Dynamics of soil organic carbon following land-use change: insights from stable C-isotope analysis in black soil of Northeast China

Intensive soil tillage is a significant factor in soil organic matter decline in cultivated soils. Both cultivation abandonment and foregoing tillage have been encouraged in the past 30 years to reduce greenhouse gas emissions and soil erosion. However, the dynamic processes of soil organic carbon (SOC) in areas of either continuous cultivation or abandonment remain unclear and inconsistent. Our aims were to assess and model the dynamic processes of SOC under continuous tillage and after cultivation abandonment in the black soil of Northeast China. Soil profiles were collected of cultivated or abandoned land with cultivation history of 0–100 years. An isotope mass balance equation was used to calculate the proportion of SOC derived from corn debris (C4) and from natural vegetation (C3) to deduce the dynamic process. Approximately 40% of SOC in the natural surface soil (0–10 cm) was eroded in the first 5 years of cultivation, increasing to about 75% within 40 years, before a slow recovery. C4 above 30 cm soil depth increased by 4.5%–5% or 0.11–0.12 g·kg−1 on average per year under continuous cultivation, while it decreased by approximately 0.34% annually in the surface soil after cultivation abandonment. The increase in the percentage of C4 was fitted to a linear equation with given intercepts in the upper 30 cm of soil in cultivated land. A significant relationship between the change of C4 and time was found only in the surface soil after abandonment of cultivation. These results demonstrate the loss and accumulation of corn-derived SOC in surface black soil of Northeast China under continuous tillage or cultivation abandonment

The Influence of Bean Rhizosphere on Some Chemical and Biological Properties in Soils Amended with Municipal Sewage Sludge

Introduction: The biological and chemical conditions of the rhizosphere are known to considerably differ from those of the bulk soil, as a consequence of a range of processes that are induced either directly by the activity of plant roots or by the activity of rhizosphere microflora (16). Municipal sewage sludge (MSS) applied to agricultural soils is a well known reusable source of phosphorus (P), nitrogen (N) and other macro- and micro-nutrients (33). Sludge provides a short-term input of plant-available nutrients and stimulation of microbial activity, and it contributes to long term maintenance of nutrient and organic matter pools (33). Availability of P following application of MSS can be influenced by microbial and chemical properties of the soil, MSS composition, and rhizosphere processes. The specific interrelationships between these components have proven to be complex and, despite continued study, a thorough understanding of the interactions among plant roots, manure P, and P solubility has yet to be achieved (42). Little quantitative information is available about the chemical and biological properties in the rhizosphere of bean plant growing in soils un-amended and amended with MSS. Therefore, the objectives of this research were to evaluate the rhizospheric effects of bean on chemical and biological properties in 10 calcareous soils as amended with municipal sewage sludge (MSS) or unamended (control) under rhizobox conditions. Materials and Methods: Ten surface soil samples (0–30 cm) were collected from Chaharmahal-Va-Bakhtiari province, in the central Iran. Municipal sewage sludge was used from the refinery of Shahrekord city, central Iran. Air dried and sieved

Evaluation of Some Physiological and Quantitative Traits in Different Ecotypes of Linseed (Linum usitatissimum L.) Under Chemical,Organic, and Biological Nitrogen Fertilizers

Nitrogen is one of the major macronutrients in cropping systems. Considering the effect of nitrogen on the quantitative and qualitative characteristics of linseed, a field experiment was conducted as factorial arrangement in a randomized complete block design with three replications in the Research Station of Faculty of Agriculture, Shahrekord University in 2012. Five fertilizer treatments of urea, Azomin, Nitroxin, Super NitroPlus and control (without fertilizer) and three ecotypes of Iranian, Canadian and French linseed in this experiment were examined. Harvest index, seed protein and oil contents (%) were evaluated. Meanwhile, the trend of the cumulative crop growth rate (CGR) and fitted regression model was studied. Harvest index was significantly different between ecotypes. Harvest index, seed protein and oil contents showed significant responses to fertilizer treatments. The interaction between ecotypes and fertilizer treatments was significant for harvest index and seed oil content. Non-linear regression model (peak) best fitted on the trend of crop growth rate (CGR) in different ecotypes and different fertilizer treatments. According to result, it seems biological fertilizer of Super NitroPlus, Nitroxin and organic fertilizer of Azomin are capable of being hired in sustainable agriculture as an alternative to chemical fertilizers in linseed cultivation

Soil Organic Carbon Dynamics in Native Rangelands Exposed to Grazing and Ungrazing Management in Rangeland Ecosystems of Central Zagrous

The study of soil C dynamics and factors controlling this important soil process in rangeland ecosystems may provide an insight into understanding and evaluating changes in the global C cycle. The primary objective of this study was to quantity the effects of pasture management (i.e., grazing, controlled grazing and ungrazing) on soil C levels and mineralization in three natural rangeland sites of Chaharmahal Va Bakhtiyari province. Three range management regimes including: (a) long-term ungrazed, (b) controlled grazed and (c) free (over) grazed in close vicinity were selected at three sites including SabzKouh (protected from grazing for 18 years), Boroujen (protected from grazing for 23 years) and Sheida (protected from grazing for 2 years). Soil samples were collected from 0-15 cm depth and organic C, total N and C mineralization were measured using standard methods. Results show that SabzKouh and Sheida sites had the highest (14.6 mg g-1) and the lowest (4.80 mg g-1) soil organic C contents, respectively. Soil total N and organic C contents at SabzKouh were significantly higher when compared to other sites, probably due to more rainfall and humid climate. The effect of range management on soil C mineralization was evident at two of the three sites. Results indicate that the exclusion of grazing animals resulted in an increase in soil C mineralization at SabzKouh and Boroujen sites, probably through the addition of plant residues and animal excrements to the soil. However, ungrazed management did not improve plant cover and soil properties in Sheida area, due likely to dry climate conditions, less biomass production and the history of cultivation and agricultural uses. It is, therefore, concluded that the effect of grazing on soil C mineralization depends primarily upon the plant community and climatic conditions and also upon the type of rangeland management and even land use history involved

Evaluation the Efficiency of Six Sunflower Cultivars in Phytoextraction of Lead from a Pb-bearing Soil for Long Term

The right selection of an appropriate cultivar, which can be adapted with a particular pollutant and environmental conditions, is a crucial factor for a successful phytoremediation technology. Sunflower might be a suitable plant to remove the toxic metals from soil of polluted sites due to its rapid growth and high biomass production. In order to evaluate the efficiency of six sunflower cultivars in lead (Pb) phytoextraction from a contaminated soil, an experiment was carried out using a completely randomized design with three replications in Research Station of Shahrekord University. Sunflower cultivars used in this experiment were Alestar, Serena, Sanburu, Hysun 33, Record and Euroflor. Results showed that there was a significant difference in shoot lead concentration, translocation factor and total lead harvested by shoot among sunflower cultivars at 1% probability level. Generally, due to translocation factor of all cultivars was less than 1, this can be stated that none of cultivars had the proper efficiency for extraction of lead from contaminated soil. However, high root lead concentration and low translocation factor of these cultivars show that efficiency of them for use in phytostabilization technique is more than phytoextraction technique

Isolation and Evaluation of Lead (Pb)-Tolerant Plant Growth Promoting Rhizobacteria from a Soil Containing Pb for Long Term

This study was performed in order to isolate lead (Pb)-tolerant plant growth promoting rhizobacteria in Pb-contaminated soils and to evaluate their potential for production of plant promoting substances. The isolated Pb-tolerant rhizobacteria were identified as Rhodococcus sp., Bacillus stearothermophilus strain A, Corynebacterium sp., Bacillus pumilus, Mycobacterium sp., Bacillus stearothermophilus strain B, Bacillus licheniformis and Bacillus sp. The results showed that all isolates were able to tolerate high concentrations of Pb. The minimum inhibitory concentration (MIC) of these bacteria was in the range of 1100-1720 mg l-1 (3.3-5.19 mM). In addition, all isolates produced IAA (ranging from 3.53 to 43.64 mg l-1) and siderophore (ranging from 57.74 to 86.24%). However, only two isolates (i.e., Bacillus licheniformis and Mycobacterium sp.) had the ability to produce bacterial enzyme ACC-deaminase. Inoculation of medium containing poorly soluble PbCO3 with bacterial strain Corynebacterium sp. significantly increased the available concentration of Pb

Effect of Rangeland Fire on Soil Physical Properties and Water Infiltration Parameters using Principle Component Analysis

Annual fires might change many soil physical properties in semi steppe rangeland.The objective of this study was to investigate the impact of fire on soil physical properties and soil water infiltration parameters in semi-steppe rangeland of Karsanak region in Chaharmahal and Bakhtiari province. Therefore, several sites were chosen which were affected by fire at three, two and one years prior to this study (i.e. 2008, 2009 and 2010, respectively). Soil water infiltration was measured using tension infiltrometer in 54 points of the study sites. Since the soil samples were taken from to depth (0-10 cm and 15-25 cm) of each site, the numbers of soil samples for laboratory analysis were 108. Independent t-test and principle component analysis (PCA) was used to assess the difference between the measured properties at the burned and control sites. The results showed that aggregates stability coefficients (MWD and GMD) in the surface layer significantly reduced in 1 and 2 years after fire compared with control areas. Water dispersible clay (WDC) and bulk density significantly increased in surface layer of all burned areas compared with control areas. Saturation hydraulic conductivity significantly decreased in burned areas in 1, 2 and 3 years after. The results showed that annual fires occurs have meny negative effects on soil physical properties cause to shallow, low water retention capacity and high risk of erosion in semi steppe rangeland

Environmental soil contamination by Toxocara species eggs in public places of Ilam, Iran

Introduction. The purpose of the study is to assess environmental contamination by Toxocara species eggs in public places in the city of Ilam, Ilam Province, southwest Iran Materials and method. Between September 2018 and March 2019, 130 soil samples were collected from public places of 5 district municipalities of Ilam, southwest Iran. Soil samples were examined by microscopy following flotation method by sodium nitrate. Results. Soil analysis showed that 5.88% of the soils stored, 52.54% from gardens, 29.42% from rubbish, and 11.72% from green spaces were contaminated with Toxocara spp. eggs. In total, 13.08 % of soil samples (17/130) were positive for Toxocara eggs (P>0.05). Conclusions. The findings revealed that care should be taken when using soil from gardens, green spaces and rubbish, and also should be seriously considered because of the potential issues of toxocariasis and also the risk to the public