JWSS - Journal of Water and Soil Science

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Twenty-two surface soil samples (0-20 cm) from Fars province were extracted by five extractants (i.e., DTPA, 1.5 M NH₄H2PO₄, 0.1 NH₃PO₄, 0.05 MNa2EDTA, and 1% Na₂EDTA) and used in a 7-week greenhouse experiment which was a 22 × 3 factorial with 22 soils (clay 16-63% pH 7.8-8.2 electrical conductivity 0.32-1.78 dS m^-1 calcium carbonate equivalent 28-63% organic matter 1.1-4.9% cation exchange capacity 9-27 cmol kg^-1 and DTPA-extractable Mn 4-24 mgkg^-1), 3 levels of applied Mn (0, 10, 20 mg Mn kg^-1 as manganese sulfate), 3 replications, and soybean [Glycine max (L.) Merr., cv. Williams]. Application of Mn significantly increased top dry weight by 4 to 104%, averaging to about 12% over the control. But the increase in Mn concentration was not significant. Total Mn uptake also significantly increased but the apparent recovery of the applied Mn was very low (i.e., 0.05%). Soil pH, calcium carbonate equivalent, and clay content were found to be the properties influencing the extractability of Mn. The DTPA-extractable Mn, alone (with a critical level of 13 mg Mn kg^-1) or along with some soil properties, was the only form of Mn that could reasonably predict the plant responses.

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Knowledge of forms of phosphorus (P) is important in the evaluation of soil P status and also in understanding soil genesis and fertility. Amounts and distribution of P in different organic and inorganic fractions were examined in 39 soil samples of Fars province. Soils were sequentially extracted to determine organic P and inorganic P fractions. Total P with an average of 597 mg/kg soil was lower in the light soils (482 mg/kg) as compared with the heavy soils (690 mg/kg). Organic P constituted considerable portions of TP (27%). Calcium phosphates with an average of 424 mg/kg soil and being comprised of 71% inorganic P was the dominant form of soil phosphorus. Simple regression analysis indicated that there were significant positive relationships between organic P, Ca phosphates and Al-Fe phosphate values with CEC and clay content. Stepwise multiple regression analysis showed that a combination of soil properties such as clay content and equivalent calcium carbonate (CCE) increased correlation coefficients (R). Alghough multiple regression model was significant (at P<0.05), the relative contribution of each soil property in Al-Fe-P fraction was not considerable.

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Information about forms of zinc (Zn) is important for the evaluation of its status in soil and also understanding of the soil fertility and chemistry. To obtain such information, amounts and distribution of Zn in different fractions of 20 soil samples of Tehran province, Iran were determined by sequential extraction method and their relationships with each other and with soil characteristics were investigated. Total Zn of soils ranged from 70 to 169.9 mg/kg^-1. The amount of different Zn forms relative to the sum of forms was determined to be as follows: organic less than 0.1, soluble+exchangeable 0.1, manganese-oxide-associated 0.9, carbonate 1.6, crystalline iron-oxide-associated 3.8, amorphous iron-oxide-associated 4.2, and residual form 89.3%. Simple correlation coefficients showed that pH had a negative significant correlation with all forms of Zn except organic. Silt and clay contents had significant positive correlations with total, residual, and crystalline iron-oxide-asociated Zn but CEC had significant correlation only with total Zn. Calcium carbonate equivalent showed a significant correlation with soluble+exchangeable, manganese-oxide-associated and amorphous iron-oxide-associated Zn. DTPA-extractable Zn was significantly correlated with soluble+exchangeable, carbonate, and amorphous iron-oxide-associated Zn. A significant correlation was also observed between the Zn forms themselves, which is presumably a reflection of the existence of a dynamic relation between the chemical forms of an element in soil.

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Study of phosphorus reactions over time and the role of organic matter in the calcareous soils are important for the development of P fertilizer and manure management practices. The objective of this study was to determine the effect of applied manure on P availability and its chemical forms in the soil, over time. Eight samples were collected from semi-arid calcareous soils of Mashhad plain. The samples were treated with two levels of inorganic P (0 and 300 mg P kg^-1 soil as KH₂PO₄) and two levels of organic matter (0 and 1% cattle manure). The experiment was conducted in a completely randomized design with factorial arrangement. The treated soil samples were incubated for 2, 5, 10, 30, 60, 90 and 150 days, then analyzed for available P (Olsen-P). The result showed that only 17% of added phosphorus was available in P treatment at the end of experiment. In manure treated soils, this figure reached 34% for the same period of time. Application of manure along with P increased the recovery of applied P and CBD-P (Citrate-Bicarbonate-Dithionite). This may be due to the formation of P-organic complexes with Fe oxides. Application of manure in soil increased NaCl-NaOH-P considerably compared with P and P+OM treatments. It can be concluded that P originating from manure compared with inorganic-P may be more available for plants over the time.

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In order to investigate mineral manganese forms and their relations with plant responses, 22 soil samples from Fars province (0-20 cm) were in a greenhouse experiment filled in 3 liter pots, and soybean (Glycine max (L.) merr.,CV.Williams) was grown for 7 weeks. Chemical forms of manganese were determined in soils by warden and Reisenauer sequential extraction method (readily soluble, weakly adsorbed, carbonate bound and oxide bound extracted with Ca(No₃)₂, Ca DTPA +Na₂B₄O₇, HNO₃ and NH₂OH. HCl, respectively) after harvesting the plants. Results showed that the amount of Mn in different forms was in the following order: Carbonatic Mn >Mn Oxides >Weakly adsorbed Mn > Soluble Mn. Regression equations between soil properties and Mn forms showed a significant correlation between calcium carbonate equivalent and carbonate bound Mn. Significant correlation between Carbonate bound Mn and concentration of Mn in the aerial part of soybean showed that this fraction plays an important role in plant nutrition.

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  Studying soil phosphorus fractions is useful in understanding soil pedogenesis as well as soil fertility. In this reseach, 20 soil samples were taken from different depths of 0-30 and 30-60 cm of upper-slope, mid-slope and lower-slope positions of four toposequences in arid (Jei and Ziar in Isfahan) and semiarid (Farokhshahr and Shahrekord) regions. In each toposequence, the soil depth was relatively low at the upper-slope position and increased toward the lower-slope. The soils in upper-slope and mid-slope were under scarce native vegetation where the soil in lower-slope was under farming activities. Soil phosphorus (P) fractionation was carried out using sequential extraction. The total soil phosphorus was in the range of 302-1135 with an average of 715 mg/kg. About 65-89% of total phosphorus were inorganic, and 11-35% organic. The amount of inorganic and organic P in the soil samples was in the range of 204-897 with an average of 571, and 70-238 with an average of 114 mg/kg, respectively. The amount of total, inorganic and organic P increased from upper-slope toward the arable lands and decreased from topsoil to subsoil in all toposequences. In the studied soils, apatite ( Ca₁₀-P ), aluminum phosphates(Al-P), octacalcium phosphates( Ca₈-P ), iron phosphates (Fe-P), iron oxides occluded phosphates( OC-P ) and dicalcium phosphates( Ca₂-P ) were the major constituents of the soil inorganic phosphates, respectively.

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Potassium (K) fixation by phyllosilicates clay minerals is a very important process influencing the availability of K for plants. Information about K fixation is limited in Hamadan soils. The objectives of this research were to determine potassium fixation capacity (PFC) and potassium fixation index (PFI) of 10 surface soils of Hamadan province and the correlation of these parameters with soil charge characteristics. Potassium fixation capacity was obtained using six different levels of added K as KCl and three wetting and drying cycles. Also charge characteristics of soils were determined. Tetrahedral CEC of soils was determined after saturation of samples with LiCl and heating at 300 oC to reduce octahedral charge near zero. The results showed that tetrahedral and octahedral CEC ranged from 4.6 to 16.0 and 0.8 to 4.9 cmolckg-1 respectively. Mineral and organic portion CEC ranged from 6.1 to 20.9 and 0.97 to 9.7 cmolckg-1 respectively. The amount of PFC increased with increasing added K. Mean amount of PFC ranged from 58.2 to 175.03 mgkg-1. Potassium fixation index ranged from 0.23 to 0.67. The results of correlation studies indicated that PFI were significantly correlated with octahedral CEC, mineral and organic portion CEC, total CEC, exchangeable and nonexchangeable K. The results of this research showed that PFI very different in soils. So that this parameter should be consider in K soil testing.

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Although the crucial function of earthworms in improvement of soil physical properties is well -know, but very little is known of the interactive influence of earthworms and organic materials on soil properties such as soil aggregate stability, particularly in arid and semi-arid soils. The low organic matter content and the significant role of earthworms in improving physical properties of arid and semi-arid soils necessitate studying the interactive effects of organic materials and earthworms. Thus, the main objective of this study was to identify the interactive effects of anecic earthworm (Lumbricus terrestris L.) and various organic residues (including alfalfa, compost, mixture of alfalfa and compost and cow dung) on soil aggregate stability expressed as the Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD) and Aggregation Ratio (AR), and furthermore soil Ca and Mg contents. The experiment consisted of a 2×5 factorial treatment organized in a completely randomized design with four replications under controlled greenhouse conditions, lasted for 150 days. Results showed that earthworm inoculation and organic materials addition alone increased significantly all the indices of soil aggregation and aggregate stability, and Ca and Mg contents. However, the combined use of earthworms and organic residues resulted in more stable aggregates. Results indicated that earthworm inoculation in the presence of organic materials resulted in 39, 58, 2, 67, 43 and 74% increases, respectively in MWD, AR, GMD, Ca, Mg and macroaggregates whereas microaggregates were reduced by 13.5% in earthworm-worked soils. We observed a significant relationship (R2=0.945) between soil Ca content and MWD, demonstrating that earthworms apparently excrete calcite that helps bonding clay particles and soil organic matter via cationic (Ca+2) bridging. In summary, results of this study show that the simultaneous applications of anecic earthworms and organic materials may considerably help in improving the structure of arid and semi-arid soils with low carbon level.

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The positive and beneficial effects of mycorrhizal symbiosis on the growth of various plants have already been documented. Most arable crops can mutually establish symbiosis with endo-mycorrhizal fungi, however, mycorrhizal associations with almond (prunus amygdalus), particularly in calcareous soils of arid and semi-arid regions, have not been studied. Thus, to realize the symbiotic association between mycorrhiza fungi and economically important native almond genotypes in Chaharmahal va Bakhtiary province, an experiment consisting of a randomized complete factorial design with three factors: almond genotypes (Mamaei, Rabee, Talkh, Sefid), soil phosphorus levels (0 and 150 kg P ha-1) and mycorrhizal treatments (almond inoculated with Glomus intraradices, Glomus mosseae and without inoculation) with three replications was conducted under greenhouse conditions by 4 months. Results showed that physiological traits including chlorophyll concentration, net photosynthetic rate and water use efficiency, were significantly increased for 20%, 300% and 300%, respectively in mycorrhizal almond plants, while transpiration rate was decreased (8-10%). Although the genotype of almond and soil P were dependent on these factors, mycorrhiza species had the same effects. Increased available P in the soil enhanced the growth in all treatments and photosynthesis of nonmycorrhizal almonds.

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The petroleum refinery sludge is an important source of environmental pollution. Burning and burying of the sludge may have adverse effects on environment and human health. Thus, other mechanisms for decreasing the toxic effects of hydrocarbon substances in the sludge must be used. In this study, Isfahan refinery sludge was dewatered, air dried and mixed by 0, 10, 20, 30 and 40% w/w ratio with two calcareous soils, viz., Mahmoud Abad (Typic Haplocalcids with clay texture) and Bagh Parandegan (Anthropic Torrifluvents with silty loam texture). Different mixtures of soil and sludge were farmed for 21 days and irrigated on a daily basis to field capacity. Then, 100 seeds of Tallfescue (Festuca arundinacea) and Agropyron were planted in polluted soils with 3 replicates in 3 kg pots for 5 months. Result showed that Tallfescue and Agropyron yields decreased in sludge contaminated treatments. In the 40% sludge treatment, Tallfescue decreased the total petroleum hydrocarbons content by 65 percent. The highest degradation for agropyron was in the 30% sludge treatment which showed about 55% reduction in total petroleum hydrocarbons. The 40% sludge treatment resulted in the minimum yields of root and shoot plants. The highest degradation of TPHs occurred in the Tallfescue rhizospher of 40% sludge. Maximum degradation of TPHs on the Agropyron rhizospher was in 30% sludge mixed with Bage parandegan soil, but maximum yield of plant was in 20% sludge. Our study shows that Tallfescue rhizospher is most effective for decreasing TPHs, and that the phytoremediation in soils with more clay can adsorb and fix the toxic components and then at higher levels of pollutions can let the plants grow.

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The status of soil K forms and its relationship with K content in wheat grain at harvest period may be important for nutrient fertility management. For this purpose, 40 surface (0-20 cm) and subsurface (20-40 cm) soil samples and also grain samples from wheat fields of Darab region were randomly sampled in 2014. Then physicochemical properties of the soils and the contents of soluble, exchangeable and non-exchangeable K and contents of K in wheat grains were determined. Results indicated that content of soluble, exchangeable and non-exchangeable K in the studied soils ranged 15-70, 91-443 and 396-1182 mg kg^-1, respectively. Significant relationships were obtained between soil K forms and clay, calcium carbonate and CEC. Although it is expected that content of easily available K (soluble and exchangeable K) was low at late stage of wheat growth, most soils had sufficient K content. The positive and significant relationship among different K forms was indicative of the K forms equilibration at the time of wheat harvesting. Although there is not a relationship between K content in wheat grain and soil K forms, it was shown that K content of wheat grain was correlated with soil exchangeable K and clay content in fine-textured soils (clay > 30%). It means that ammonium acetate may be a suitable extractant for estimation of soil K status and plant available K of heavy-textured soils in the studied region.

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