Journal of Soil Management and Sustainable Production
Year:2021 | Volume:10 | Issue:4|Papers Count:9

Soil organic carbon is one of the most important basis for assessing soil quality, health, and fertility. Therefore, accurate, rapid, and inexpensive measurement of soil organic carbon is essential to determine efficient management and conservation practices, which might increase carbon sequestration or preservation in soils. Soil carbon measurement methods are generally classified into two categories: ex-situ and new in situ methods. The first category includes traditional field-collected samples and chemical laboratory degradation of soil organic matter using wet and dry combustion methods. These methods are often expensive, time-consuming, and environmentally destructive. In many cases, common sampling and laboratory errors have resulted in these approaches to be less precise. In situ methods, including infrared reflectance spectroscopy, laser-induced breakdown spectroscopy, inelastic neutron scattering, and remote sensing, are considered more efficient, especially in large-scale national studies as utilizing such methods may increase the speed and accuracy of measuring and significantly reduce the cost of conventional field sampling and laboratory analysis. National quality monitoring of Iranian agricultural soils showed that in more than 60% of lands, soil organic carbon content is less than one percent and further studies have confirmed the declining trend of organic carbon storages in most parts of the country. On one hand, more than 80% of Iran's land area is located in an arid and semi-arid climate whose soils are low in organic carbon content, and on the other hand, the salinity and predominance of calcareous soils in vast areas of Iran have become controversial issues, which have made the attempts to find the correct method of measuring the organic carbon of these soils more complicated. Although the use of an automated carbon analyzer is considered as the standard method for comparing the ex-situ soil carbon measurements, the incomplete conversion of carbonate to CO2 under the combustion conditions in highly calcareous soils might happens which is problematic. Therefore, the use of wet combustion methods is more popular because it’ s not affected by the presence of carbonates and the direct calculation of organic carbon. All soil organic carbon measurement methods have strengths and weaknesses, so its choice depends on the characteristics of the studied soils, the purpose of the project as well as the financial considerations, and the allocated budget. Considering the lack of comprehensive studies in this field, the present study aims to help to gain a better understanding of the results of the Walkley Black method, as the basic method of measuring soil organic carbon in Iran, and to assist with developing a standard and robust protocol for measuring the organic carbon of saline and calcareous soils of Iran, and finally to comparatively evaluate the soil carbon measurement methods by outlining their strengths and weaknesses.

Background and Objectives: Solid waste (SW) of olive oil industries contain valuable organic and inorganic materials which can be useful for soil quality and its microbial activity. However, these wastes contain fatty acids and recalcitrant materials which require special microorganisms for complete decomposition in soil environment. The aim of this study was to investigate soil biological and ecophysiological indicators (as soil quality indices) after addition of oil refinery plant solid waste and inoculation of Bacillus and Pseudomonas bacteria to soil. Materials and Methods: The experiment was conducted in a completely randomized design with factorial arrangement and three replications. Factors included SW (0, 2 and 4%), inoculated bacteria (no bacteria, native Bacillus sp. native Pseudomonas sp., Bacillus persicus and Pseudomonas fluorescens), and sampling time (0, 1, 2, 3, 4, 5 and 6 months). Soil without SW and uninoculated with bacteria was regarded as control. Soil-SW mixtures incubated at laboratory condition (~25 º C) for 6 months. During incubation period moisture content of mixtures was kept constant around 0. 7 FC. Sampling was carried out before incubation start and then monthly throughout incubation period. Organic carbon (OC), basal respiration (BR), substrate induced respiration (SIR), and microbial bimass carbon (MBC) were measured in the samples and ecophysiological parameters including metabolic quotient (qCO2), microbial carbon ratio (Cmic), and available carbon index (CAI) were calculated. Data analysis and mean comparisons were done by Tukey method (P<0. 05) using SAS software package. Results: The effect of all factors and their interactions were significant (P<0. 05) on the studied parameters exept qCO2. The highest values of BR and SIR were obtained in the 4% SW treatment inoculated with Pseudomonads. Adding SW to the soil and inoculating it with Pseudomonads had an important role in the increase of these two parameters value. However, despite the positive role of SW, bacterial inoculation did not increase MBC, while the highest amount of MBC was observed in the 4% SW treatment uninoculated with bacteria. The lowest amount of all three parameters was observed in the 0% SW treatment inoculated with Bacillus persicus. SW addition to soil increased qCO2, and its higher values were observed in the mixtures inoculated with native Pseudomonas sp. SW application and bacteria inoculation to soil decreased Cmic. The highest and lowest Cmic values were observed in soil without SW inoculated with Pseudomonas fluorescens and soil contained 4% SW inoculated with Bacillus persicus, respectively. The mean Cmic values in 0, 2, and 4% SW-mixtures were 10. 32, 5. 06, and 4. 76 mg Cmic gCorg-1, respectively. The trend of Cmic changes over time showed that this parameter had ascending trend in uninoculated soil and soil inoculated with Bacillus bacteria. SW addition to soil and soil inoculation with Pseudomonads increased CAI. The highest and lowest CAI values were observed in 4% SW-mixtures inoculated with Pseudomonas fluorescens and soil inoculated with native Bacillus sp., respectively. The trend of CAI changes was greatly fluctuated over time and its slope was only positive in Bacillus inoculated soils. Conclusion: Overall, the addition of oil refinery plant solid waste to the soil and its inoculation with Pseudomonads, although reduced microbial carbon ratio, increased microbial basal respiration and available carbon index. Therefore, it seems that in the application of this waste in soil, inoculation with Pseudomonas bacteria can accelerate its decomposition in the short term and release its mineral nutrients.

Background and Objectives: About 98% of the soil's potassium is in the form of minerals that are not available to plants. On the other hand, the continues use of fertilizers has unintended consequences for different habitats. Acid producing microorganisms can transform silicate minerals that contain potassium and release available potassium for plants. The aim of this study was to isolate and identify potassium, phosphorus and iron solubilizing bacteria from the minerals of these elements (potassium silicate, tricalcium phosphate, and hematite) from the soil around potato roots in order to make biofertilizers from plant growth-promoting bacteria. Materials and Methods: Potassium solubilizing bacteria were isolated from the soil around potato roots. The isolates were tested and selected in terms of their ability to release potassium from three minerals (biotite, muscovite, and feldspar potassium) qualitatively by spot cultivation based on the emergence of the halo (Halo method) or changing the color of Aleksandrov medium. Then, to estimate the ability of the isolates for releasing potassium, they were cultured in Aleksandrov liquid medium. To investigate the ability for solubilizing t minerals, ricalcium phosphate the isolates were cultured in the same way as described above, but in the Pikovskaya medium. To investigate the ability for solubilizing iron, the modified Pikovskaya medium with hematite mineral was used. This study was performed by a completely randomized factorial design, in which, the minerals used in three levels (muscovite, biotite and feldspar potassium) were the first factor and 30 bacterial isolates were the second factor to release potassium. To analyze the release of phosphorus and iron, a completely randomized design was used and only the ability of 30 isolates for solubilizing of one mineral (tricalcium phosphate or hematite) was tested separately. Statistical analysis was performed with SAS software. Isolates were examined and identified using morphological, biochemical and molecular tests. Then, 10 superior isolates were identified and the plant growth promoting ability tests were performed on them. Results: Among 30 isolates, 10 top isolates were separated and identified for potassium, phosphorus and iron releasing ability. Flame photometric studies showed that the amount of potassium released by the isolates in the medium containing biotite was 647. 18 mg/kg from control to 5416. 16 mg/kg from number 10, in the medium containing muscovite was 148. 68 mg/kg from number 21 to 2026. 36 mg/kg from number 10, and in the medium containing potassium feldspar was 132. 76 from number 7 to 534. 88 mg/kg from number 19. The amount of phosphorus released by the isolates was 3582. 85 mg/kg from control to 37011. 42 mg/kg from number 25 and the amount of iron was 830. 00 mg/kg from number 33 to 2661. 66 mg/kg from number 4. In this study the released potassium from biotite and feldspar minerals by bacterial isolates was the highest and the lowest one, respectively. There was a high correlation between bacterial acid production and solubilizing minerals ability.Conclusion: 10 top isolates were separated and identified from the soil around potato roots based on evaluating potassium, phosphorus and iron releasing ability. In addition to being potent for releasing potassium, these isolates were also capable of producing auxin and siderophores, and also inhibiting pathogenic fungi (which are characteristics of PGPR bacteria). It is suggested to utilize these isolated bacteria in the production of biofertilizers to increase the bioavailability of potassium, phosphorus and iron for plants and to improve the growth and productivity of crops, especially potatoes.

Background and Objectives: Organic carbon plays a vital role in climate control and environmental sustainability by retaining a significant portion of its mineralizable organic forms in the soil. Organic carbon also has a key effect on physicochemical and biological properties of soil; in a way, it is called as an indicator of soil health. Therefore, the study of spatial distribution of soil organic carbon to identify areas with carbon sequestration potential is one of the requirements of soil management planning and climate control policy through agricultural activities. Conventional methods for estimating soil organic carbon are costly and time consuming and cannot be replicated and generalized to similar points. In recent years, with the advancement of technology and the growing human need for access to accessible information and cost savings, through data mining and with the help of satellite images and auxiliary topographic variables, digitization of soil properties, including Organic carbon is made possible. Digital soil mapping is the development of a numerical or statistical model of the relationship between environmental variables and soil properties that is used for large geographic data to produce a digital map. The three main goals of digital soil mapping are: 1) inferring the relationship between environmental variables and soil properties, 2) producing and presenting data that better illustrate soil-geolocation, and 3) explicitly applying expert knowledge in design. They are models. Digital mapping also provides potential advances in soil pedology and geography by providing insights into landfilling processes. Materials and Methods: This study was conducted in Kamyaran city of Kurdistan province in order to predict soil organic carbon. In this study, 110 soil samples were randomly analyzed from different land uses. To better predict the spatial distribution of soil organic carbon in the study area, 101 auxiliary variables extracted from digital elevation model, satellite images and climatic variables have been used. Prediction of soil organic carbon was modeled with two models of multivariate linear regression and artificial neural network in Jump software environment. Results: The results showed that the amount of soil organic carbon in the western and northwestern parts of the study area is the highest, which includes areas with forest and rangeland cover. Auxiliary variables: base level of canal network (40%), band 4 (23%), leaf water content (20%), ground roughness (19%), vertical distance to canal network (18%), slope (18%), Normalized vegetation differentiation index (17%), area level (16%), slope direction (16%), height (16%), band 3 (15%), reflective absorption index (14%), band 1 (14 %), Rain (13%), band 5 (13%), air temperature (12%), vegetation index (11%), topographic wetness index (10%) and vegetation difference index (10%) had the greatest effect On the modeling of soil organic carbon in the artificial neural network model. The results of modeling validation showed that the artificial neural network performed better (R2 = 0. 97) than the multivariate linear regression (R2 = 0. 59) prediction of soil organic carbon in the study area. Conclusion: The results of this study showed that the distribution of organic carbon is more influenced by topographic and climatic factors. In areas where sampling is not possible in the whole area for any reason, it can be used through auxiliary variables such as topographic, climatic and vegetation parameters and with modern data mining methods to estimate soil organic carbon.

Background and Objectives: Soil contamination with heavy metals (HMs) has caused great concern with the development of industry and the rapid increase in human activities. Lead (Pb2+) accumulates easily in the environment due to its non-degradable nature and poses a serious threat to the lives of plants, animals, and especially humans. More dangerously, HMs are usually present simultaneously with different compounds and concentrations, complicating the management of these pollutants. Reducing the bioavailability of HMs by adding stabilizing agents to the soil is a reliable and low-cost way to control HMs pollution. Materials and Methods: in this study, Walnut leaves biochars were produced at three pyrolysis temperatures of 200, 400 and 600 ° C (B200, B400, and B600). For this purpose, 3 g (1% w/w) of the above treatments were added to 300 g of soil sample put in plastic jars, and incubated for 90 days at 21 ± ° C and a humidity of 80% of the field capacity. Then, the soil was sampled at 30 and 90 days after incubation. To measure the adsorption of Pb2+ in the soil, first 2 g of each treated soil into 50 ml centrifuge tubes and 20 ml of PbNO3 solution containing concentrations of 0. 5, 1, 2, 3, 4, 6, 7 and 8 ml of Pb2+ (single system) and Pb2+ + Zn2+ (mole ratio Pb2+ / Zn2+ = 1; competitive system) were added to the tubes in the 10 mM CaCl2 as the background electrolyte. The linear form of the Longmuir equation was used to determine the individual and competitive adsorption characteristics of Pb2+. To determine the desorption of adsorbed Pb2+, 20 ml of 10 mM CaCl2 was added to the residual soils in centrifuge tubes from the adsorption study. Results: The results showed that maximum adsorption capacity (qm) of Pb2+ increased with increasing pyrolysis temperature, so the B600 treatment had the highest maximum adsorption capacity among the treatments. The value of this coefficient decreased in the presence of Zn2+ (P <0. 05). The qm of Pb2+ adsorption in biochar treatments decreased significantly after 90 days of incubation. The highest amount of Pb2+ strength of adsorption (KL) was in the biochar prepared at 600 ° C treatment. The value of this coefficient in the competitive system decreased compared to the individual system. After 90 days of incubation in both adsorption systems, KL decreased compared to 30 days of incubation (P<0. 05). The concentration of Pb2+ desorption in 10 mM CaCl2 solution (less than 1% of adsorbed Pb2+) showed that the exchange mechanism of Pb2+ adsorption by biochars doesn’ t play importance role and probably the main mechanism of Pb2+ adsorption is formation Pb-phosphate. Overall, the results of this study showed that the application of 1% biochar prepared at 600 ° C can affect the Pb2+ adsorption properties in clay calcareous soils in individual and competitive systems. Conclusions: Walnut leaves biochars produced at different temperatures changed the Pb2+ adsorption and desorption process in loamy clay soil in the presence of Zn2+ and the incubation time. Although calcareous clay soils have a high capacity to Pb2+ adsorption, but biochar was able to significantly increase the strength of adsorption and Pb2+ maximum buffering capacity (MBC) in the soil and reduce the desorption of this metal. Therefore, the use of the biochar can be considered as a low-cost and effective adsorbent for stabilizing and reducing Pb2+ mobility in the soil and increasing the productivity and health of agricultural soils.

Background and Objectives: Nowadays, due to limited water resources, the use of unconventional water sources such as wastewater has been given special attention in the world. The presence of some heavy metals in wastewater particularly in the industrial wastewater limits its application. This study was carried out in order to investigate the efficiency of some organic and nano oxide adsorbents in the removal of zinc (Zn) and cadmium (Cd) from industrial wastewater. Materials and Methods: The study was done at four steps including studying the effects of 1) adsorbent mass, 2) exposure time, 3) concentration of heavy metals, and 4) pH on the removal of Zn and Cd from wastewater. At first, an artificial wastewater was created based on 40 mg l-1 Zn and 25 mg l-1 Cd. Four adsorbents including wheat straw and palm fiber as organic adsorbents and titanium nano oxide and iron nano oxide as nano adsorbents each at five doses (0. 2, 0. 5, 1, 1. 5 and 2 g l-1) were applied. Different time durations were implemented in order to assess time effect in addition to the equilibrium time. In addition, the influence of pH at different levels of 3 to 6 on the efficiency of adsorbents was examined. Moreover, in order to study the effect of different concentrations of Zn and Cd on the efficiency of adsorbents, three levels of pollution concentrations were generated by the combinations of 40, 80 and 120 mg l-1 Zn and 25, 50 and 75 mg l-1 Cd. Results: The result showed that the adsorption of heavy metals increased with increasing the dose of each adsorbent in the wastewater. As the application rate of palm fiber, wheat straw, titanium nano oxide and iron nano oxide increased from 0. 2 to 2 g l-1, the adsorption of Zn increased by 49. 4%, 17. 1%, 13. 1% and 11. 4 %, and the adsorption of Cd increased by 41. 1%, 3. 8%, 18. 0% and 1. 5%, respectively. Overall, palm fiber with the optimal level of 1. 5 g l-1 exhibited the best efficiency in the removal of Zn (87. 2%) and Cd (46. 2%). The equilibrium time for the adsorption of both Zn and Cd using wheat straw, palm fiber, titanium nano oxide and iron nano oxide was 300, 120, 30 and 30 minutes, respectively. In fact, the nano adsorbents reached the equilibrium conditions faster than the organic adsorbents. The applied organic adsorbents at pH 6 and the nano oxide adsorbents at pH 4 had the highest efficiency in Zn adsorption. In the case of Cd adsorption, wheat straw at pH 5, date fibers at pH values of 6 and 3, iron nano oxide at pH values of 4 and 5, and titanium nano oxide at pH values of 4 and 3 showed the highest efficiency. The organic adsorbents at lower and the nano adsorbents at higher concentrations of pollution found to be more effective in removing the heavy metals from the wastewater. Conclusion: The findings of this study revealed that during the removal process of Zn and Cd from wastewater, the organic adsorbents had higher adsorption, whereas the nano adsorbents reached the equilibrium conditions sooner.

Background and Objectives: Soil bulk density (BD) is important because of its direct effect on soil properties such as porosity, soil moisture availability, and hydraulic conductivity and its indirect effects on root growth and crop yield. Environmental processes and agronomic practices induce soil bulk density to vary greatly in both space and time. On the other hand, measuring it on a large scale requires a lot of time and is not economical. As a result, indirect methods are used to measure the bulk density when performing large-scale field activities. Pedotransfer Functions (PTFs) have been broadly implemented as indirect cost-effective and time-saving methods in predicting soil bulk density. The purpose of this study is to evaluate the existing Pedotransfer functions in order to determine the bulk density for different soils of Sistan region as well as calibration and provide new Pedotransfer functions for the study area. Materials and Methods: After reviewing different reference, 64 different Pedotransfer functions (PTFs) published in different sources were selected to estimate the bulk density. These Pedotransfer functions were selected in such a way that 1)in a wide range of time scale (from 1957 up to date), 2) from wide regional, 3) from various soil land uses 4) from all types of regression techniques and 5) only using common and easily measured predictors such as sand, silt, clay and organic carbon. The soil samples collected in this study was 220 data, which was obtained from 110 points at two depths of 0-15 and 15-30. Three indicators of absolute mean error (ME), root mean square error (RMSE) and standard deviation of the predicted error (SDPE) were used to evaluate. Results: Among the existing Pedotransfer functions, Benites et al. (2007) with ME value equal to-0. 0008, RMSE value equal to 0. 1038 and SDPE equal to 0. 1033 had the best results. Based on the RMSE value of Yang et al. (2007) with a value of 0. 1038 with a rank of 1 and based on SDPE function with a value between 0. 0976 Leonaviciute (2000) had the best results. For the study area, 5 presented relationships including linear relationship between BD and OC, linear relationship between OC and BD squares, exponential relationship between BD and OC, linear relationship between BD and OC logarithm and polynomial relationship between OC and BD were presented. Conclusion: Based on the results it can be concluded that soil organic carbon (OC) is the most important factor in predicting soil bulk density and using soil organic carbon alone, soil bulk density can be predicted with relative accuracy. It can also be concluded that the 5 relationships developed in this study can be used to obtain the apparent density in the study area.

Background and Objectives: Irrigation management and use of partial root irrigation under saline conditions is one of the sustainable production strategies in agriculture. The production of reactive oxygen species and the cytoplasmic accumulation of smolites is one of the most common plant reactions to salinity stress and dehydration under these conditions. However, few studies have been performed on the variation of enzymes and cellular osmotic regulators in similar salinity and water stresses under the same osmotic and matric potential levels on the two sides of the root and its differences with separate stress conditions. The aim of this study was investigated the effect of partial irrigation management on activity of peroxidase and catalase enzymes, proline content variation under different levels of similar osmotic and matric potentials, in leaves and roots of maize in Fajr cultivar (KSC 260), in greenhouse conditions. Materials and Methods: A factorial experiment with two factors; stress type (salinity, drought and mix stress) and potential levels in three values (-112,-191, and-363 KPa) was performed on the basis of completely randomized design with 3 replications. The culture media was subdivided into two equal sections by nylon for uniform and same distribution of the root in the mixed treatments. At mixed stress, half of the roots were subjected to salinity stress and the other half to drought stress (at corresponding levels equal to the osmotic and matrix potentials). Handmade tensiometers were used for drainage in salinity treatments. Catalase, peroxidase, total protein and proline were measured in both shoots and roots. Also, total dry weight and root of corn plant were calculated. Results: The results showed that with decreasing the potential level, the activity of root peroxidase and catalase had a similar trend (increase) only in individual drought treatments and the drought part of the mixed treatment. In the drought part of the mixed treatment compared to the individual drought treatment, with decreasing the potential level, the activity of root peroxidase increased by 18. 5% and the activity of root catalase decreased by 6. 28%. At the potential level of-363 bar, the dry weight of roots in drought treatment, compared to salinity and mixed treatment increased by 48. 3% and 31%, respectively. Despite different changes in the amount of traits measured in salinity, drought and mixed stresses, at the same potential, no significant difference in total dry weight was observed. Conclusion: Maize plant under the same osmotic and matric potential levels exhibits different physiological and morphological behaviors. The use of partial root irrigation system with saline water in mix treatment will cause less stress than salinity treatment at low levels of osmotic potential to the plant. It seems, modification of plant biochemical reactions is one of the successes of root irrigation method with saline water. Therefore, due to the scarcity of freshwater resources, partial root irrigation with saline water is recommended as a nearly desirable system compared to other full root irrigation systems.

Background and Objectives: Interrill erosion is one of the most important forms of soil erosion in agricultural lands resulting in soil quality decline and nutrients loss. Despite many studies have been done on interrill erosion, few studies have been conducted on the losses of soil, organic carbon (OC) and nutrients due to wind-driven interrill erosion. Therefore, the purpose of this study is to investigate the effects of different percentages of wheat straw coverage and wind velocities on the losses of soil, OC, phosphorus (P) and potassium (K) following to wind-driven interrill erosion on two contrasting cropland soil samples. Materials and Methods: The experiment was conducted as factorial in a completely randomized design using three factors. Two soil samples with maximum aggregate sizes of 2 and 4. 75 mm covered with four levels of wheat straw mulch including 0 (as control), 30, 60, 90% (equal to 800, 1650, and 3300 kg ha-1) were examined at different wind velocities (0, 6 and 12 m s-1), each at three replicates under simulated rain and winds. Therefore, a constant rainfall intensity of 40 mm h-1 was generated for 40 minutes and the amounts of soil loss, as well as OC, P and K losses were measured. Finally, the relationship of wind-driven interrill erosion rate with the OC, P, and K losses was evaluated. Results: The results showed that the loss of soil, OC, P, and K in the studied soils ranged from 8. 1 to 134. 9, 0. 02 to 1. 28, 0. 03×10-3 to 1. 45×10-3, and 0. 007 to 0. 160 mg m-2 s-1, respectively. With increasing the percentage of mulch, the losses were reduced significantly as nonlinear trends. In contrast, higher wind velocities increased the losses of soil and the nutrients. In the absence of wind and coverage, fewer interrill soil losses were found in the soil containing coarser aggregates. The OC loss in the soils was higher than the P and K losses. However, the relationship of soil loss with OC and P losses was closer than that with the K loss. Conclusion: The findings of this study showed that blowing of erosive winds during a rainfall can intensify the losses of soil and nutrients. However, wind velocity enhances the flow stream power, the mulch coverage can reduce the losses by increasing the surface roughness and conserving the soil surface from the direct impact of raindrops. Moreover, the presence of larger aggregates at the soil surface has an effective influence on the interrill erosion control. Based on the findings of this study, 60% was determined as the optimal coverage of wheat straw to control soil loss due to interrill erosion. Therefore, keeping this amount of plant residue coverage on agricultural soils can considerably constrain the losses of soil and nutrients due to wind-driven interrill erosion.