نشریه پژوهشهای خاک (علوم خاک و آب)
سال سی و سوم شماره 3 (پاییز 1398)

Olive is one of the most important agricultural products in Qazvin Province, which has the second highest production in Iran. However, unbalanced fertilization is the main reason for disruption and disturbance in the nutritional balance and low yield in olive orchards. Increasing the yield is possible if there is a balance between the nutrients in the plant. In order to optimize the use of fertilizers and to diagnose nutritional disorders, the use of nutritional indices seems to be necessary. This study was conducted in 80 olive orchards in Tarom city in Qazvin province (Iran) for three years. Soil and leaf samples were taken and analyzed as the standard method. In September, harvesting was performed and yield was measured. Then, the nutrient indices for the orchards were determined by Compositional Nutrient Diagnosis (CND) and Deviation from Optimum Percentage (DOP) diagnosis methods. Based on the average calculated yields by both methods, the studied orchards were classified into two groups of high and low yields. The average optimum concentration of nutrients (reference numbers) for nitrogen, phosphorus, potassium, calcium, magnesium, manganese, zinc, copper, and boron was obtained by both methods and the results of the DOP and CND indices were compared. The DOP and CND indices showed a deficiency of Mg, N, and Ca in most of the studied orchards. Generally, according to the studied indices, all orchards with low relative yield were in unbalanced conditions in terms of nutritional elements.

In this study, the pollution status and horizontal distribution of heavy metals of Ni, Cd, Pb and Zn was investigated along the Arak-Qom highway in an agricultural field under alfalfa. Soil samples from depths of 0-10 and 10-20 cm were collected perpendicular to the road at the distances of 0, 50, 100, 150, 200, 250 and 300 m. The content of the total and available levels of these heavy metals was investigated as a function of distance from the road and soil depth. Results showed that the total and available concentration of heavy metals decreased by increasing distance from the road, indicating that accumulation of heavy metals in top soils was greatly influenced by traffic. Also, organic matter content and pH decreased with distance from the roadway, probably due to the presence of vegetation on the surface and accumulation of organic matter including debris such as paper, plastic and hydrocarbons (garbage out of vehicles). The concentration of measured heavy metals were higher than standard (FAO/WHO) and in layer of 0-10 cm were higher than 10-20 cm. The mean total concentration of heavy metals of Ni (109.60), Cd (47.11), Pb (553.41) and Zn (241.95) all in mg kg-1 followed the order of Pb> Zn> Ni> Cd. In terms of geo-accumulation index and contamination factor for Ni, Cd and Pb, the soil showed high levels of contamination, as the geo-accumulation index for Ni, Cd and Pb were 6.75, 6.71 and 4.21, and the contamination factors were 161.18, 157.02 and 27.67, respectively,which suggests care must be taken to control the level of heavy metals concentration on roadside soils as these soils are often cultivated to produce food crops.High accumulations of heavy metals were usually found on alfalfa and accumulation of the heavy metals was higher in shoot than root. Median values of Ni, Cd, Pb and Zn were 29.44, 15.64, 5.79 and 10.50 mg kg-1 for root and 47.98, 19.77, 7.14 and 13.53 mg kg-1 for shoot, respectively. Results show that it is necessary to have continuous studies on the accumulation of heavy metals and the potential ecological risk assessment to ensure effective protection and management of urban soil and other environmental media.

Considering the importance of wheat in human nutrition and the presence of high concentrations of heavy and toxic metals in contaminated lands, it is important to study the effect of zeolite and composted cow manure and their role in reducing soil contamination and wheat nutritious properties. For this purpose, a factorial experiment was conducted based on a completely randomized design with three replications. The treatments included different amounts of zeolite and compost, each with zero, 0.5%, 1%, and 1.5% based on the weight percentage of soil. The results showed that the effect of zeolite, composted manure, and their interaction on cadmium, nitrogen, phosphorus and potassium in root, stem, and seed were significant at 1% level. The maximum cadmium in different parts of plant was obtained in non-application of zeolite and compost, and the minimum was obtained in 1.5% zeolite and 1.5% compost, with significant differences. The maximum concentrations of nitrogen, phosphorus and potassium in root, stem, and seed were obtained in 1.5% of zeolite plus 1.5% compost, and their minimum concentrations were in non-application of zeolite and compost, with significant differences. In general, the results of the experiment showed that application of zeolite and compost to cadmium-contaminated lands could reduce absorption of cadmium, and the damage caused by it, and could increase absorption of essential elements.

Nowadays, recycling of organic wastes produced in food and medicinal factories by applying them to agricultural lands as organic fertilizers is the focus of attention. The present study was carried out to compare the effect of applying organic wastes of four factories in Fars and Khuzestan provinces and their biochars on some of the chemical properties of a calcareous soil. An experiment was conducted for two months in a completely randomized design based on a factorial arrangement (9 × 4), including 9 organic waste types (filter cake, bagasse, bagasse-biochar, sugar beet, sugar beet-biochar, licorice, licorice-biochar, soybean meal and soybean meal-biochar) at 4 rates of application (0, 1%, 2% and 3% by weight) with three replications. The results showed that interaction effects of organic waste types and rates, on the soil available phosphorus (P), soil DTPA-extractable iron (Fe), copper (Cu) and manganese (Mn) concentrations and electrical conductivity (EC) were significant. The soil amended with soybean meal had the highest nitrogen (N) and Cu content. Filter cake was a good source for P, zinc (Zn) and Fe and sugar beet pulp was a good source for Mn. There was no significant difference in the amounts of available nutrients between raw organic materials and their biochars. Although the increase in the level of application of these wastes by two to three percent by weight increased the accessibility of these elements, the application of higher levels of these wastes was accompanied by 33% to 166% increase in soil electrical conductivity; so, widespread use of these wastes should be done more cautiously.

To study manganese (Mn) status and its effect on fruit yield and quality of Thomson navel oranges, two separate experiments were carried out in East of Mazandaran Province, Iran. The first experiment was conducted in citrus orchards of the region, and the second was conducted in an orchard of Thomson navel on sour orange rootstock, using a randomized complete block design with seven treatments and four replications. Treatments included: 1) First control (without manganese); 2) Second control (without manganese and with urea spray), 3) 300 g manganese sulfate per tree as soil application, before leaf development, 4) 300 g manganese sulfate per tree as fertigation, in the first stage of fruit growth, 5) 300 g manganese sulfate per tree as fertigation, in the first and second stages of fruit growth, 6) Manganese sulfate spraying in the first stage of fruit growth, and 7) Manganese sulfate spraying in the first and second stages of growth. The results showed that the orchards of Sari and Neka had the most deficiency symptoms. The results of the second experiment showed that soil application before leaf development had no effect on yield, fruit quality, Mn concentration in leaf, fruit and root, but its application as fertigation and spraying increased fruit yield, diameter, and weight, leaf and fruit manganese concentration. The highest leaf Mn concentration was obtained from the first and second stage of fruit growth treatment. Fertigation treatment significantly increased the root Mn concentration compared to the control. In general, according to the results of this experiment, for orchards with a history of mild manganese deficiency or probable manganese deficiency, application of manganese sulfate as fertigation or spray after the fall of petals in the first stage of fruit growth is recommended. However, for orchards that have severe symptoms of manganese chlorosis, two foliar applications or fertigations with manganese sulfate, after petal fall and second stage of the fruit growth, before the growth of the fall flash, is recommended.

Distinguishing soil surface horizon and its thickness is possible through soil survey and drilling. This requires budget, time, and skilled persons; therefore, using predicting methods as a solution for simple determination of soil characteristics has gained much importance in recent years. This work considers employing stepwise multiple linear regression statistical approach in order to propose a suitable model to predicate soil surface horizon thickness (SSHT) from topographic attributes according to establishment of soil and landscape characteristics relationships. To fulfill the goals of this study, data of primary and secondary topographic features of the Rimeleh sub-catchment located in Lorestan Province of Iran were derived from a Digital Elevation Model (DEM) and, the SSHT data yielded from soil surveys at 191 sampling points distributed in the study area in a systematically randomized manner. The SPSS 19 package was used to clarify statistical characteristics of gathered SSHT topographic data and test the fitted model considerations. The fitted model for the gathered data was Athick = 39.596 – 0.012E – 0.152S + 0.008AS.  The determination coefficient of the model was computed as 0.54. It is clear that the model fitted to the data has highly significant negative correlation with slope percent (S) and elevation (E) (P≤0.01) and a significant positive correlation with aspect (AS) (P≤0.05). Our investigation demonstrated that the fitted model to the scatter plot of observed data values versus predicted values has a determination coefficient of 0.54, which indicates the explanatory power of the model. Other topographic attributes affected the SSHT but their effects were not significant statistically. Therefore, they were not included in the model.

An important issue in some citrus varieties including Satsuma mandarin is alternate bearing. Therefore, to reduce alternate bearing in Satsuma mandarin trees, an experiment was conducted as randomized complete block design with 4 treatments and 4 replications. The experiment was done during 7 years with 32 Satsuma mandarin trees which were almost the same age and size. The experimental treatments of nitrogen use management included T1= Control (three splits, the first split late in March, the second late in April after fruit formation, and the third one month after the second split); T2= Summer application (15% before flowering, 30% after fruit formation, 20% at the time of physiological drop, and 35% after the beginning of fruit development); T3= Autumn application (15% before flowering, 30% after fruit formation, 30% at the time of physiological drop and 25% after fruit harvest); T4= Summer and autumn application (15% before flowering, 30% after fruit formation, 20% at the time of physiological drop, 20% after starting development, and 15% after fruit harvest). Results showed that fruit yield had the greatest difference in the first and second years of experiment and then the yield difference gradually decreased. The lowest cumulative yield (379  kg/tree) was obtained from the control and the highest cumulative yield (446 kg/tree) was obtained from summer and autumn N treatment. Results showed that the control had the highest alternate bearing index (0.40) and autumn N application treatment had the lowest treatment index (0.18). Also, year had a significant effect on fruit average weight as the highest fruit average weight was obtained in the fifth year. In all N application treatments, fruit average weight was significantly more (at 5% level) than the control. Based on the results of this study, to minimize alternate bearing, the time and amount of nitrogen fertilizers are recommended in the following four stages: 15% at the beginning of flowering, 30% between fruit set and the beginning of June drop; 30% at the beginning of June drop to early phase of the second growth of fruits; and 25% after fruit harvest.

In order to investigate the effects of application of sodium chloride, organic matter, and growth promoting bacteria on fresh and dry shoot weights and also concentration of some nutrients in aerial parts of spinach, a factorial experiment was conducted in a completely randomized design with three replications.  The treatments consisted of three levels of sodium chloride (control (S0), 2 (S2) and 4 (S4) g Na Cl kg-1 soil equivalent to 0.7, 8 and 16.8 dS/m, respectively), five levels of organic matter (control 0%(OM0), 0.5% (RS0.5) and 1% (RS1) % rice husk and 0.5% (Bi0.5) and 1% (Bi1) % rice husk biochar, w/w)  and two bacterial levels i.e. without (P0) and with bacteria (P1). Results showed that increasing salinity levels significantly increased spinach dry weight, but significantly decreased concentrations of N, P, Ca and Mg in aerial part, while concentration of Na increased. With the use of organic matter sources, fresh and dry weights of spinach shoot and con fluorescence [H1] centration of all nutrients increased significantly. Also, addition of Pseudomonas fluorescence significantly increased fresh and dry weights and concentration of nutrients of spinach aerial part .According to the results obtained in this study, it can be concluded that the use of organic matter as a soil amendment and rich source of nutrients can greatly increase concentration of nutrients in spinach. Also, addition of Pseudomonas fluorescence as a biofertilizer can improve spinach growth and increase concentration of some nutrients in spinach aerial part under salinity conditions. Application of organic matter and bacteria in salinity-free conditions increased concentration of nutrient and yield of plant. In general, further investigations under field conditions are necessary to verify the results of the present study.  [H1]?

This research was carried out to compare the methods of determining the spatial distribution of soil organic carbon and nitrogen on 50,000 hectares of Lenjanat area in Isfahan province, central Iran. The spatial distribution of elements was determined by Ordinary Kriging, Inverse Distance Weighting, and Spline Tension interpolation methods. The results indicated that there was an average spatial structure in the variables. Empirical variograms showed that there was no specific anisotropy process for variables. In order to determine the accuracy of the estimation of interpolation methods, the standard data (150 data for each variable) and statistical criteria including Mean Estimation Error (MEE), Mean Square Estimation Error (MSEE), Root Mean Square Error (RMSE), relative Error (Er) and Pearson correlation coefficient (r) were used. Despite the high spatial variability of the parameters, the results indicate the accuracy of the estimated values by means of interpolation methods. For soil organic carbon in the study area, Ordinary Kriging and Spline Tension interpolation methods with lower error (MEE= 0.007, MSEE= 0.09, RMSE= 0.3, Er= 0.32 and r= 0.73) were more accurate compared with the Inverse Distance Weighting interpolation method (MEE= 0.009, MSEE= 0.096, RMSE= 0.31, Er= 0.31 and r= 0.71). Also, Ordinary Kriging and Inverse Distance Weighting interpolation methods with a lower error (MEE= 0.003, MSEE= 0.0006, RMSE= 0.025, Er= 0.296 and r= 0.8), compared with Spline Tension interpolation method (MEE= 0.0017, MSEE= 0.0007, RMSE= 0.026, Er= 0.301 and r= 0.78) had more accurate estimation of soil nitrogen in the region.

Soil pollution with heavy metals has become a global concern because of its damaging effects on the environment, including threats to human health, toxicity in plants, and long-term effects on soil fertility. This study was conducted to investigate the effect of organic amendments (biochar 640°C, and biochar 420°C) and inorganic amendments (Pumice, Leca, Zeolite and Bentonite) andincubation time on the chemical forms of Pb in a contaminated calcareoussoil. Treatments consisted of two incubation times (90 and 180 days) and three amendment levels (0, 1, and 5 wt%). The experiment was conducted in a factorial arrangement with completely randomized design, with three replications.  At the end of the incubation times, the chemical fractions of Pb were determined by Tessier sequential extraction method. The experimental resultsindicated that application of amendments effectively decreased the Pb concentrations in the exchangeable fraction (F1) of contaminated soils. The 5% biochar 640 showed the highest decrease in the F1 fraction of Pb. The results showed that Pb concentration increased the exchangeable (16.52%), carbonated (1.02%), oxide (9.53%), and residual (2.1%) fractions and decreased the organic fraction (15.26%) during the time. With the passing of time, treatment with Biochar 640°C and bentonite (5%) was the most effective in decreasing Pb concentration in exchangeable fraction.

Infiltration modeling in unsaturated zone is usually based on the numerical solution of Richards equation. Complexity in numerical solution, disregard of parameter’s uncertainties, and difficulty in application of this model at large scale attracted the attention of researchers to other approaches. In this research, a rule-based fuzzy model for infiltration in the soil matrix is presented. The rules were derived from a large generated training sets obtained by numerical solution of Richards equation by using Hydrus model. Forty-nine fuzzy rules based on 7 moisture classes were applied in fuzzy model. Fuzzy rule based model could simulate flux in any time step, and by using continuity equation could calculate moisture in any depth in soil profile. Results showed good accuracy for both flux and moisture predictions for loam, sand, and silt soil textures in any time steps (average NRMSE =3.84). Model performance had the best result in saturated zone and a poor result for wetting front. Because of duplicate process of calculating moisture in any time step and replacing it as an initial moisture for t+∆t time step, mass balance could prevent cumulative error for the large time steps.