نشریه پژوهشهای خاک (علوم خاک و آب)
سال سی و یکم شماره 3 (پاییز 1396)

In order to investigate the effects of mycorrhiza, potassium, and manure application on the yield and quality of pomegranate fruits, in 2014, an experiment were conducted in a randomized complete block design as factorial with 12 treatments and three replicates. Experimental factors included combinations of two levels of mycorrhiza (0 and 500 g.tree-1), three levels of sheep manure (0, 10, and 20 kg per tree) and two levels of potassium (0 and 500 g K2O.tree-1). The measured traits included yield per tree, contents of carbohydrate, brix, and phenolic acids (sinapic acid, gallic acid, catechin, rutin and ascorbic acid) in the pomegranate fruits. The results showed that the main effects of potassium, mycorrhizae and manure were significant (P

This study was conducted to determine the effect of phosphorus fertilization on the grain yield and phosphorus efficiency in different canola cultivars during 2010-2012, at Research Center and Agricultural and Education and Natural Resources Research and Education Center of Ssafiabad, Dezful, Iran. The experiment was arranged as factorial in a randomized complete block design with three replications. The first factor consisted of five phosphorus (Pp) levels (0, 16, 32, 49, and 61 kg.ha-1) and the second factor consisted of three cultivars (Hyola 401, RGS 300, and Sarigol). The result showed that the main effect of phosphorus and cultivars on yields of grain, straw, oil, and phosphorus uptake were significant. The highest of grain and oil yields (2856 and 1128 kg.ha-1, respectively) was were obtained from application of 16 kg P per ha-1 (2856 and 1128 kg -1,respectively). Also, Hyola 401 cultivar had the highest grain and oil yields (2891 and 1137 kg. ha-1, respectively).Phosphorus application led to significant decrease in the phosphorus efficiency indices. Significant differences among the cultivars in terms of performance measurement indicators was were not observed, except indicator of response to fertilizer, so thatwhile the Hyola 401 had the highest response to fertilizer compared to the other cultivars. According to the results of this study, and with regardingconsidering economical analysis, application of 16 kg Pp per ha-1 and Hyola 401 cultivar is recommended.

One of the main reasons of crop yield reduction in Iran is salt stress and providing proper strategies is necessary for mitigating the effect of this stress. So, a factorial experiment was conducted to improve the salt stress damages on two canola varieties in a randomized complete block design with three replications at the Research Greenhouse of Agricultural Faculty of Tarbiat Modares University. Treatments included 3 levels of control, moderate, and severe salt stress (0.4, 5 and 10 dS m-1), calcium silicate at two rates (0 and 8 kg ha-1), two levels of zeolite (control and 8 ton ha-1) and two varieties, namely, Zarfam and Sarigol. Results showed that application of zeolite increased Zarfam yield in soil with a light texture and had no significant effect on Sarigol. Under moderate salinity, zeolite, and calcium silicate treatment, Zarfam produced higher oil percentage (more than 57%) compared to Sarigol at severe stress and without application of zeolite and calcium silicate. Also, Sarigol in the treatment with no salinity stress and zeolite and only application of calcium silicate had the highest oil yield while the lowest oil yield (60 percent lower) was obtained at severe stress, application of zeolite and without application of calcium silicate . In the treatment with moderate salinity and non-application of zeolite and calcium silicate, Zarfam had the highest SPAD, while Sarigol, under moderate stress, application of calcium silicate and without application of zeolite, had the lowest SPAD (more than 32% difference). Generally, salt stress reduced yield and yield components of both varieties and application of zeolite and calcium silicate decreased the damages of salt stress in some traits. Besides, Zarfam showed better response to the calcium silicate and this treatment was more effective in comparison with zeolite in both canola varieties.

Soil maps are the major source of information for land management, natural resources, and environment. Soil salinity is one of the most important factors limiting crop production in Sistan plain. In this research, geostatistical and random forest methods were compared to produce soil salinity maps. Preparation of accurate maps for soil salinity conditions is of great help in proper management of lands in this area. For this purpose, 460 composite soil samples were collected from 0-30 cm depth in 41000 ha of Zahak region of Sistan plain, using 750 m grid network. Then, the electrical conductivity of saturation paste was measured. Afterwards, 361 samples were used for training and 99 for testing. In the geostatistical model, different semi-variogram including circular, spherical, exponential, and Gaussian and different interpolation methods including inverse distance weighting, ordinary kriging, simple kriging, universal kriging and co-kriging were fitted and the best models were selected. In random forest model, digital soil mapping technique was used and environmental covariates were derived from digital elevation model (DEM) map and A Landsat 8 ETM image. The results of geostatistical method showed that soil salinity had a medium spatial correlation in the study area and the best semi-variogram and interpolation model were spherical and ordinary kriging, respectively. In random forest model, aspect, NDVI, and NDSI were the most important covariate in predicting soil salinity. The results Root Mean Square Error and Mean Error for the training and testing data showed that random forest method was slightly better than geostatistics. The use of other covariates such as land use and soil series maps can increase accuracy of the maps based on random forest methods, thereby improving decision-making. Using other environmental covariates that were not used in this study such as land unit and soil series map can also improve the accuracy of the map.

Cation exchange capacity (CEC) is one of the most important characteristics of soils in relation to nutrient elements and water storage in the soil, as well as soil pollution management. CEC measurement is difficult and time-consuming. So, estimating it by use of soil readily available properties is good. In this study, intelligent model was employed and the parameters used were the physical and chemical properties of the soil such as particle size distribution, organic carbon, clay and sands content, phosphorus, nitrogen, PH and EC. The methods of artificial neural network (MLP), (RBF) and Adaptive-network-based fuzzy inference system (ANFIS) were used to assess CEC. Then, the ability of this method to predict CEC was investigated by using 250 soil samples in two groups: 80 percent for training and 20 percent for validation. To determine the accuracy of the model prediction of CEC, statistical indices including Mean Absolute Error (MAE), the coefficient of determination (R2), and Root Mean Square error (RMSE) were evaluated. The results showed higher efficiency of artificial neural network MLP compared to the other models with the values of MAE, RMSE, R2equal to 1.79, 2.54, and 0.8, respectively1. The sensitivity analysis performed on the input data to the model showed that organic carbon and the pH had the highest and lowest correlation with the cation exchange capacity. The results show that use of artificial neural network to estimate the soil cation exchange capacity is possible and can be used to facilitate the measurement, lower economic cost, and save time.

There are problems in solubility and bioavailability of nutrient elements in soils of Iran because of parent materials and climate. Sulfur oxidation and sulfuric acid production is one of the strategies for overcoming this problem. Many soil microorganisms including Thiobacillus are capable of oxidizing sulfur and thereby decreasing soil pH. In the present study, the effect of sulfur and Thiobacillus was studied for evaluation of some chemical soil characteristics in a factorial randomized complete block design in research fields of provinces of Khorasan Razavi, Fars, Kermanshah, Khuzestan, Qazvin and Kerman (Kerman and Jiroft). The factors including sulfur at levels of 500, 1000, and 2000 kg.ha-1, Thiobacillus at levels of 10, 20, and 40 kg.ha-1 and triple super phosphate fertilizer based on soil testing and 65% of this recommended rate. The experiment was performed both with and without plant. The results showed that the available phosphorous in soil increased significantly in many regions. The amount of sulfur exceeding 2000 kg caused increase in EC in some regions, therefore, we do not recommended sulfur application over 2000 kg.ha-1. The best treatment for this research was application of 500 to 1000 kg sulfur with combination of 10 to 20 kg Thiobacillus and triple super phosphate.According to the results of this study, application of 2000 kg.ha-1 or more sulfur is not recommended, since compared with 1000 kg.ha-1 , it does not only cause soil pH reduction and increase the availability of the elements, but also increases the electrical conductivity.

Any cadmium (Cd) contaminated soil might cause reduction in plants’ yield and increase the hazard of Cd-contaminated plants consumption by both human and animals. The research aimed to investigate the effect of EDTA chelate on Cd uptake in pot marigold (Calendula officinalis L.). A factorial experiment using randomized complete blocks was used in three replications. Treatments included application of 0(C0), 25(C25), and 50(C50) Mg ha-1 cow manure in a Cd polluted soil [ 0(Cd0), 5(Cd5), and 10 (Cd10) mg Cd kg -1 soil] and two rates of EDTA chelate (0 and 2.5 mmol kg-1 soil). Applying 2.5 mmol EDTA chelate caused significant increase in shoot Cd uptake by 21% and 25% in a Cd polluted soil (10 mg Cd kg -1 soil) treated with 25 and 50 Mg ha-1 cow manure, respectively. Also, addition of 2.5 mmol EDTA chelate caused an increase in the root and shoot bio-concentration factor. The results of this experiment showed that applying 2.5 mmol EDTA would increase the Cd availability, which could be considered as a factor that plays an important role in Cd remediation in soils treated with organic amendments.

In many arid and semi-arid countries, population growth and the need for increased food production are forcing the management planners to consider all sources of water to achieve further development. Water quality could affect soil physical, chemical, and biological properties. A laboratory experiment was carried out to study the effect of soil texture and salinity and sodicity of water on some physical and mechanical properties of the soil. Two soils with sandy loam and clay loam textures were treated with twelve waters with different qualities, i.e. combinations of four levels of salinity (EC) including 0.2, 1, 6, and 10 dS m-1 and three levels of sodicity (SARs of 1, 5, and 12), and were subjected to wetting and drying for five times. The consistency limits, plastic and friability indices, dispersible clay and optimum water content in Proctor compaction test were determined. The significant effects of treatments on the determined soil properties suggested that water quality altered the soil microstructure. Effects of salinity and sodicity on clay loam soil were more than sandy loam soil. Unlike the clay loam soil, in the sandy loam soil, the consistency limits did not significantly change as a result of low clay content. At each salinity treatment, the higher the SAR of water, the greater was the impact on soil microstructure; as the plasticity index was increased and friability index was decreased, both might result in undesirable tillage operations. Increase in the calcium concentration at each SAR treatment reduced the dispersible clay and increased Proctor test optimum water content.

Color is one of the fundamental properties of soils that is strongly correlated with other soil characteristics and can be used for investigating soil and land development and chronosequences. To investigate the relationship between soil age and color in the Taleghan area, after primary studies and provision of geological and topographic maps and specifying terrace's boundaries, a total of 13 control profiles were dug and described on the terraces. Then, soil color was quantified with Helms method. For thermoluminsence, dating we collected samples at night and put them in special bags which were sealed to prevent light exposure. In the laboratory under red light TL, samples were prepared for dating using fine grain method and were analyzed using the combined additive and regenerative method. At the end, physico-chemical tests were conducted on the soil samples. Findings of this study showed that the age of soils may vary from 4,650 years to 100,000 years. Also, the results of this research show that the percentages of organic carbon and clay in some soils increase with the increase in the age of the Taleghan terrace. Starting from the lower part towards the upper part, there was a significant difference (p

Soil is one of the most complex parts of environment that ecosystems health greatly depends on its quality. This study aimed to investigate the behavioral differences of Zn and Pb in the presence of humic substances. An experiment was conducted to measure levels of heavy metals (Zn and Pb), 6 levels of initial concentrations (0, 250, 500, 1000, 1500, 2000 mg L-1) in the presence and absence of fulvic acid in a completely randomized design with factorial arrangement. The results showed that, in the absence of fulvic acid, Pb adsorption was greater than Zn, whileits presence significantly (p

Soil water deficits and associated plant water stresses comprise the greatest abiotic hindrance to sustainable plant growth. Supplemental irrigation without water conservation prac­tices is time consuming, and requires additional training. Thus, using new technologies is necessary for optimum water use efficiency. Subsurface water retention technology (SWRT) is a new method which improves characteristics of highly permeable sandy soils. Therefore, this study was established to investigate the effect of the SWRT, mulch, and water quality on height, 1000 grain weight, and yield of maize in an arid region of Kerman, Iran. This field study was performed in a complete randomized block design and factorial arrangement with three treatments: i) depths of polyethylene membrane sheets (without membrane installation, membrane installation at depths of 40, 60, and alternately 40 and 60 cm), ii) application of surface straw mulch (0 and 4 t.ha-1), and iii) irrigation by saline water (1.5 and 3.5 dS.m-1). All treatment plots were put under maize cultivation in June 2013 and 2015. The height of corn at the end of growth and 1000 grain weight and yield were measured after harvest in November each year. Results demonstrated that installing SWRT membranes below plant root zones substantially increased corn growth and production in the sandy soil. The maximum height and yield of corn were observed in the treatment with membrane depth at 60 cm. Based on the results of this research, application of mulch caused increase in yield (33.89 %) in SWRT treatment, while the increase in water salinity level decreased 1000 grain weight (29.13 %), height (15.35%), and yield of corn (33.7%).

Soil pore size distribution (SPSD) is one of the most important soil physical quality indices which reflect soil inherent characteristics and its management system. The soil water integral energy (EI) is an index that represents the amount of energy needed to uptake a mass unit of soil water by plants. In this research, we studied the effects of SPSD curves location and shape parameters on EI index of different soil water ranges in medium to coarse-textured soilsof Torogh Agricultural and Natural Resources Research and Education Station in Khorasan-Razavi province. Thirty points with different soil textures and organic carbon contents were selected. After conducting required laboratory and field measurements using standard methods, the soil moisture release curve (SMRC) parameters, the SPSD curve parameters, plant available water (PAW) and least limiting water range (LLWR) which were measured in matric heads of 100 and 330 cm for the field capacity, integral water capacity (IWC) and EI of the mentioned soil water ranges were calculated and the relationships between the SPSD curve location and shape parameters and EI values (for PAW100, PAW330, LLWR100, LLWR330 and IWC) were statistically analyzed. The results showed that, in medium to coarse-textured soils, increasing the equivalent pore diameter and reducing the diversity of soil pore sizes along with the tendency of the SPSD curves to be more peaked in the center and more tailed at the two ends compared with lognormal distribution could lead to lower EI and easier uptake of water by plants in different soil water ranges.