysed based on the nested design. The results showed that most of the soil measured properties were highly affected by soil tillage in which, up-down tillage caused reduction in the soil quality. Furthermore, the results demonstrated that the slope direction and position can only affect soil aggregate stability index, while all four indices of aggregate stability were significantly affected by tillage type. Organic matter content is a major reason for increasing soil aggregate stability in the contour tillage. The position and direction of slope in addition to field management have very complicated effects on soil properties at various depths. Finally it concluded that soil aggregate stability is significantly influenced by all types of changes including the position and direction of slope and soil depth.