APPLIED SOIL RESEARCH
Year:2017 | Volume:5 | Issue:1|Papers Count:10

Soil pollution by heavy metals like cadmium (Cd) with lowering the activity of microorganism can change carbon sequestration in soil. Plant residues when applied in soil are in free particulate form. They will be covered by clay particle and finally will be transformed to organ mineral particles biologically. In this study, the effects of Cd addition (0 and 10 mg kg-1 soil) and time duration (1 day, 1, 3 and 5 months) on particle size fraction of organic carbon (OC) were studied in Hmadan and Lahijan soils in 3 replicates. Sand size fraction (SSF) and silt+clay size fraction (Si+CSF) of soil organic carbon were analyzed by the particle size fractionation and OC determination by wet oxidation. The main part of OC in Hamadan soil was in SSF (14.12 mg kg-1 soil or 40%) but it was in Si+CSF in Lahijan soil (15.80 mg kg-1 soil or 32%) in 1st day of soil incubation. The rate of OC decrease in Hamadan soil was markedly higher than that in Lahijan soil. Soil pollution with Cd decreased OC biodegradation in both of the studied soils. It increased OC retention especially in Lahijan soil. This effect may be related to higher clay content and higher Cd bioavailability and contamination factor in Lahijan soil.

Potassium and nitrogen are two major nutrients, have important role in increasing rice quantity and quality. Potassium like nitrogen is taken up in large amount by rice. Evaluation of nutrient status in soil is important from nutritional, environmental and economic aspects. This study was conducted in order to evaluate 11 different chemical extractants for determining suitable extractants for estimation of available potassium of rice in 11 selected soils of Kohgiluyeh Province. Rice seeds were cultivated in 1.5 kg pots in three replications and harvested after 10 weeks. Plant potassium was extracted with 1N HCl. Soil available potassium was extracted using 1M NH4OAC, 1 and 2M sodium chloride, 0.025 M sulfuric acid, 0.1M barium chloride, 0.01M calcium chloride, Morgan-Wolf, AB-DTPA, 1N NaOAC, 1M magnesium acetate and 2M Hydrochloric acid. The amount of K extracted by 1N NaOAC and 1N NH4OAC, was significantly (r=0.85** and 0.73**, respectively) correlated with K concentration, followed by Morgan and 2N NaCl. The lowest correlation is belonged to 1N HCl. Therefore, due to the simplicity and economy, the rate of extraction and the high correlation, extractants of 1N NaOAC and 1N NH4OAC are recommended as suitable extractants for determining the available K uptake by rice in the soil studied.

Potassium and phosphorus are essential elements for plant growth, and application of biological methods is one approach to supply them. This study was done, in order to evaluate the effect of soluble source of phosphorus (phosphate sodium) and insoluble (tricalcium phosphate or TCP) on K release from mica minerals (biotite and muscovite) and also the effect of mica minerals in dissolution of phosphorus from tricalcium phosphate. This test was carried out in the presence of some bacterial isolates belonging to the genus Pseudomonas (S10-3, S14-3, S19-1 and S21-1). It was conducted as a factorial experiment based on completely randomized design with three replications containing two factors including two source of phosphorus and two potassium sources. From overnight cultures of the bacteria (0.5 ml) were added to 30 ml of Aleksandrov medium. After incubation for one week at 26 °C and shaking at 120 rpm, released K in supernatant was measured by using flame photometer and the dissolution of phosphate recorded at 430 nm by spectrophotometer (yellow method). The results showed that K releasing from the biotite was more than muscovite and bacterial isolates released more potassium (in average 15-48%) in the presence of TCP than sodium phosphate. The isolate S19-1revealedhighest potassium releasing (5.45 mg l-1). The results displayed that there leased potassium from biotite was higher than muscovite (4.5times). Biotite and muscovite minerals did not significantly affect the phosphate solubilization and the highest phosphate solubilization (488 mg l-1) was obtained by S19-1.Mica minerals did not affect P solubility behavior of isolates but K releasing from mica minerals was increased in the presence of insoluble phosphate (TCP).

In order to study the changes in different fractions of Zn, Cu, Cd and Pb during the vermicomposting process of cattle manure, an experiment was conducted based on completely randomized design with factorial arrangement replicated three times. The first experimental factor was presence and absence of earthworm, and period of vermicomposting (0, 30, 60 and 90 days) was taken into account as the second factor. A five-step sequential extraction procedure recommended by Tessier was used for fractionation of Zn, Cu, Cd and Pb during the process of vermicomposting of caw manure. The exchangeable, carbonate-bound, Fe-Mn oxides-bound, organic matter-bound and residual fractions of metals were determined using atomic absorption apparatus (FAAS, Thermo element MK-M6). The results showed that pH of vermicompost decreased 0.4 of unit and dissolved organic carbon (DOC) increased 0.15 percent in treatments of with worm. The bioavailability of Zn, Cu and Cd, not Pb increased significantly in the compost samples. Following earthworm activity, the highest content of Zn, Cu and Cd were observed as bounded by carbonate, organic matter and exchangeable fractions, respectively, while the most amount of Pb was found in organic band fraction. Zn and Cd concentrations in carbonate and exchangeable fractions significantly increased in earthworm treatments, Zn 16.4 and 18.21 percent and Cd 10 percent increased in this fractions, however the concentration of those in residual fraction decreased by the end of incubation period. It is concluded that earthworm activity increases the bioavailability of some of metals (Cd, Zn, and Cu) during the vermicomposting process.

In order to study the effect of man-made tree covers on soil biological and biochemical properties, the forest stands ofRobinia pseudoacacia, Fraxinus excelsior, Quercus castaneifolia and Cupressus arizonica were considered in the forest park area of Khargoosh-dareh located in Tehran. In each tree covers, 10 soil samples were taken from topsoil (0-10 cm depth). Soil biological, biochemical and also some physico-chemical properties were measured at the laboratory. According to our data, none of soil physical characrteristics were significantly affected by tree covers. The soil under C. arizonica was more acidic compared with Q. castaneifolia, F. excelsior and R. pseudoacacia stands. Greater amounts of soil N, available P and K were found under R. pseudoacacia stand (0.33%, 26.21 and 349.80 mg/kg respectively) and the least was measured under C. arizonica tree cover (0.10%, 12.76 and 145.30 mg/kg respectively). The higher values of root biomass (fine root, coarse root and total root) were recorded under Q. castaneifolia species (950.21, 1079.90 and 1692.54 kg/ha respectively) whereas, the minimum values were found under C. arizonica trees (402.24, 755.60 and 1157.84 kg/ha respectively). The greater amounts of soil nitrification rate, ammonification rate and net N mineralization were found under R.pseudoacacia(-0.13, 0.44 and 0.30 mg/kg respectively) and the least was measured under C. arizonica tree cover (-0.18, -0.07 and -0.26 mg/kg respectively). Based on our findings, the R. pseudoacacia as N-fixing tree species, presented better performance in soil quality improvement compared with the other studied spcies.

Fuzzy sets are classes without sharp boundaries; that is, the transition between membershipand non-memberships of a location in the class is gradual. A fuzzy set, is described by a fuzzy membership functions that range from 0.0 to 1.0, representing a continuous increase from non-membership to complete membership.Additionally, membership function is one of important factors on land suitability evaluation by fuzy set theory. The goal ofthis research was the coparison of three membership functions in land suitability by fuzzy set theory in East Amol region for irrigated rice. In order to achive to this goal, 8 properties were selected based on FAO framework approach and then land suitability evaluation was done on 17 land units of study area. The results indicated that climate had higher and cation exchenge capacity had lower weights than other criteria in study reigin for the growth of irrigated rice. Calculated correlation coefficients between land index and observed production by fuzzy method with kandel membership function was (r=0.98) more than Cauchy (r=0.75) and Trapezoidal (r=0.79) Membership function and relatively large difference in calculated correlation coefficient had been identified in candele membership function provides better results than others. Additionally, matlab software correctly predicted oweral weithing of this method based on transitional range. Finally, it could be expressed that the appropriate membership functions and transition range in fuzzy set theory can be used as an efficient method in land suitability evaluation.

Probability mapping of soil proprieties Including soil organic carbon and nutrients based on threshold values play important role in optimum land management and sustainable agriculture development. In order to map based on critical limits need to use non parametric geostatistics methods such as kriging indicator. In this study, using indicator kriging, probability map of deficiency or excess of soil available phosphorus and organic carbon was prepared in part of Eslamabad-e Gharb agriculture research station in Kermanshah province. The soil legacy data including 217 surface soil samples on an almost regular grid, about 50 m apart is used to perform research. After preliminary statistical processing, indicator variogram was drawn based on threshold values 1.2% and 15ppm for soil organic carbon and available phosphorus, respectively. Exponential model as the best model fitted to indicator variogram is selected based on minimum residual sum of squares. The necessary data for validation was achieved through leave-one-out cross-validation (LOOCV).For assessing the performance of indicator kriging is used the area under the curve (AUC) of receiver operating characteristic (ROC). Area under the ROC curve was calculated for phosphorus and soil organic carbon was 0.796 and 0.800, respectively. These results indicated that the indicator kriging to predict these variables have relatively good performance. In general, it can be said that using fertilizer based on probability maps of soil fertility properties lead to reduce cost and increase sustainable food production.

The use of bio-fertilizers is a global approach to reduce chemical inputs pollution to increase the quantity and quality of plant products in line with sustainable agriculture. In this study in order to compare the effects of biological and chemical phosphorus fertilizer on phosphorus uptake and yield of ornamental calendula, a factorial experiment with two factors: 1 - Application of biological phosphorus fertilizer at four levels: M1 (without using biological phosphorus manure), M2 (inoculated seed with biological phosphorus fertilizer), M3 (inoculated roots with biological phosphorus fertilizer), M4 (inoculated seed and roots with biological phosphorus fertilizer) and (2) the amount of phosphorus in the form of triple superphosphate at four levels P1 (zero), P2 (100), P3 (200), P4 (300 mgl-1), based on a randomized complete block design with 16 treatments and 5 replicates with 5 pot per treatment was performed. The results showed that of the biological phosphate fertilizer application methods, M4 to most of the traits such plant height (35.53 cm), flower diameter (66.58 mm), flower number (9.15), number of leaves per plant (64.25), shoot fresh weight (29.9 g) and shoot P (% 3.45) was effective and efficient and phosphorus fertilizer consumption has reduced. Whereas in most of the characteristics M4P3 treatment had no significant difference with M4P4 treatment. Therefore, it is advisable to reduce consumption of chemical phosphorus fertilizer.

Chemical, bio and organic fertilizers have an important role in increasing of quantity and quality of agricultural products. In order to study the effects of mycorrhizal inoculation, potassium and organic manure applications on the yield and chemical composition of pomegranate leaves, a factorial experiment in a randomized complete block design with three replications was conducted, in Jannatshahr region, located nearby Darab at Fars province in 2013, . Treatments were a combination of two levels of 0 and 500 grams of mycorrhiza, three levels of 0, 10 and 20 kg sheep manure and two levels of 0 and 500 g of potassium oxide per tree. Mycorrhizae and sheep manure were used before flowering and potassium was applied before and after flowering. The measured factors were yield per tree, fruit weight, skin weight, grain weight, grain skin than five fruits and concentration of potassium, phosphorus, iron, manganese, zinc and copper in leaves. The results showed that the main effects of mycorrhiza, potassium and manure application on the most of studied characteristics were significant. The highest average weight of 5 fruits, the highest kernel weight and the lowest skin-to-kernel weight ratio were obtained from combined application of 500 grams mycorrhizal, 20 kg of manure and 500 g of K2O. The maximum concentration of potassium, phosphorus, iron, copper, manganese and zinc were obtained from combined use of 500 grams of mycorrhiza, 500 grams K2O and 20 kg of sheep manure per each tree.The highest yield of pomegranate fruit (44 kg per tree) were obtained from combined application of 500 g mycorrhiza, 10 kg of sheep manure and 500 g of K2O, which compared with the control treatment, showed 127% increase in yield and can be recommended as the superior treatment.

Improvement of saline-sodic soils is very important in terms of soil and water resources conversation. Accumulation and increasing of soil salts prevents plant growth and directly affects the crop yield. Soil salts reduction through the leaching and preventing from water logging is among the most important steps to prevent the negative effects of soil salinity. Improvement of saline-sodic soils depends on the quality and amount of applied water, type of amendment material and soil drainage condition. In this study, in order to evaluate how to improve the saline and sodic soils, randomized complete block design were conducted with different leaching treatments by using acidic and pure water in three levels of 25, 50 and 75 cm with three replications. After the soil moisture content reached to field capacity, soil samples were taken to analyze the changes of soil salts. Results indicated that, soil salinity and alkalinity class changed from S3A2 (high salinity and relatively high alkalinity) to S1A1 (low salinity and alkalinity) after leaching. The lowest and highest percentages of salinity and alkalinity improvement were related to the 25 cm of pure water and 75 cm of acidic water treatments, with average reduction of 24.7 and 41.2 percent for exchangeable sodium (ESP) and 25.9 and 69 percent for electrical conductivity (EC), respectively. In all treatments, differences between the use of the pure and acidic water were significant. This suggests that the amendment material is effective. Statistical analysis of results showed significant changes in ESP and EC parameters in 5 and 1 percent levels, respectively. Application of 50 cm acidic water was recognized as the most appropriate treatment in terms of water use and leaching efficiency. It could be recommended that, for efficient use of applied water, 50 cm acidic water to be used for remediation of soils in this region.