نشریه مدیریت خاک و تولید پایدار
سال نهم شماره 4 (پیاپی 30، زمستان 1398)

Soil quality plays an important role in the link between high production and sustainability of land resources and can affect the quality of air, water and environment. Assessing the impact of management practices under agricultural land uses on soil quality is one of the necessary processes to achieve sustainable soil management in agricultural ecosystems. Therefore, this research was carried out with the aim of investigating the effects of conventional agricultural management systems on soil quality in Zanjan province.

154 soil samples were collected from 77 farms in Zanjan province (27 sites in irrigated and 50 sites in rainfed) at 0-30 and 30-60 cm depths. Considering the main threats which are associated with soil in Zanjan province, 30 soil physical, chemical and biological properties were measured and evaluated as the soil quality indicators. Additive soil quality index was determined by integrating soil quality indicators. Statistical parameters were applied to compare conventional management approaches in irrigated and rain-fed land uses on soil quality.

Under rainfed land use, at 0-30 cm depth, the aggregate stability and saturated hydraulic conductivity were decreased 49.49% and 22.04% respectively compared to the irrigated land use. Soil bulk density in irrigated land use was 3.68% lower than rainfed land use. Organic carbon, microbial biomass carbon, soil respiration and carbon and nitrogen stock index were higher under irrigated than rainfed land use. Under rainfed land use, soil organic carbon was decreased 33.87% and 31.43%, at 0-30 cm and 30-60 cm depth respectively, compared to the irrigated land use. The electrical conductivity at 0-30 cm depth was 50.46% lower than irrigated land use. Under rainfed land use, available zinc was decreased 66.54% and 63.43%, at 0-30 cm and 30-60 cm depth respectively, compared to the irrigated land use. The metabolic quotient in rainfed land use was higher than the irrigated land use and was identified as an indicator of soil degradation in this study. The metabolic quotient was reduced in irrigated land use by 40% and 33.33% at 0-30 and 30-60 cm depth respectively, compared to the rainfed land use. A significant positive correlation was found between organic carbon and soil physical properties including aggregate stability and saturated hydraulic conductivity and soil biological properties including microbial biomass carbon and soil respiration. The additive soil quality index at 0-30 cm depth, was significantly higher in irrigated land use (0.64) than rainfed land use (0.55).

The results showed that in terms of soil productivity and quality, irrigated management has better conditions than rainfed management. However, higher soil electrical conductivity in irrigated land use indicates the necessity of better chemical fertilizer management and assessing water quality used for irrigating lands in Zanjan province. Soil organic carbon was identified as the most important indicator that influenced the quality of studied soils. Using efficient management approaches including conservational tillage, operating appropriate crop rotation and application of equivalent chemical and organic fertilizers which result in increasing soil organic material are essential for both land uses, particularly under rainfed farming.

Low nitrogen use efficiency (NUE) is a global problem in crop production, and agriculture of Iran is not exempt in this regard. Nitrogen (N) fertilizers as a source of nitrogen can be very effective in water, soil and air environmental pollution. Nitrification is a key process in agricultural ecosystems since it results in changes of ammonium to nitrate and eventually loss of considerable amounts of soil nitrogen through leaching and denitrification. The application of nitrification inhibitors (NI) together with nitrogen fertilizers is a strategy to reduce N losses. Thus, the objective of this study were to evaluate the effect of inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) on nitrification rates and nitrification inhibition percentage in some soils of Iran containing representing differences in organic matter content and texture.

An incubation experiment was conducted to evaluate the effect of DMPP on nitrate and ammonium concentration changes in different times and abundance of ammonium (AOB) and nitrite (NOB) oxidizer bacteria in five soils with different texture and organic carbon (O.C). The treatments of experiment included NI at three levels (without N and NI, 200 mg/kg N as ammonium sulfate without NI, and 200 mg/kg N as ammonium sulfate containing 0.8 % NI), five soil types (sandy loam 1 with 0.58% O.C, sandy loam 2 with 0.3% O.C, loam with 0.73% O.C, clay loam with 0.87% O.C, clay with 1.47% O.C), and five sampling times (0, 14, 28, 42, and 56 day).

The results showed that application of N containing DMPP compared to N without DMPP in all soils had significant effect (P<0.001) on reducing nitrification, which was reduced 44.7% on average. DMPP efficiency on nitrification inhibition in experimented soils had significant difference, indicating that nitrification occurs rapidly in soils containing more clay and O.C compared to soils with more sand and low O.C. Nitrification inhibition percentage after 56 day incubation in SL1, SL2, and L were 57%, 46%, and 12%, but in two other soils were about zero. Also there were a positive significant correlation between abundance of AOB and NOB with nitrate concentration (r = 0.6), O.C content (r = 0.9), and total soil N (r = 0.9).

soil nitrification rate are different under influence of factors like soil textural properties and soil O.C content, and DMPP efficiency had inverse relationship with some soil properties including clay%, O.C content, and nitrifier bacterial population. Further these properties can be used in predicting the short term effects of inhibitors.

Soils play an important role in environmental issues and sustainable management and development programs. Then there is a growing need for the preparation of soil maps with high reliability and accuracy. Taking into account the decreasing the chance of conducting new soil surveys due to the limitation of resources, legacy soil data have been receiving a great deal of attention. These data, which carry important information about the state and properties of soil over time and place, can create a perspective for better management of different resources. Considering these issues and also the dependence of better soil management on this legacy information and the importance of using it in environmental management, serious efforts should be made to maintain and reuse these legacy soil data. Then performing some preprocesses in order to maintain and renew this information is obviously necessary, in which rescue and renewal of soil legacy inventories are the most important ones. These preprocess have to be performed before any reusing of them. In spite of global efforts in this regard, no important effort has been made to renew this valuable information so far. However, it has a good history of soil science and is full of legacy soil information inherited from pioneer soil scientists. Therefore, this study aims at rescue, renewal and evaluate available legacy soil surveys as prerequisite processes for reusing them in the framework of digital mapping.

The 10480 km2 study area is located in the border of Isfahan and Chaharmahal-va-Bakhtiari provinces. Due to the existence of Zayandehrud river in this region, it has been surveyed a lot so far. However, because of the lack of access to all these studies, three legacy soil studies covering the whole study area were selected and examined. After recording of the information of these studies in computer and georeferencing the maps, the boundaries of soil map units were digitized. The quality of the maps was afterward evaluated according to the Cornell adequacy criteria. The spatial accuracy of soil map units was then checked and their probable dislocation was finally corrected using available axillary maps and information. Also, the weighted Tau index and overall accuracy were calculated to quantitatively evaluate the quality of the maps.

The information of selected legacy soil maps and profile was successfully recorded in computer in order to keep them from destruction, and a table filled with the information of their soil profiles. The results indicate that the georeferencing of soil maps was done with relatively good quality. The results of quality and efficiency of soil map units’ assessment showed that the map scale is larger than the scale provided on the maps, however, the map legends provide enough information to the users of the map. The investigation of the boundary displacement of the map units showed that the maps had a high-level of spatial accuracy. The results of statistical evaluation of soil map units’ accuracy showed that in all studies as well as their total, the weighted overall accuracy and Tau index of the map at all levels of classification is more than 70% and 50%, respectively, which indicates a good accuracy of the maps.

Despite the public belief about the quality of legacy soil maps, the results of this study indicate well that the studied legacy soil maps have a good quality in terms of their general characteristics. It is also proved that the legacy information and maps can be used with a good degree of confidence in the digital mapping process. Thus, the cost of new soil studies can be saved using this legacy information.

Most studies have reported a strong relationship between water erosion and soil organic carbon (SOC) losses, so that carbon displacement caused by water erosion stated as an important factor affecting the concentration of CO2 in the atmosphere. Therefore, understanding water erosion processes effect on SOC within an ecosystem is essential. Since evaluating the impacts of water erosion on SOC stock dynamic in long-term is difficult without modeling tool, studying of SOC dynamic through use of simulation models in combination with measured data is recommended. Considering that rangelands of Iran have taken a large part of the country, modeling the effect of water erosion on SOC dynamics in rangelands can provide appropriate management solutions for related organizations. The SOC modeling has not been conducted under the influence of water erosion, and this study could be basis for the future of SOC modeling. Therefore, the present study aims to: 1) improve the validation of the Century model as the most widely used model in the soil carbon studies, by using the output of three water erosion models of GLEAMS, WEPP, and ANSWERS, and 2) simulating the SOC stock dynamic under the influence of two erosion scenarios in the semi-arid rangelands of Bajgah.

To conduct this research, 60 soil samples were taken by randomized sampling methodfrom a depth of 0-20 cm of soil in the semi-arid rangelands of Bajgah. To determine the soil bulk density, two cylinders were collected beside each soil puddle (120 samples). After determining the volume of vegetation sampling (number of plots); aboveground biomass, litter and belowground biomass were collected in 17 plots then transferred to the laboratory. Parameterization and calibrating the Century model was performed by using 43 years of weather data, site specific data, as well as physiological and ecological parameters of rangeland. Then, the long-term average of water erosion rate simulated by WEPP, GLEAMS and ANSWERS erosion models entered as input in the Century model. Finally, a water erosion model, that its simulated erosion rate improves the validation results of the Century model, was selected then illustrated the effect of two water erosion scenarios on the changes of SOC stock for two periods of grazing management including period of nationalization of rangelands with moderate grazing management.

The simulation results showed that use of the GLEAMS model output made the Century model more accurately predict SOC stock. Therefore, the GLEAMS erosion model output was used for simulate the SOC stock variations under the influence of water erosion. The simulation results of the Century model showed that the SOC stock in the Bajgah rangelands during the II period with moderate grazing management, decreased from 3496 to 3260.93 (g cm-2) and 3496 to 3243.90 (g cm-2) in the no-erosion and erosion scenarios, respectively and there was no significant difference between them (p<0.05). Also during the III period with no grazing management, SOC stock decreased from 3245.30 to 3356.04 (g cm-2) and 3227.37 to 3350.42 (g cm-2) in the no-erosion and erosion scenarios, respectively and there was no significant difference between them (p <0.05). Generally, water erosion decreased the SOC stock in the semi-arid rangelands of Bajgah compared with the non-erosion scenario by 0.52% and 0.16% in the end of periods II and III, respectively. The erosion resulted in a slight reduction in SOC stock in the semi-arid rangelands of Bajgah compared to the non-erosion scenario. Based on the results of this study, it can be state that the role of grazing management than the erosion in the changes and losses of SOC stock was more evident in the semi-arid rangelands of Bajgah.

Today, the use of biochar in the sustainable management of soil fertility, has been drawing the attention of the scientists as a multi-purpose and environmentally friendly strategic idea. There are several scientific reports implying the outstanding positive effect of biochar on soil fertility and plant growth. On the contrary, some inconsistent reports have mentioned negative or no effect of biochar. Therefore, it is necessary to investigate the effect of any biochar on the soil and plant before any widespread use of any kind. In the present study, the effect of three different biochar and their raw materials on potassium availability and corn growth was studied.

The study was carried out as a two-part-experiment, including laboratory and greenhouse parts. In both parts of the study, treatments included the control (soil without any biochar or its feedstock), Municipal Waste Compost (MWC), Biochar of Municipal Waste Compost (BMWC), Sewage Sludge (SS), Biochar of Sewage Sludge (BSS), Cow Manure (CM), and Biochar of Cow Manure (BCW). In each study, application rates of treatments to the soil, were 1% w/w. In the laboratory part, the effects of the treatments on available-K and parameters of Quantity/Intensity (Q/I) ratio of potassium were investigated. Also the effects of the treatments on plant growth, K-concentration and K-content of corn were investigated in the greenhouse part.

The CM and its biochar, highly increased the available-K by highly increasing the potassium-Q/I parameters compared to the control. While the SS and its biochar lightly increased the available-K by lightly increasing the potassium-Q/I parameters. The CMW and its biochar, intermediately increased the available-K by intermediately increasing the potassium-Q/I parameters compared to the control. Treatments could improve could improve the growth, k-concentration and k-content of corn compared to the control, excepting of MWC in the case of the plant growth, and SS and BSS in the case of k-concentration. Totally, the descending order of treatments in terms of increasing K-availability was as the follows: 1-BCM, 2- CM, 3-BMWC, 4-MWC, 5-SS and BSS, 6-control. The descending order of treatments in improving plant growth conditions and increasing dry weight of the plant was as the follows: 1-CM, 2-BSS and SS, 3- BMWC, 4- BCM, 5- Control and MWC.

Considering the superiority of BMWC to MWC, in terms of affecting on K- availability and plant dry weight, BMWC can be preferred to MWC. Considering the superiority of BCM to CM in terms of the effect on K-availability, K- concentration and content of plant compared to the control, meanwhile its decreasing effect on plant growth compared to CM, it seems that some considerations such as salinity and nutritional balance must be carefully considered and managed in the case of BCM application. Despite the similarity of BSS and SS in terms of increasing plant growth, BSS application can be preferred to SS because of the more value of PBCK, and consequently, the more continuously K-supply.

Cadmium is a very mobile element in soil that is absorbed by plant roots and translocation of cadmium from root to shoot deteriorates crop quality. It enters the food chains of humans and animals easily and is a potential threat to human health. The increase of contaminated areas in the country and the existence of farms under cultivation of various forages and the use of these forage products in the animal feed led to this study was carried out with the aim of investigating the effects of arbuscular mycorrhizal fungi and Rhizobium leguminosarum bv. trifolii on the yield of berseem clover (Trifolium alexandrium) under cadmium stress.

A factorial experiment was conducted in the greenhouse of Faculty of Agriculture, University of Zanjan, using a completely randomized design with three replications. In this experiment, the effects of different levels of soil cadmium (0, 5, 10, 25 and 50 mg/kg) and soil inoculation (without inoculation and inoculation with Funneliformis mosseae, Rhizophagus irregularis, Funneliformis mosseae + Rhizobium leguminosarum bv. trifolii, Rhizophagus irregularis + Rhizobium leguminosarum bv. trifolii, Rhizobium leguminosarum bv. trifolii, Funneliformis mosseae + Rhizophagus irregularis and Funneliformis mosseae + Rhizophagus irregularis + Rhizobium leguminosarum bv. trifolii) on growth of berseem clover (Trifolium alexandrium) were assessed.

The results of this study showed a significant effect (1% and 5% probability level) due to soil cadmium levels on dry weights and N, P, K and Cd concentrations of aerial parts and roots of berseem clover. The dry weights and N, P and K concentrations of aerial parts and roots of berseem clover decreased as the levels of soil Cd increased. The highest dry weights of aerial parts and roots, N, P and K concentrations were measured in treatment co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii and without Cadmium. Also, the lowest dry weights of aerial parts and roots and macronutrient concentrations were observed in treatment 100 mg Cd/kg and without inoculation with microorganism. Soil contamination with Cd decreased the dry weight of aerial parts and roots by 66.49 and 71.11%, respectively. the highest Cd concentrations in aerial parts and roots were measured 11.25 and 17.80 mg/kg in treatment 100 mg Cd/kg and without inoculation with microorganism and the lowest Cd concentrations in aerial parts and roots were 0.0012 and 0.0046 mg/kg in treatment co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii and without Cadmium. The results of the mean comparison of data showed that the Cd concentration in the roots was higher than the aerial parts, and in treatment 100 mg Cd/kg without inoculation with microorganism, Cd concentration of roots was 36.8% higher than the Cd concentration in aerial parts.

Based on the results obtained from this study with the increase in Cd levels of soil, the dry weights and N, P and K concentrations of aerial parts and roots of berseem clover decreased. Soil inoculation with mixture of fungi and bacteria reduced the effect of Cd stress on the growth of clover. Also, the separate inoculation with arbuscular mycorrhizal fungi also reduced the concentration of Cd in the aerial parts and roots. According to the results of this study, in contaminated soils can be used co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii to reduce the Cd concentration and increase the yield of plants.

In the past few decades, accumulation of heavy metals in soils has increased as a result of human activities. Microorganisms are one of the important parts of soil, that their activity can be affected by the high levels of heavy metals such as Cadmium (Cd). Soil biological parameters can be used for evaluating the quality of contaminated soils. Biochar as a soil amendment can control bioavailability of heavy metals in contaminated soils and reduce their transfer risk to the food chain. The objective of this study was to evaluate the effect of corn stover biochar and modified- corn stover biochar on cadmium (Cd) availability and microbiological properties of a Cd-contaminated soil.

A soil sample was collected from the surface layer (0-20 cm) and spiked with different concentrations of Cd (Cd(NO3)2). The contaminated soil was placed in periodic wetting-drying (WD) cycles for about five months in room temperature. Then, corn stover biochar (BC) and modified corn stover biochar with FeCl2 (Fe-BC) were prepared at 500°C and mixed with the Cd-contaminated soil at 2% (w/w). The soil samples were incubated for 90 days. At the end of incubation period, Cd availability and some of microbiological properties of soil including soil microbial respiration (BR), substrate induced respiration (SIR), microbial biomass carbon (MBC) and dehydrogenase activity were measured and metabolic quotient (qCO2) were determined. This study was carried out as a factorial experiment based on a randomized complete design with two factors including Cd contamination (0, 15 and 30 mg Cd kg-1 soil) and biochar type (control (CK), corn stover biochar (BC) and modified-corn stover biochar (Fe-BC)) in three replications under labratory condition.

The results indicated that application of corn biochar and modified-corn biochar led to increase of soil pH (0.19 and 0.21 unit respectively), cation exchange capacity (6.7 and 10.9%), organic carbon (157 and 200%) and decrease of concentration of available Cd (21.8-41.5%) in the soil compared to the control. In general, soil Cd contamination led to a significant reduction in the soil microbiological properties. Application of corn stover biochar and modified-corn stover biochar significantly increased microbial respiration (24.7-58.7%), substrate-induced respiration (16.8-42.5%), microbial biomass carbon (24.5-58.6%) and dehydrogenase activity (28.8-108%). The effects of Fe-BC treatment on changes in Cd availability and soil biological properties were greater than BC treatment.

In general, results of this study indicated that FeCl2 modified-corn stover biochar can be suitable organic amendment for Cd stabilization and may improve soil microbial activities in calcareous Cd-contaminated soils.

Soil physical quality plays a major role in soil quality studies and it is considered necessary for sustainable economic production, conservation of the environment and prevention of soil degradation. To determine the soil physical quality indicators and their optimal range, the specific conditions of land use and type of cultivated plant should also be considered. Unlike other land uses in rice paddies, many soil physical, chemical and biological behavior and properties are altered by adding water to the soil and puddling. Hence, it is expected that its limitations will vary with other soils. Therefore, this study was conducted with the aim of reviewing the definition of soil available water index in assessing soil physical quality based on specific conditions of rice plant and land preparation operations.

40 soil samples were selected from rice paddies of Guilan province, and soil physical and chemical properties were measured. In addition to Dexter's S index, the soil available water index for plant (PAW) was calculated in three different ways including 1) by assumption of filed capacity at soil suction of 100 cm as upper limit of soil water availability (PAW100), 2) by assumption of filed capacity at soil suction of 330 cm (PAW330), and 3) Redefining of PAW using soil saturation moisture and soil moisture at a suction of 2000 cm as the upper and lower limits of soil available water indicator for rice, respectively (PAWrice).

The results showed that assuming the moisture content of the field capacity at the soil suctions of 100 and 330 cm, 65 and 55 percent of the soil samples had a good physical quality, respectively. While redefining of the PAW indicator of rice paddies (PAWrice) confirmed a good to great soil physical quality in 57.5% of the studied samples. In the studied samples, the use of PAW100 overestimated the amount of soil available water in all soil texture classes. While the use of the PAW330 concept has led to an overestimation of the soil available water value in medium soil textural classes (i.e. silty loam and silty clay loam). However, as the soil texture becomes clayey, the estimated soil available water using PAW330 was less than actual value. The variation of the average values of Dexter S and PAWrice indicators in different soil texture classes was observed by the same trend and as silty loam > silty clay > silty clay loam > clay loam > clay. It should be noted that despite the redefining of the soil available water indicator in rice paddies, the value of Dexter's S index in its optimal range for studied soils was more than 0.035.

Difference in the range of soil water availability in rice paddy fields and its effect on rice yields confirmed the need to redefine soil available water indicator paddy fields. In addition, despite the redefining the soil available water indicator, the results indicated that the Threshold value of 0.035 for S index is probably suitable to evaluate soil good physical quality based on the soil water availability for plant in rice paddies.

In recent decades, Urmia Lake has been faced with a significant reduction in the water level.With the continuation of these conditions, the lake will be completely dry and an important environmental issue in the region. Human factors such as land use change are one of the most important factors in the formation and intensification of this crisis. On the other hand, for the optimal management of water and soil and sustainable production in the catchment area, it is necessary to know the exact changes in land use and agricultural land development. The main purpose of this research is to investigate the temporal changes of land use in a 26-year period in the Nazlou Chai sub basin, one of the important sub basins of Urmia Lake catchment area. For this purpose, satellite imagery, GIS tools and land-based data were used to detect and analyze the changes.

In this study, Landsat satellite images were used in 1992, 2013 and 2018. The first year, before the beginning of the lake water level reduction, was selected in 1992. Considering that 2013 is the beginning of more serious activities for the restoration of Urmia Lake and the policy of banning agricultural development and land use change in this catchment area, this year was selected as the second year. The third year was also selected in 2018 (5 years after the more serious start of development inhibitory policies) to assess the latest state of the land use. Using the necessary pre-processing and classification with the maximum likelihood (supervised) method, land use maps were obtained in Envi version 5.3.

Investigating land use maps shows that during the 21 years (from 1992 to 2013), rainfed 18049 ha, orchards 3997ha, irrigated agriculture 1559ha, stone 11048ha, and salt 639ha have increased. While, the rangeland has decreased by 38001 ha. Also, changes in land use over the past 5 years (from 2013 to 2018) has been faced with the highest increase in orchards (about 7143ha), then, rainfed (about 5444 ha). By contrast, there is a decrease in rangeland (about 2725ha), stone (about 4902ha) and irrigated land (about 5417 ha).

The results showed that a lot of land use changes in the sub basin have occurred during 26 years. In the last 5 years, despite increasing attention to preventing the development of agricultural lands, while continuing this incremental trend, land use change in orchards has had the highest change in the study area (about 50%). This significant increase in the development of orchards after 2013 indicates the need for revision of water and soil management in the basin and attention to effective factors such as integrated management of water and soil resources in the catchment areas and socio-economic issues.