Iranian Journal of Soil Research
Year:2021 | Volume:34 | Issue:4|Papers Count:9

Developing an appropriate methodology to evaluate soil quality is urgent and has great implications in sustainable agricultural production. This study was carried out with the aim of determining the minimum data set (MDS) for soil quality evaluation and the comparison of soil quality evaluation methods in tea cultivation with different productivities in west Guilan province. Sixty-six soil samples were collected from 0 to 30 cm depth. The green tea leaves were harvested at a 2 m2 plot at each site. In this research, using the principal component analysis (PCA) method, among 15 physical, chemical and biological soil indicators as total data set (TDS), available potassium, organic carbon, pH, available phosphorus, available zinc and nematode were determined as the MDS. Then, the soil quality of tea cultivation with different productivities was evaluated by Integrated Quality Index (IQI) and Nemoro Quality Index (NQI) using two linear and non-linear scoring methods (LS and NLS) and two soil indicator selection approaches, a Total Data Set (TDS) and a Minimum Data Set (MDS). The results showed that all mean soil quality indices of the high productivity tea cultivation except IQI-NLSMDS and NQINLSMDS were significantly higher than low productivity tea cultivation. It was found that linear scoring methods are superior to non-linear. So that, the correlations between soil quality indices and crop yields for the IQI-LS and NQI-LS methods were Stronger than in the other methods in both TDS (R2=0. 55 and 0. 54, respectively) and MDS (R2=0. 45 and 0. 46, respectively). The correlation between TDS and MDS evaluated by the IQI– LS (R2=0. 80) were higher than that by NQI– LS (R2=0. 59).

Soil tests play a very important role in management of nutrients in the field. The efficiency of a soil test result depends on extractant suitability for determination of available nutrient. Also, for calibration of each nutrient in the soils of a specific region and plant, a critical limit should be determined so that the soil test for each element can be the basis of fertilizer recommendation. Bean (Phaseolus vulgaris L. ) is important agricultural product due to high protein. Due to the lack of relevant information in this field, this study was conducted on bean soils in Markazi province. 30 samples of surface soil (0-30cm) with a wide range in terms of available potassium, as well as physical and chemical properties were selected from the bean cultivation soils of the Markazi province and after preparing soil samples in the greenhouse, beans were planted in them. In order to evaluate the response of bean to potassium fertilizer application, two levels of 0 and 100 mgKkg-1 were used as potassium sulfate in this experiment. The greenhouse experiment was performed in a completely randomized design with three replications. At the end of the growing season, harvested plants and plant responses including dry matter weight, potassium concentration and uptake, and relative growth were determined. Six extractants including distilled water, hydrochloric acid 0. 13M, nitric acid 0. 5M, calcium chloride 0. 025M, Olsen and ammonium acetate 1M were evaluated to extraction of available potassium. The results of analysis of variance showed that the main effects of soil and potassium fertilizer were significant (p<0. 01) on dry matter weight, potassium concentration and uptake. But the effect of soil and fertilizer interaction was significant only on plant potassium concentration. Comparison of the mean showed that the effect of potassium fertilizer application were significant on plant responses. The results of correlation coefficient of different extractants with plant responses showed that ammonium acetate (1M) had a positive and significant correlation with plant potassium concentration (0. 67**) and uptake (0. 63**) while other extractants did not show a significant correlation. Using the Cate and Nelson visual method, the potassium critical level was obtained 150 mgkg-1 soil by extracting with ammonium acetate. Dry matter weight had a positive and significant correlation with available potassium concentration, cation exchange capacity, clay and sand. Plant potassium concentration and uptake had a positive and significant correlation with available potassium concentration (r=0. 555**) and soil organic carbon (r = 0. 620*).

1Threshold friction speed is an important factor for assessing the soil erodibility, but its measurement is time consuming and costly. Estimating threshold friction velocity by use of soil reflectance increases operating speed and reduces cost. The aim of this study was to compare the efficiency and accuracy of partial least squares regression (PLSR), support vector regression (SVR) and artificial neural network (ANN) regression models in estimating the threshold friction velocity in dust-prone areas of Khuzestan Province. For this purpose, 91 soil samples were collected from the central and southern parts of dust-prone areas of the province and the threshold friction velocity was determined using wind tunnels. Then, the reflectance spectra of soil samples were obtained with a spectrometer. Pre-processing methods were performed on the main spectrum and modeling was performed using, PLSR, SVR and ANN models. The results showed that the threshold friction velocity in the region was 9. 7 m/s and the minimum was 5. 25 m/s. Also, the threshold friction velocity was significantly (p<0. 05) correlated with dissolved sodium (r=-0. 58) and sodium adsorption ratio (R=-0. 48). The ANN model had the best estimation accuracy in the second derivative preprocessing (PRD = 2. 52) and the SVR model had the lowest estimation accuracy in the main spectrum (PRD = 0. 56). Finally, the key wavelength of the threshold friction velocity was in the range of 1850 and 1930 nm. Because of the soil reflectance correlation with threshold friction velocity (r=0. 76), the spectroscopy method can be used to assess the soil erodibility in areas prone to dust production.

Nowadays, soil salinization is one of the world’ s major threats that reduce soil productivity by intensifying the process of desertification and land degradation. Since laboratory analysis is mostly time consuming and costly, especially in large scales, attempts have been made to study soil salinity using remote sensing techniques in recent years. The present study assessed the potential of remote sensing in predicting soil surface salinity in the east of Lenjan City. Salinity reference points were identified based on analyzing 50 randomly selected surface soil samples. Satellite indices including DVI, NDVI, EVI, MSAVI, SAVI, RVI, NDWI, SI1, SI2, SI3 and SBI were derived from a Landsat-8 satellite image (path and row of 164 and 37) acquired on September 13, 2019. These indices along with three topographic indices of elevation, slope and topographic wetness index (TWI) were introduced to the Multiple Linear regression and Random Forest models. The linear regression model was built using band 6, RVI, NDVI, elevation and TWI with a p-value of 0. 049. In the Random Forest model, band 7, slope, band 5 and elevation were among the most important parameters. The r2 value of this model was 0. 21. The results of this study showed that topographic indices had also great importance in salinity prediction. Moreover, comparison of the results indicated that Random Forest had a higher accuracy than the regression model for determining salinity in the study area.

Conversion of sewage sludge (SL) to biochar is one of the methods that can convert this material into a useful product in agriculture. Heavy metals are present in various forms in SL, which largely determine their bioavailability. Converting SL to biochar can alter the bioavailability of heavy metals. The aim of this study was to compare the effect of SL and its biochar on the availability and fractionation of lead (Pb) in a contaminated calcareous soil (100 mg. kg-1 pb as solution added to soil and incubate for 2 weeks). The contaminated soil was treated with 0. 5%, 1%, and 4% of SL and biochar prepared at temperatures of 400 and 600 ° C. This research was performed as a factorial experiment in a completely randomized design with three replications. After one week of incubation; EC and pH, soluble and available Pb, as well as Pb fractionations in the soil samples were studied by the Tessier method. The results showed that the EC of the soil increased in all treatments compared to the control. pH decreased in SL treatment (1. 3% to 5. 5%) and increased in biochar treatment at both temperatures. The highest increase was observed in the treatment of 4% B600 (5. 97%). The total amount of Pb increased in all treatments, the available Pb in SL treatment increased (8. 2% in 4% treatment) and decreased in biochar treatments (7. 6% in 4% B600 treatment). Application of biochar compared to SL changed the fractionation of Pb from the bioavailability to more stable forms. The highest increase in Pb content compared to the control was bonded to the organic matter fraction (43. 4% to 80. 4%). The results of this research showed that, due to increased pH, specific surface area, or change in surface functional groups, biochar can re-distribute Pb fractions and reduce Pb availability in soil.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants with teratogenic, mutagenic and carcinogenic potential, which can pose potential risks to the environment and human health. Therefore, this study was conducted to detect and assess the potential ecological risk of PAHs in surface soils in the vicinity of Arad-Kouh Processing and Disposal Complex, Tehran, Iran, in 2020. In so doing, 30 surface soil samples were collected from 10 sampling sites adjacent to the Arad-Kouh complex. After extraction of analytes, the gas chromatography/mass spectrometry (GC– MS) method was used for determination of 16 PAHs in the samples. The results showed that the total concentrations of 16 PAHs (Σ 16PAHs) ranged from 863 to 1384 μ g/kg with an average of 1123 μ g/kg. Moreover, Chy and B(ghi)P showed no potential ecological risk, while other PAHs had a moderate potential ecological risk. Also, as computed values of RQΣ PAHs(MPCs for all the sampling sites were lower than 800, the total ecological risk of PAHs in surface soil samples of the study area was classified in the moderate-risk2 category. Based on the results, although the mean concentrations of B(a)A and B(ghi)P were higher than MPC established by Iranian Department of Environment, the mean concentrations of all of the 16 PAHs were lower than MPC established by MHWS. Overall, since PAHs have adverse effects on human health, detection and determination of concentration, source identification, and also periodical monitoring of these compounds in the environment is recommended in order to safeguard human health maintenance.

In order to evaluate the effect of zinc, sulfur inoculated with Thiobacillus, and salinity caused by sodium chloride on some growth parameters and uptake of phosphorus, potassium, and zinc by rapeseed, a greenhouse experiment was conducted in factorial randomized complete block design with three replications. Treatments consisted of soil salinity at four levels (1, 4, 7, and 10 dS m-1), sulfur inoculated with Thiobacillus at two levels (0 and 500 kg ha-1) and zinc sulfate at three levels (0, 25, and 50 mg kg-1). The results showed that salinity stress affected all studied traits and caused a significant reduction in growth parameters such as plant height, root length, shoot and root dry weight, and reduced nutrient uptake; however, salinity caused a significant increase in the roots and shoots sodium concentration. Application of sulfur along with 25 mg kg-1 zinc under salinity stress improved growth traits and increased the concentration of phosphorus, potassium, and zinc by 15. 26%, 110. 5%, and 376. 6%, respectively, and reduced the concentration of sodium in the aerial part of the plant by 34. 77% as compared to the control treatment. In general, the results showed that the use of sulfur inoculated with Thiobacillus and the optimal level of zinc sulfate fertilizer (25 mg kg-1 soil) affected soil properties as well as the direct supply of macro elements; consequently, the amount of nutrient uptake increased under salinity stress and harmful effects of salinity on plants was mitigated by reducing sodium uptake.

The effect of four different two-year rotations (cereals, fallow, clover, and sugar beet, in rotation with cereals) and four different plant nutrition managements (no fertilizer, chemical fertilizers, organic manure and combination of the latter two) was tested during 1958-61, at Karaj Research Center, Iran. Results indicated that although fallow and clover resulted in higher production of barley, as the following crop, further study would be required to check the economic value of these treatments. Such a research has to consider the ease in the availability of chemical fertilizers. The highest yield was obtained from the application of chemical fertilizers at rates of 60, 75, and 60 kg/ha N, P2O5 and K2O, respectively, and organic fertilizer (20 tons animal manure/ha), but it has to be noted that animal manure and other organic materials are not easily available for large-scale application. Although fallow resulted in 30% increase in production of cereals in 1961, reliability of such an effect needs further investigation. The effects of the interactions between rotations and chemical fertilizers, animal manure as well as their combination were also not significant. Further research is recommended to find suitable solutions to the need of the area.