فصلنامه حفاظت منابع آب و خاک
سال هفتم شماره 1 (پیاپی 25، پاییز 1396)

Runoff is the major soil erosive factor which can be controlled to different factors such as hillslope length. Knowledge of the role of hillslope length in runoff can help in designing soil conservation practices particularly in rainfed lands. This study was carried out to investigate the effect of slope length on runoff in rainfed lands of semi-arid regions, north west of Iran. Twenty two plots with different lengths ranging from 1 to 22.1 m and with the same width were installed on a 10% slope according to the Universal Soil Loss Equation model. Runoff characteristics (total runoff volume, runoff per area and runoff coefficient) were determined for a fourteen-month period from March 2015 to Jun 2016. The results indicated that significant difference was found among the plots in total runoff volume (P

Gypsum soil is one of the problematic soils because of considerable solubility for gypsum particles in contact with water. In this research, the effects of three factors including; gypsum percent, hydraulic gradient, and soil texture were studied on solubility of gypsum soils. To do this, samples of gypsum soils were provided artificially by adding various rates of natural gypsum rock including 0, 5, 10, 20 and 30 percent by weight of 3 kinds of soil textures including clay, silty clay and sand. Totally, 15 types of gypsum soils were prepared. Then each of gypsum soils were leached under five hydraulic gradients levels 0.5, 1, 2, 5 and 10. The results of the test indicated that the rate of gypsum in the soil has direct effect on the rate of soluble in a way that by increasing percent of gypsum the rate of solubility was increased. in addition, by increasing hydraulic gradient, the speed of water outcome and its amount from soil environment in a specified time was increased and also more rate of gypsum was derived. The statistical results show the highest impact of gypsum percentage and lowest impact of hydraulic gradient soil on solubility of particles in different types of soils and it has no significant effect on the overall equation of the soil texture.

The water infiltration into the soil is an effective factor on runoff generation and watershed situation. Although many approaches have been therefore developed to improve infiltration process, but, less attention has been paid to use nano-paticels individually and in combination with organic amendment with the aim of improvement of water infiltration into the soil. The present research has been hence planned to assess the effect of organic vermicompost (V) amendment in 100 g m-2 and silica nanoparticles in 3 levels of 3, 7 and 10 g m-2 individually and in compound on infiltration of a sensitive soil to erosion from Marzanabad-Kandelus at small plots scale under experimental situation. The water infiltration measured under rainfall simulation with intensity of 50 mm h-1 and 50 min duration and different treatments and the statistical analysis was accordingly conducted. The results showed that all treatments except silica nanoparticles level three (NS3), increased the infiltration and decreased runoff volume compared to the control treatment. The water infiltration into soil in the cases of (V), silica nanoparticles (level one( (NS1), silica nanoparticles (level two) (NS2), vermicompost and silica nanoparticles (level one ) (VNS1), vermicompost and silica nanoparticles (level two) (VNS2), vermicompost and silica nanoparticles (level three) (VNS3) increased by 24.79, 30.63 , 10.18, 14.05, 15.09 and 23.30 %, respectively and the (NS3) decreased by 0.24 %. The differences between performance of individually and combined application of vermicompost and silica nanoparticles confirmed the necessity of the correct usage of amendment in soil and water management.

Nowadays, Soil erosion is one of the largest problems of the world, particularly in Iran. side effects and dangers of this phenomenon within the watershed field is the main problem that affected the overall ecological balance of the basin. The main objective of this study was to determine the optimal level land use for reducing erosion and enhance stakeholders income at Saghezchi watershed is located in the Ardebil. For this aim, linear programming model for three different options include current situation land uses, standard land use and standard conditions with biological measures land use in accordance with scientific principles and criteria were used. The results showed that the current land use level to reduce erosion and increase the income of residents is not suitable and in optimal conditions must be changed. in optimal conditions the garden lands level from 132.29 hectare to 1902.83 hectare (1438.4 % increased), rangeland level without change, irrigated land surface from 319.94 hectare to 57.6 (81.99% decrease) and rainfed cultivation is also from 1549 hectare to 40.8 hectare (97.36% decrease) was changed. In addition, the results showed that land use optimization in the current situation, The ratio of soil erosion and total profitability, 0.07% decrease and 7.7% increase respectively, at the standard conditions land use 3.72% decrease, 7.7% increase respectively and at the standard conditions with biological measures land use, The ratio of ​​soil erosion and total profitability, 5.48% decrease and 30.65% is increased respectively.

Biochar is a charcoal made from biomass and animal manure, which is produced by thermal decomposition under a limited or zero supply of oxygen. Therefore, the current research was conducted to evaluate the effect of different biochar levels on some soil physical and chemical properties in four soil types under greenhouse conditions. The experiment was performed in completely randomized design with four levels of biochar produced from wheat straw in 500oC (0 (as control), 25, 50 and 75 ton ha-1) and four soils having various textures (sandy loam, loam, clay loam and clay) in three replications. Forty days after mixture of soil and biochar and determination of soil moisture content at field capacity, other physical and chemical parameters (soil moisture at permanent wilting point, bulk and particle density, saturated hydraulic conductivity and cation exchange capacity) were measured by taking soil samples from the pots. The results showed that application of biochar enhanced soil physical properties. Increasing biochar levels from 0 to 75 ton ha-1 increased soil available water content, porosity, hydraulic conductivity and cation exchange capacity by 45, 13, 95 and 52 %, respectively. It is concluded that biochar can be used as a soil amendment in coarse textured soil to increase water holding capacity and in fine textured soil to improve the drainage and infiltration.

According to the conditions of any river, different methods are used to protect of erodible rivers bank. One of these methods is the use of banks protection structures such as submerged vanes. The main problem of these structures is to local scour of around the nose structure. One of the effective methods of flow pattern improvement around the structures is creating slot in structure. In this study, has been created rectangular slot (with fixed dimensions) in three different positions in bank attached triangular vane, this means that the slot is parallel to the chord in first vane, parallel to the base in second vane and parallel to the vertical side of triangular vane in third vane. The research aim is to determine the slot optimal location, with defined dimensions. Experiments were conducted in the single-vane posture and under different hydraulic conditions (clear water condition). Results showed that the first vane (slot is parallel to the chord) had the best performance to reduction of volume, Length and width of scouring. Also, the maximum scour depth in this vane was 35% and 13% less than two other vanes that slot is parallel to the base and parallel to the vertical side, respectively.

Nowadays, knowing the amount of soil erosion is an important part of the comprehensive management of watersheds. Due to the lack of sufficient information and data relating to water and sediment discharges in watersheds, soil erosion is estimated using user-friendly models and new technologies. The aim of this study is to predict erosion and sediment yield in the Darkesh watershed, North Khorasan province, using WaTEM/SEDEM model and RS and GIS and image fusion algorithm. At the first, the crop management factor (C) was mapped based on land use map. The Gram-Schmidt algorithm was used to combining multispectral images Landsat 7 and 8 with panchromatic images for the two satellite images with 12-year time distance (2003 and 2015) and a scale of 1:25,000. The maps of other input factors were then prepared using ArcGIS and ENVI software and the model was run and the rates of erosion and sediment yield with the scale of 1:25,000 was predicted with and without image fusion algorithm and were compared with the observed rates in the watershed. Comparing observed sediment data in Darkesh watershed with predicted amounts showed that the final map of erosion classification by applying image fusion algorithm led to better and more accurate identification of erosion sensitive areas. Based on the results of this study, high-performance of WaTEM/SEDEM model to predict of sediment yield was proved and it was found that image fusion algorithm was also led to increase the accuracy of the results.

Water deficit is the main factor that limit growth of plants, so achieving optimal performance under water deficit condition requires the selection of a suitable variety is due to the circumstances of each region. According to this, an experiment was conducted in a split plot arrangement based on randomized complete block design with three replications on soybean in Moghan plain at 2015 and 2016 years. Main-plots were Normal irrigation (IR1), 80 percent of full irrigation (IR2), 70 percent of full irrigation (IR3) and 50 percent of full irrigation (IR4) respectively, Cultivars included Williams (Cul1), M9 (Cul2) and Zan (Cul3) as a sub-plot. The results of comparing the means of data demonstrated that deficit irrigation decreased yield, yield components, percentage of seed oil of all cultivars. Also, the highest its characteristics (yield 4000 kg/hectare, Number of pods per plant 127.33, Number of seeds per plant 240, 1000 seeds weigh 300 gr, biomass 8900 kg/hectare, percentage of seed protein 25.3, WUE (yield) 0.95 and WUE (grain oil) 0.23 kg.m-3) observed in Williams cultivar under normal irrigation and the lowest values for these traits were obtained in Zan cultivar at IR3 and IR4 treatments. Also, the lowest protein content obtained in normal irrigation in the Williams cultivar and the highest that observed in the M9 cultivar at treatment IR4, respectively. Therefore, in order to this results Williams was the best cultivar under normal irrigation and water deficit conditions about yield and M9 was the sensitive variety to the deficit irrigation in Moghan Plain.