JWSS - Journal of Water and Soil Science

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The moisture content of urban solid wastes in Iran is very high. A large volume of leachate is, therefore, produced in the process of converting these wastes into compost. The leachate contains relatively large amounts of organic matter, plant nutrients, soluble salts as well as small amounts of some heavy metals. The effects of urban solid waste leachate on growth and yield of corn and heavy metals and nutrients concentrations in plant as well as the effects of leachate residual on soil were studied in a field trial conducted in two sites (Zeinal and Lavark) in central Iran (Isfahan). The treatments included applications of 0, 400, and 800 metric tons of leachate/ha as the main plots and two leaching treatments (0 and 15 cm leaching) as the sub-plots in a split plot design. Application of the leachate decreased crust formation and greatly improved germination and growth of corn in both sites. Biological yield of corn increased from 2.4 to 4.1 and 5.3 tons/ha in Zeinal field and from 8.1 to 13.4 and 15.0 tons/ha in Lavark field for 400 and 800 tons/ha of leachate applications (as compared to the control field), respectively. Leaching increased corn yield only in Zeinal field. Uptakes of N, P, K, Fe, Mn, Zn and Cu by corn increased as a result of leachate application. Concentrations of Fe, Mn, Zn, Cu, and Cl in plant tissues also increased but no toxic symptoms were observed in plants. Concentrations of Pb, Cd, Cr, Co, and Ni in aerial tissues of corn did not increase as a result of leachate application. The residual effects of leachate application on soil were a decrease in pH and corresponding increases in organic matter content, in electrical conductivity and in available amounts of N, P, K, Fe, Mn, Zn, and Cu. It is concluded that garbage leachate has the potential to be used as an organic liquid fertilizer and soil amendment to improve soil productivity.

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In this research, the presence of metalaxyl residues was studied in field-grown cucumber. Two different formulations of metalaxyl were used in the experiments. In the first experiment, cucumber plants were sprayed once and repeatedly by Ridomil-MZ 72 WP at 2.5 g/litre. In the second experiment, single and double applications of metalaxyl granule 5G were carried out at 5 g/m². Leaves and fruits were sampled at different times after each treatment and analyzed for metalaxyl residues by HPLC.

In leaf samples from single sprayed plots, metalaxyl residues declined rapidly following the treatment and more than 50% of the residues disappeared in the first two days, whereas in the leaf from single granule-applied plants, the residues increased during the first three weeks and then declined. Metalaxyl residues in cucumber sampled from single sprayed-plots were at a high level during the first three days after the spray and declined below the MRL (0.5 mg/kg) on the 7th day. In granule-applied plots, the residues increased during the first 7 days and the level below the limit was recorded 20 days after application. Residual values for plants sprayed with suspension showed a faster dissipation rate than granulated treatment. Metalaxyl recovered after three times of spraying and two times of granular application did not show any toxic accumulation of residues in fruit.

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Soil organic matter and clay minerals adsorb and immobilize extracellular enzymes of microorganisms and increase soil enzymes stability. This study aims to clarify the relative importance of soil organic matter and clay minerals on the cellulolytic activities of soils. Fluca prepared cellulase was immobilized on some agricultural residues and clay minerals, avicel and a sample of soil. Immobilized exoglucanase and endoglucanase were assayed at different times. Activities of the immobilized enzymes were strikingly dependent on the kind of sorbent. After 20 days of storing in refrigerator at 4^oC, the deactivation of immobilized enzymes on the organic substances (as avicel) was very low but deactivation of immobilized enzymes on the soil and clay minerals was relatively high. On the other hand, the activities of immobilized enzymes on the agricultural residues and avicel were significantly higher than the soil and clay minerals. So it may be concluded that a large part of cellulolytic activity of soil is related to immobilized enzymes on agricultural residues. Coating of the clay minerals, soil and avicel with 4 mmol of Al (OH) x per mg of them significantly increased their immobilization capacity and activities of immobilized enzymes. Activities of immobilized exoglucanase and endoglucanase on the Ca- homoionized soil and clay minerals were significantly higher than the K- homoionized soil and clay minerals. However, these effects may be related to the specific effects of cations on the method of enzyme assay or enzymes activities. These homoionizing-cations effects on the activity of immobilized enzymes on avicel were not significant.

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Vegetable crops are exposed to repeated spraying against the pests and diseases during the growing sessions. Crops such as greenhouse cucumber are usually harvested a short time after spraying, bearing a high level of pesticides with them. This fact justifies a research on this problem. This research was carried out to determine the effects of metalaxyl (a fungicide commonly used in greenhouse) residue in cucumbers grown under traditional and modern greenhouse conditions. Cucumber plants were sprayed with two different doses: 1/1 000 and 2/1000 metalaxyl in modern and traditional greenhouses. Samples were collected 1, 2, 4, 7, 10, 14, 21 and 28 days after spraying with metalaxyl. The fungicide residue was extracted, cleaned up by TLC and the final solution was analyzed by HPLC. Data were analyzed statistically by t-test (paired observations) and Duncans multiple range test. The results revealed that the amount of metalaxyl residues increased in the first four days following spraying. This amount of the residue was 10 times higher than MRL (0.5 mg/kg), while a lower level of MRL (0.5 mg/kg) was detected 21 days after the application. Results also showed that a lower dose of application left a higher residual level than the higher one. On the other hand, no significant differences (p<0.05) were found between the amounts of residues in peeled and unpeeled cucumbers. Thus, fruit peeling does not reduce the fungicide residue in cucumber. Also, there were no significant differences (p<0.05) between the results obtained from modern and traditional greenhouses. Therefore, cucumber must either be harvested before or at least 14 days after spraying with metalaxyl.

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Under irrigation and in double-cropping system, a large amount of plant residue remains after harvest that along with the limited time for residue decomposition and complete seedbed preparation, necessitates reduced tillage and special residue management. In the present study, the effects of various seedbed preparation methods on vegetative growth, yield components and seed and oil yields of sunflower (Euroflor hybrid) were studied in a barley-sunflower cropping system during 2001 at the Agricultural Research Station, Isfahan University of Technology. Three residue management treatments (standing, partly removed and burned) along with five tillage systems (moldboard + disk chisel + disk disk moldboard and furrower as the minimum tillage) were laid out in a split-block design with three replications. Burning residue treatment significantly increased plant dry weight at various developmental stages and also head diameter. Number of seeds per head, 1000 seed weight, harvest index, and oil yield were non-significantly higher in the burned residue treatment. Seed yield was significantly higher in the burned and partly removed residue treatments. Moldboard + disk and chisel + disk treatments significantly produced higher plant dry weight at various developmental stages, head diameter and seed yield. Number of seeds per head, 1000 seed weight, harvest index, and oil yield were non-significantly higher in these treatments. Minimum tillage ranked the lowest for these traits. The results of this experiment indicate that chisel + disk treatment with the partly removed residues might be an appropriate seedbed preparation method in a barley-sunflower double planting under conditions similar to this experiment.

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Regarding the public concerns about serious health risks from pesticide, the occurrences of 105 pesticide residues including Organochlorine, Organophosphorus, Organonitrogen, Dicarboximides, Strobilurin, Triazine, Pyrethroids were assessed using a descriptive method in 25 fresh and greenhouse vegetable samples (fresh carrot, greenhouse tomato and cucumber). Ethyl acetate was used for extraction of pesticides from samples and the extract was cleaned up by Envicarb Solid Phase Extraction column chromatography. Pesticide residues were identified and quantified using gas chromatography ion trap mass spectrometry detector. The mean recoveries and limit of detection of the pesticides in samples were respectively 61.67-117% and the reproducibility of relative standard deviation values for the pesticides was 3.49-14.55%. Our data demonstrated that 80% of the total analyzed samples contained detectable residues including trifluralin, permethrin, chlorpyrifos, fenvalerate, fenpropathrin and iprodione, which were below the accepted maximum residue limits (MRL_S) adopted by FAO/WHO Codex Commision Alimentarius.

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The effects of tillage methods and residual management on yield and yield components of rapeseed (Brassica napus L. CV. Hyola308) were evaluated after rice harvest. The experiment was carried out during 2004-2005 cropping season in a factorical arrangement of treatments at Rice Research Institute of Iran (RRII) in Rasht, in a Complete Randomized Block Design with three replications. Treatments included tillage in three methods: a) conventional tillage b) minimum tillage, and c) no tillage, and rice residue management in two manners: a) removing residues, and b) not removing residues. Plant traits such as grain yield, oil percentage and yield, plant density, plant height, the lowest pody branch height from soil surface, number of pods per plant, plant and weed dry weight, leaf area index (LAI) and crop growth rate (CGR) were measured. Results indicated that grain yield was affected by the tillage type. Also, the effect of tillage type on plant height, number of pods per plant, the lowest pody branch height from soil surface, and oil yield was significant. The effect of residual management and residual management interaction and tillage were significant on none of the traits except for weed dry weight. Economic analysis indicated that rapeseed planting in a field with rice residual and minimum tillage had a relative advantage of less production cost in spite of nearly 15 percent yield decrease compared to other methods.

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Crop residues are beneficial substances that can bring about important changes in soil biological, chemical and physical properties and can also increase or stabilize crops yield. A field experiment was carried out at Research Station of College of Agriculture, Shiraz University, Shiraz, Iran, to determine the effects of wheat (Triticum aestivum L.) residue rates in combination with N levels on some soil properties in common bean (Phaseolus vulgaris L.) cultivation for two years (2008-2009). The experiment was conducted as split split-plot arranged in a completely randomized blocks design with three replications. Treatments were two red bean cultivars as main plots, N levels (0, 34.5, 69, and 103.5 kg ha-1) as sub-plots and residue rates (0, 25, 50 and 75%) as sub sub-plots. The results showed that application of crop residues significantly increased soil organic carbon, N, K, and P contents. Heavy crop residue (75%) application had no effects on these soil properties. Thus, retaining 50% crop residue was optimum for proper soil quality. Increased N application increased soil N, decreased P and K contents, and had no effects on organic carbon.

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Limited information is available about the effect of preceding crop residues on bioavailability of zinc (Zn) in calcareous soil and its accumulation in wheat grain. In this experiment, residues of five crops including safflower (Carthamus tinctorius L.), sunflower (Helianthus annuus L.), bean (Phaseolus vulgaris L.), clover (Trifolium pretense L.) and sorghum (Sorghum bicolor L.) were incorporated into a calcareous Zn-deficient (0.5 mg kg-1) soil. A treatment without crop residue was also used in the experiment. This experiment was conducted in research greenhouse of Isfahan university of technology in 2010. Two wheat cultivars (Triticum aestivum cvs. Backcross and Kavir) differing in Zn-efficiency were studied in the experiment. Incorporating crop residues into the soil resulted in an increase of grain Zn concentration in both wheat cultivars although this increase was dependent on the preceding crop type. The greatest increase of grain Zn concentration occurred in the sorghum residues treatments. Although application of crop residues significantly decreased grain phytic acid to Zn molar ratio (as Zn bioavailability criteria for consumers), this ratio was still higher than 15, the critical Zn bioavailability level for consumers in foods. According to the results, despite the increase in the total Zn content, the bioavailability of Zn in wheat grain was not affected by crop residue treatments.

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The objective of this study was to evaluate the effects of crop residues management on soil physical and biological properties. The impacts of residue management on yield of forage corn and barley and soil micro-organisms population were also studied. The results showed that application of crop residues increased soil organic matter (22.2 %), saturated hydraulic conductivity (51.9 %), porosity (3.7 %), mean weight diameter (MWD) of the aggregates (5.4 %), and field capacity (5.8 %) and decreased bulk density (3.7 %) Whereas crop residues burring decreased soil organic matter (31.8 %), saturated hydraulic conductivity (36.6 %), porosity (0.5 %), mean weight diameter (MWD) of the aggregates (5.1 %), and field capacity (4.1 %) and increased soil bulk density (1 %). Soil water characteristic curves showed that the observed differences in soil water retention of application and burning residues treatments were higher at low matric suctions than those at high water matric suction. The results demonstrated that micro-organisms population significantly (P<0.05) decreased in residues burning treatment compared with the residues application treatment. Therefore, based on the results of this study residues' burning is not recommended in Ardabil.

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Water management in cracked paddy soils is an important issue in rice cultivation. In order to study organic matter and zeolite effect and their interaction on moisture conditions and hydraulic and physical properties of paddy soils, the organic matter (rice straw) at four levels (0, 8, 16 and 24 tons per hectare), zeolite at four levels (0, 0.5, 1 and 1.5 percent ), and also moisture stages of soil at 5 levels were selected. This experiment was conducted in Rice Research Institute of Iran. Randomized Complete Block Design (RCBD) was used to study the effect of treatments on different subjects. The amount of moisture, bulk density and the distance of soil from the wall of container were measured in a 4-month period. The obtained results showed that the interaction effects of organic matter and zeolite on soil moisture content were statistically significant at one percentage level. Addition of plant residues caused an increase in soil moisture weight and reduction in bulk density compared to the control treatment. It was also found that soil moisture content and bulk density were highly correlated. Bulk density of control treatment ranged from 0.75 to1.7 gr/cm3, while with addition of 1.5 % crop residue the bulk density ranged from 0.7 to 1.3gr/cm3. Overall results show that crop residues are effective in reduction of crack parameters of soil , but zeolite cannot be effective although it causes more maintenance of soil moisture.

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