نشریه تحقیقات کاربردی خاک
سال چهارم شماره 1 (تابستان 1395)

Root stabilization of heavy metals (HMs) by glomalin is one of the protective mechanisms of mycorrhizal fungi in response to metal stress. Considering this hypothesize, the contribution of Rhizophagus irregularis in symbiosis with white clover (Trifolium repens L.) to root stabilization of Cd, glomalin production by the fungus, and Cd sequestration was investigated. A pot culture experiment was conducted as completely randomized block design by two factors including arbuscular mycorrhizal fungus (inoculated with R. irregularis and non-inoculated) and four levels of Cd (0, 15, 30 and 45 µM) with five replications. The results showed that the root colonization by R. irregularis improved phosphorus nutrition, shoot and root dry weights compared to the non-mycorrhizal plants. With increasing of Cd concentration, plant uptake and extraction efficiency of Cd increased but Cd translocation efficiency decreased. Uptake efficiency of Cd in mycorrhizal plants was higher than non-mycorrhizal ones. Translocation efficiency of Cd in mycorrhizal plants was lower than non-mycorrhizal ones, although this factor showed no significant difference between mycorrhizal and non-mycorrhizal plants. Moreover, Cd uptake by roots was higher than shoots and this portion in mycorrhizal plants was higher than non-mycorrhizal ones. Therefore, mycorrhizal clover plants had higher contribution to root stabilization of Cd. Glomalin production and its Cd sequestration capacity was significantly increased as Cd concentration increased. As a result, higher contribution of mycorrhizal roots to Cd uptake can be due to sequestration of Cd in fungal structures inside the roots. Consequently, glomalin could be considered as an induced-stress protein as well as a vital and effective component of spore and hyphal cell wall of the fungus. Glomalin as a heat shock protein, has important role in Cd root stabilization via protection of host plant from toxic effects of Cd and reduction of the Cd bioavailability.

In this study, the effects of wheat straw on physical quality indices of two sandy loam and clay loam soils were compared. Factorial experiment was conducted as a randomized block design at 4 replicates. The first factor was straw used rates at 5 levels including 0, 1, 2, 3 and 5 mass percent; the second factor was 2 soil textural classes. Soil columns were incubated at the temperature of 22±4 °C and moisture of 50 to 75 percent of field capacity for 6 months then soil properties measured at the end of sixth month. The α and n parameters of van Genuchten model using RETC software, pore size distribution and Dexter Sp value using soil moisture curve data were calculated. Application of straw at the rates of 1 to 5%, significantly increased mean weight diameter (MWD) of aggregates from 87.5 to 358.3 and 27.87 to 104.92%, saturated hydraulic conductivity from 22.94 to 195.41 and 80 to 162.58%, available water capacity (AWC) from 16.27 to 105.7 and 10.94 to 96.35%, n parameter from 4.5 to 21.8 and 1.74 to 8.14% and Sp from 32.61 to 73.91 and 5.62 to 38.2% and decreased α parameter from 12.67 to 59.15 and 25 to 45% in sandy loam and clay loam soils, respectively. Consequently, improving effects of straw at the used rates on the sandy loam soil was more observable than clay loam soil.

Iron is one of the essential micronutrients for plants. The various components of soil elements differ significantly from each other in terms of reactivity and bioavailability. The purpose of this research was to study the distribution of different forms of Iron among the various soil components and the relationships between the metal components with some soil characteristics. So, an experiment was carried out on 10 samples collected from different areas of Golestan province with different chemical and physical properties. Fractionation of soil iron was determined via Singh et al (1988)’s sequential extraction procedure. For investigating the relationship among the various forms of soil iron with dry matter, concentration and uptake of iron, a factorial pot experiment on Glycine max cv. Williams in a completely randomized design (10 types of soil at first factor and two iron fertilizer levels (0 and 20 Fe mg kg-1) at second factor), with three replications was also conducted. The results showed that the amounts of iron chemical forms were ordered as follows: carbonates-bound

Direct measurement of soil physical properties is time consuming, costly and sometimes unreliable because of soil heterogeneity and experimental errors. Stability of aggregates could be estimated from surrogate data such as soil texture, bulk density, organic carbon and CaCO3 using pedotransfer function (PTF).The objective of this research was to present regression PTFs and artificial neural network models to predict mean weight diameter (MWD) of aggregate from limited sets of soil properties and to assess the efficiency of the presented models to predict the MWD with the statistical criteria including the coefficient of determination (R2) and root mean square deviation (RMSE). In total, 100 soil sample were collected from Ardabil plain and analyzed for their physicals and chemicals properties. Soil samples were divided into two groups, so that, 80 samples were used for the development and remaining 20 samples for the validation of PTFs. The values of R2 and RMSE for regression PTFs and artificial neural networks were, respectively, 0.88, 0.42 for neural networks and 0.81, 0.054 for regression PTF. Results showed that two methods could be applied to predict the MWD in Ardabil plain. However, artificial neural networks performed better than regression model in this study.

Lead (Pb) is one of dangerous environmental contaminated factors which threaten the health of plants, animals and humans. Lead in the soil led to reduce the biological activities of soil. The aim of this study was to evaluate the effect of vermicompost (C) of apple pruning wastes on microorganism’s activity of a Pb-contaminated soil. For this purpose an experiment was carried out in greenhouse condition as a factorial experiment based on a randomized completely design with two factors including Pb concentration in four levels (0, 250, 500 and 1000 mg Pb kg-1 soil) and vermicompost in three levels (0, 20 and 40 t ha-1). A soil sample was selected and spiked uniformly with different concentrations of Pb. These samples were incubated for 90 days, and then some biological experiments were measured. Results showed that by increasing the Pb concentration in soil, BR, SIR and MBC were reduced intensively, but these indices were improved by adding the vermicompost. Using 20 and 40 t ha-1 vermicompost increased BR up to 1.95 and 2.33 times higher than control treatment, respectively. MBC at 40 t ha-1 vermicompost application treatment on average was 3.18 times higher than control treatment. The amount of qCO2 increased up to 2.6 times in C20 (20 t ha-1 vermicompost) treatment compared to control. Therefore it could be concluded that application of vermicompost ameliorate the toxic impacts of Pb on microorganisms activity.

Soil salinity is a serious environmental problem especially in arid and semiarid areas. Therefore, it is vital to generate and update soil salinity maps in order to determine early stage of salinization. Electromagnetic induction instrument is an alternative to traditional methods for assessing soil salinity. Different methods have been used to calibrate electromagnetic induction instrument. At present research, an attempt was made to calibrate EM38 in pistachio orchard located in Ardakan city using multi-linear regression (MLR), artificial neural network (ANN) and neuro-fuzzy (ANFIS). To calibrate and predict soil salinity in nine standard depths, the best result was obtained by ANFIS model with R2 of 0.06, 0.11, 0.30, 0.59, 0.69, 0.64, 0.70, 0.74 and 0.74; and RMSE of 4.09, 3.66, 2.87, 2.22, 2.26, 2.62, 2.46, 2.38 and 2.50, respectively; which showed the accuracy of ANFIS was higher than other models (ANN and MLR) to predict soil salinity and calibrate EM38.

Iran stands 2nd in the world in watermelon production and export. Kerman province, in southeast of Iran, ranks 1st in the country, but in the recent decade, some factors including drought, soil physical and chemical properties, low quality of irrigation water and lack of optimum and balanced nutrient use has resulted in reduction of quantity and quality as well as blossom end rot (BER) rise in this product. Therefore, an experiment was conducted to assess simultaneous effects of organic matter, potassium and calcium on yield, chemical composition and BER severity of watermelon that is a new study in the region. The experiment was accomplished as factorial in a Randomized Complete Block Design (RCBD) in one of the southeast towns of Iran. Experimental treatments were comprised of organic matter in two levels (0 and 20 ton ha-1 of farmyard manure), potassium sulfate fertilizer in three levels (0, 250 and 350 kg ha-1) and foliar spray of calcium chelate in two levels (0 and 4 g l-1). The results showed that organic matter application and foliar spray of calcium chelate increased yield, calcium, iron and zinc concentration of plants, whereas the severity of BER was declined. Potassium sulfate application caused yield increase, but the rates more than 250 kg ha-1 resulted in reduction of plant calcium, zinc and iron concentration and higher rate of BER.

Because of the effect of heavy elements on food chain, monitoring the concentration of these elements, especially cadmium (Cd) in soil, water and plant system is vital. Vermiwash is materials which excreted from the earthworm body and is rich in vitamins, hormones, enzymes, macro- and micronutrients which can help plants to efficient growth. To study the effects of vermiwash on growth and concentration of Cd and micro elements in a Cd contaminated soil by Spinach (Spinach oleracea) an experiment was conducted for 8 weeks. The experiment was on basis factorial randomized complete design and with 2 factor that including vermiwash in four level (0, 25, 50, 100 ml kg-1 soil) and cadmium in four level (5, 10, 20, 40 mg kg-1 soil) which had been done in greenhouse of Zabol University. Results showed that vermiwash has an effective role in improving growth and yield of spinach, and minimum and maximum spinach fresh (33.6 g) and dry (3.91g) weight obtained in control (without vermiwash) and 40 mg kg-1 Cd and 50 g kg-1 vermiwash and 5 mg kg-1 Cd, respectively. Concentration of Fe, Zn and Cu as well as total uptake were increased with increasing vermiwash in all Cd concentrations. Also maximum organic matter in soil was obtained in 100 ml kg-1 level vermiwash which showed significant differences with control. The finding of this research also shows that vermiwash has not significant effect on Mn and Cd Concentrations.

The availability of some nutrient elements in many soils of Iran is low because of high pH values. Therefore, any strategy for solution of this problem is important. This study carried out to evaluate the possibility of sulfur-bentonite application and Thiobacillus neapolitanous inoculation on corn (Single Cross 704) growth as factorial field experiments in Mashhad, Kermanshah, Qazvin and Dezful regions. The treatments were sulfur (control, 500, 1000 and 2000 kg ha-1) and triple super phosphate (control, 65 and 100% of recommended based on soil testing). The results revealed that sulphur, phosphorous and their interaction increased significantly corn shoot dry and wet weight. The sulfur application compared to control, significantly increased corn wet and dry matter. There was no significant difference between 1000 and 2000 kg S ha-1, but these levels showed significant difference with 500 kg S ha-1. All of the sulfur levels increased significantly the Fe uptake compared to the control, however, no difference observed between 500 and 1000 kg S ha-1, while application of 2000 kg sulfur resulted to the highest Fe uptake. The best treatment increased corn yield by 61, 9.8, 16.8 and 17.9 % in Mashhad, Qazvin, Kermanshah and Dezful respectively. Iron uptake increment at mentioned regions were 2%, 43%, 16.6% and 22.6%, respectively.