Gh. Rahimi; F. Karimi
Abstract
Introduction: Salinization of soil has been reported as a problem in many parts of the world. Salinization could occur either as a result of natural processes e.g. high concentrations of salt in parent materials or groundwater and/or anthropogenic actions such as over-irrigation. The salinization probably ...
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Introduction: Salinization of soil has been reported as a problem in many parts of the world. Salinization could occur either as a result of natural processes e.g. high concentrations of salt in parent materials or groundwater and/or anthropogenic actions such as over-irrigation. The salinization probably affects the chemical and physical properties of soil, soil microbiological processes, plant growth, and soil fauna. Both quantity and quality of water, however, are the most important eco-factors needed for earthworm survival and development, and also biodegradation processes. Materials and Methods: In order to investigate the effect of irrigation water salinity on the survival and growth of earthworm Eisenia Fetida, an experiment was conducted in a completely randomized design with three replications under environmental conditions of the laboratory of Soil Sciences Department of Bu-Ali Sina University in Hamedan. The different types of water used in this study were: distilled water and saline water made with NaCl salt with electrical conductivity (EC) of 2, 4, 6, and 8 dS m-1. The experiment was carried out using completely randomized design in plastic containers of size 19 × 13 × 8 cm. Ten earthworms per container used in each exposure regime were introduced into the relevant test salinity by placing them on the surface and allowing them to burrow in. The test containers were covered with perforated lids to limit water loss due to evaporation and kept in 16 hours light, 8 hours dark at 25°C in a climate chamber for 42 days. Sampling was done at 3, 15, 21, 27, 33, 39, and 42 days after earthworms were introduced to the substrates to investigate mortality and weight changes of earthworms. The LC50 (concentration at which 50% of the earthworms are killed) and the EC50 (effect concentration at which a 50% reduction in a measured parameter) values for the salts expressed as conductivity (dS m-1) were calculated on day 27 and 42 by using the Probit Analysis. Results and Discussion: On day 3, no significant effect of salinity on percentages of survival was found. The survival rate of Eisenia fetida was significantly affected in the EC range used during 42 days (Table 2). The irrigation with distilled water (EC0) had the highest survival rate while the irrigation water with EC 8 dS m-1 had the lowest value. During the 39 days of exposure, no significant difference was found in survival rate of earthworms between EC 2, EC 4 and EC 6 dS m-1, but at the end of day 42, the salinity levels with EC 8 dS m-1 had a significant effect on percentage of earthworm survival in which 91.68% mortality occurred. The mean weight change of earthworms exposed to water with EC 2 dS m-1 was not significantly different (p < /em> < 0.01) from those exposed to the distilled water during 39 days, but there was a decrease in earthworm weight on day 42. The calculated LC50 for mortality after 27 and 42 days was 7.5 and 4.31 dS m-1, respectively, and EC50 for growth was 7.94 and 6.82 dS m-1, respectively. Conclusion: Our results showed that increased salinity had harmful effects on the growth and mortality of the earthworms (Eisenia fetida). Salinity can have detrimental effects on earthworms at concentrations considered safe for many plant species. We determined 42 day LC50 for mortality 4.31 dS m-1 (2521 mg lit-1). The EC50 for growth was 6.82 dS dS m-1 (3989 mg lit-1). The weight of earthworms was significantly affected by NaCl and dispersion analysis showed that NaCl concentration had a statistically significant influence on the weight of earthworms. The argument for using NaCl is that it is the predominant salt in most saline environments particularly in wastewaters. Since the salt type is dependent on the source of the contamination, it is, therefore, possible that other salts apart from NaCl could be the main compounds in saline toxicity in a specific area. The results of the current study suggest that the effects of salinity depend on the salt composition. Therefore, it would be important to assess the type of salt ions in soil in risk assessment, as this affects the extent of toxicity to soil organisms.
Habib Abedi Babaheydari; Rohallah Fatahi Nafchi; Davood Namdar
Abstract
Introduction: The existence of 35 to 45 million hectares of desert areas in Iran and many restrictions such as lack of precipitation, have caused many challenges for the development of these areas. On the other hand, improper utilization of existing resources has resulted in desertification as a natural ...
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Introduction: The existence of 35 to 45 million hectares of desert areas in Iran and many restrictions such as lack of precipitation, have caused many challenges for the development of these areas. On the other hand, improper utilization of existing resources has resulted in desertification as a natural phenomenon, which is increasing annually. The activities that have been tracked down desertification decades ago have only managed to control a very small corner (about 9.1 million hectares) of these areas. Desertification is the consequence of two challenges of climate change and freshwater scarcity. In Iran, 43.7 million hectares are desert ecosystems in the wilderness of the country, of which about 20 million hectares of desert ecosystems are affected by wind erosion. Meanwhile, 4.6 million hectares in 183 districts in 82 counties and 18 provinces of the country are considered critical wind erosion centers. In general, natural and human factors are among the main origins of desertification. In arid and semi-arid areas due to lack of precipitation, water is the most important limiting factor for plant deployment. Due to the quantitative and qualitative limitations of water resources, the survival of plants in desert areas, mainly depends on the choosing appropriate irrigation method. The purpose of this study was to compare Water Box method, which is a particular form of irrigation, with surface and drip irrigations for planting hawthorn plant, which is often used for desertification projects in semi-arid areas such as Iran.
Materials and Methods: Experiments were carried out in the research field at Shahrekord University in the coordinate 32.3526° N, 50.8261° E and 2105 meters above sea level. The study area is 7 km far from the Shahrekord synoptic meteorological station. Shahrekord climate is categorized as Dcas climate by Copenhagen division method, which is characterized by moderate cold weather conditions with warm summers. In surface and drip irrigation methods, five irrigation regimes with zero, 25, 50, 75 and 90 percent of water requirements each with three replications were applied. In the Water box method, due to the self-regulation of the system and the no possibility of deficit irrigation, experiments with 15 similar replications were performed. Plant parameters such as stem diameter, height, seedling survival percentage and water content in each treatment were measured by one-month interval and compared to each other at the end of the study.
Results: The results of this study showed that the Water Box system, while significantly reducing the amount of consumed water (92% than drip irrigation) and high survival rate of seedlings (in this research 100%), is a useful method for establishing some hawthorn seedlings for combat and control of the desertification phenomenon. The highest growth was observed in irrigation treatments with 25 percent low irrigation with 60 cm height growth. Also, the lowest growth is due to irrigation with 90 percent low irrigation. In order to compare the mean annual growth rate of treatments, data were analyzed in SPSS software using the Duncan test at a significant level of 5 percent. The highest water use efficiency was related to water Box irrigation with 2.5 cc/l, which was obtained with a relatively large distance from other treatments, while, as mentioned in the previous sections, the water consumption of this treatment 92 percent low irrigation than full drip irrigation. The lowest water use efficiency was related to irrigation with 75% irrigation, which was 0.15 m3 l-1. In total drip irrigation treatment, water use efficiency was estimated to be 0.16 cm/liter, which shows that although the growth of this treatment was in good condition, it has poor results regarding water use efficiency.
Discussion: Due to the resistance of hawthorn to drought, only three of the cultivated seedlings were dried. The percentage of viability in the Water Box method was 100 percent. However, the difference in the percentage of vitality according to Duncan's method was not significant at 5 percent level. The results of seedling survival percentage were consistent with Naseri et al.(2005). They did not observe the significant difference between irrigation treatments in terms of viability. Due to the lack of research on irrigation with the Water box system, it is recommended that other researches be carried out on the use of this system for irrigation of other (productive) species. The location of the installation and tiling of wicks is one of the things that need to be addressed in the future research.
R. Jenabi Haghparast; A. Golchin; E. Kahneh
Abstract
Heavy metals are entered to the environment by mining and by applying sewage sludge and agricultural inputs to soils. These metals have detrimental effects on environment and soil organisms. An experiment was conducted to determine the cadmium affects on earthworms (Eisenia fetida) in a calcareous soil ...
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Heavy metals are entered to the environment by mining and by applying sewage sludge and agricultural inputs to soils. These metals have detrimental effects on environment and soil organisms. An experiment was conducted to determine the cadmium affects on earthworms (Eisenia fetida) in a calcareous soil amended with 0 and 5% organic matter. The concentrations of Cd in soils were 0,10,20,40, 60 and 80 mg kg-1 and growth parameters of the earthworms were measured with 15 day intervals over 75 days. Survival, growth and cocoon production of earthworms were determined. The results showed that addition of organic matter to soils reduced the toxic effects of cadmium to earthworms. In soils contaminated with Cd the weights of the earthworms decreased with increasing the concentrations of this metal and cadmium had the highest negative effects on cocoon production. The highest earthworm’s mortality was recorded in soils contaminated with cadmium.
S. Nezami; S. H Nemati; H. Aroiee; A. Bagheri
Abstract
Although mint species are very sensitive to water deficit stress, but their reaction may be different to reduction of water in soil during growing season. In order to evaluate response of three Mentha species to water deficit stress, an experiment was carried out in a factorial-randomized design with ...
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Although mint species are very sensitive to water deficit stress, but their reaction may be different to reduction of water in soil during growing season. In order to evaluate response of three Mentha species to water deficit stress, an experiment was carried out in a factorial-randomized design with five replication in controlled conditions and Mentha longifolia (wildmint), Mentha spicata (spearmint) and Mentha piperita (peppermint) species were subject to four soil moisture regimes (100, 80, 60, 40 of field capacity (FC)). Plants were on 70% of flowering at the harvest time. Characteristics were included percent of survival, number of total branches and stolon, number of leaf, length of total branches, green area and total dry matter. The results showed that soil moisture treatments had significant effect on survival of three mint species, because spearmint’s survival was 100 in 60 FC, while in wildmint and peppermint were decreased to 70 percent. In peppermint number of total branches and stolon were significantly excel as compare as two other species, however in spearmint number of total leaf, green area and total dry matter were more than two other species, whereas length of total branches in wildmint were higher than spearmint and peppermint. Spearmint had the greatest dry matter in 100 percent of FC and reduction of soil moisture to 80 percent of FC caused 35 percent reduction in previously mentioned parameter, while in wildmint and peppermint 62 and 56 percent reduction were observed, respectively. However spearmint was more tolerant than two other species to water deficit stress, but more study must be achieved for better understanding of mint responses to water deficit stress
