Bioaccumulation of Nickel and Lead by Bermuda Grass (Cynodon dactylon) and Tall Fescue (Festuca arundinacea) from Two Contaminated Soils

Soil and sediments of the estuaries and wetlands in Northwest of Persian Gulf are recently polluted with different heavy metals because of municipal and industrial wastewaters. Therefore an urgent soil cleaning up and remediation program is vital in this region. Consequently, this study was initiated to screen two plant species (Festuca arundinacea and Cynodon dactylon) for hyperaccumulation of nickel (Ni) and lead (Pb) as one of the candidate methods for cleaning-up soil and sediments of Shadegan wetland. Soil samples (0-30 cm) were collected from two sites in the wetland. The soil samples were treated with solutions of Ni and Pb separately which resulted into content of 50 and 100 mg kg-1 of metals in each soil. Thereafter, the plants were sown in the soils under greenhouse conditions and harvested after 10 weeks. Ni and Pb contents were measured in root and shoot of plants. Results showed that accumulation of Ni and Pb in tall fescue roots were significantly (P<0.05) greater than that in Bermuda grass. The amounts of Pb in root and shoot of plants were increased when soil Pb contents were increased from 50 to 100 mg kg-1 while Ni contents were only increased in the roots in response to increase in soil Ni content. The comparing of the shoot-root ratio showed that Pb accumulation in the roots of both plants was higher than that in the shoots, while for Ni was reverse. Due to difference in backgrounds of soil metal contents and soil characteristics, accumulation of Ni and Pb by plants were different in two soils

Heavy Metals Extraction Potential of Sunflower (Helianthus annuus) and Canola (Brassica napus)

Phytoextraction is a remediation technology that uses plants to remove heavy metals from soil. The success of a phytoextraction process depends on adequate plant yield (aerial parts) and high metal concentrations in plant shoots. A pot experiment was conducted to investigate the combination effects of plants [sunflower (Helianthus annuus) and canola (Brassica napus)] with soil treatments (manure, sulfuric acid and DTPA). Treatments, included two plants and seven soil treatments, which were applied baeed on a completely randomized factorial design. Three replicates were used for each treatment.. The largest shoot dry weight biomass production occurred in manure treatments for both plants. The maximum shoot concentrations of Pb and Zn were 234.6 and 1364.4 mg kg-1 respectively in three mmoles DTPA kg-1 treatment of sunflower. Furthermore the results showed that sunflower had a higher extracting potential for removal of Pb and Zn from polluted soil

Effect of Acidic Biochars on Some Chemical Properties and Nutrient Availabilities of Calcareous Soils

Low organic matter content and alkaline pH of calcareous soils in arid and semi-arid regions are the main reasons for the low nutrient availabilities for plants in these soils. One way to improve the chemical properties and fertility of calcareous soils is the application of organic substances such as biochar produced from pyrolysis of organic wastes. However, biochars have an almost predominant alkaline pH, which exacerbates plant nutrient deficiencies in calcareous soils when used for a long time. Pyrolysis of some organic wastes under controlled temperature conditions can lead to the production of acidic biochar. The effect of acidic biochars on several chemical properties of two calcareous soils in Isfahan province was investigated in the present study. Treatments included two types of biochar (pine cone and rice husk), three levels of biochar addition (one, three, and six percent), two types of soil (a sandy loam (Tiran) and a clay loam (Lavark)), and two incubation periods (one and six months). The results showed that applying biochar could slightly decrease soil pH but raised soil electrical conductivity. In addition, the amount of organic carbon, total nitrogen, and available concentration of manganese in all treatments and the concentrations of available phosphorus, potassium, iron, zinc, and copper in the most of treatments showed a significant increase compared to the control. Amending soil with biochar at a 6% rate caused the most significant changes in the measured parameters in both soil types. In general, the results of this study indicated that acidic biochar produced from pine cones and rice husk can be used as a suitable conditioner to improve the chemical properties and fertility of calcareous soils

Comparisons of different procedures of pre-compaction stress determination on weakly structured soils

Compaction is an important component of soil degradation. In this regard, the pre-compaction stress (sigma(pc)) concept is considered useful in mechanized agriculture nowadays. When the external forces exceed the internal strength (sigma(pc)) of soil, soil structure and soil physical quality will deteriorate. This concept was introduced at first for confined consolidation of non-structured, homogenized and saturated subsoils in civil engineering, though it is also suitable for agricultural conditions where the topsoil and subsoil are considered and both are often structured, heterogeneous and unsaturated. The best method for predicting up, is by the plate sinkage test (PST) in the field, but it is expensive and time-consuming. This study was conducted to find an alternative laboratory method besides the confined compaction test (CCT) for predicting sigma(pc). The CCT may not be a good method, especially at higher water contents, and for soils with low organic matter content, because of low sharpness of the critical region on the stress-strain curves. The study was performed on five soil types with a range of soil textures and organic matter content from central Iran using three loading types and three pF (i.e. Log [soil matric suction in cm]) values of 2.3, 2.7 and 2.9 with two replicates. Loading types consisted of CCT, the semi-confined compaction test (SCCT) and the kneading compaction test (KCT) at three maximum (or pre-compaction) stresses of 200,400 and 600 kPa. The experiment was a completely randomized factorial design. The aim was to determine how accurately each loading type test could predict UPC of soil pre-compacted by one of the other methods. The applied combinations of CCT-SCCT, SCCT-CCT and KCT-CCT mean that the soil was pre-compacted by the first loading type and evaluated by the second one. The results showed that sigma(pc) and the sharpness of the sigma(pc) region were significantly affected by loading types as well as the soil conditions. The sharpest up, region was observed in SCCT and the least sharp in CCT with the overall order being CCT-SCCT > SCCT-CCT > KCT-CCT. The sharpness of the UPC region was reduced for the soil samples with higher water content and coarser texture. Regardless of the soil and loading conditions, the prediction by SCCT was consistently more accurate than by CCT. The prediction of up, by SCCT was more precise in comparison with CCT especially at higher stresses and soil water contents. However, the prediction of UPC by SCCT was very accurate at pF values of 2.7 and 2.9, and with low UPC values, when compared with the actual values of the sigma(pc). For the clay soil at a pF value of 2.3, no pre-compaction region (i.e. zero sigma(pc)) could be determined by CCT at a maximum axial stress of 600 kPa. This was because of the incompressibility of soil water at this near-saturated soil condition at high stress. However, the sharpness of the critical region in SCCT was high enough to predict up, satisfactorily. There was no significant difference between the combinations of SCCT-CCT and KCT-CCT in predicting up,. The SCCT is a compromise method that lies between CCT and PST. SCCT has the advantage of using a limited and definite soil volume that can be modeled as a soil element. Marginal effects of disturbance caused by coring/sampling as well as pre-test sample preparation seem to have minor effects on the stress-strain curve determined by SCCT in comparison with CCT. Moreover, the soil volume needed for this tet is the same as for CCT. (c) 2006 ISTVS. Published by Elsevier Ltd. All rights reserved

Suitability of pre-compression stress as the real critical stress of unsaturated agricultural soils

This study was conducted to examine if the pre-compression stress sigma(pc) is the major critical stress influencing soil physical quality indices, i.e. air permeability K-g and air-filled porosity (AFP). Topoils of five soil series were collected from the Isfahan Province in central Iran. Treatments consisted of: five soil types (sandy loam to clay), four matric suctions (10, 20, 50 and 80 kPa), three values for the maximum axial stress sigma(pc) (200, 400 and 600 kPa), and three loading types with 10 loading cycles. The loading types were a confined compression test (CCT), a semi-confined compression test (SCCT) and a kneading compression test (KCT). Soil type and matric suction, loading type, maximum applied stress and number of loading cycles significantly affected log [K-g], void ratio e, and AFP. The Significance of the loading cycle's number implies that though the up, of the soil was not exceeded, the soil physical properties were considerably changed. A gradual transition from elastic-to-plastic deformation was observed on the stress-strain curves obtained from CCT. The stress-strain curves of the SCCT were sharp at sigma(pc) due to the semi-confined condition, which allows lateral deformation during loading. Cyclic loading was not always accompanied by significant irreversible strain but this could result in up to 10 times the decrease in K-g. For the fine-textured soils, CCT resulted in a significantly greater reduction in K-g, a and AFP when compared with KCT. The opposite trend was observed for the coarse-textured soils. The KCT homogenised the pore system and resulted in more decrease of K-g when compared with CCT at matric suctions of 10 and 20 kPa. However, at the matric suctions of 50 and 80 kPa, KCT created an open microstructure, which led to relatively higher values of K-g. The results show that the sigma(pc) might not be a real critical stress from a view of soil physical quality indices (i.e. K-g and AFP), especially at low matric suctions. Thus, the characterisation of soil compaction may not be completely accounted by a bulk property such as void ratio, but additional information about pore characteristics are needed to describe the effect of compaction on soil physical quality. (c) 2007 IAgrE. Published by Elsevier Ltd. All rights reserved

Prediction of soil physical properties by optimized support vector machines

The potential use of optimized support vector machines with simulated annealing algorithm in developing prediction functions for estimating soil aggregate stability and soil shear strength was evaluated. The predictive capabilities of support vector machines in comparison with traditional regression prediction functions were also studied. In results, the support vector machines achieved greater accuracy in predicting both soil shear strength and soil aggregate stability properties comparing to traditional multiple-linear regression. The coefficient of correlation (R) between the measured and predicted soil shear strength values using the support vector machine model was 0.98 while it was 0.52 using the multiple-linear regression model. Furthermore, a lower mean square error value of 0.06 obtained using the support vector machine model in prediction of soil shear strength as compared to the multiple-linear regression model. The ERROR% value for soil aggregate stability prediction using the multiple-linear regression model was 14.59% while a lower ERROR% value of 4.29% was observed for the support vector machine model. The mean square error values for soil aggregate stability prediction using the multiplelinear regression and support vector machine models were 0.001 and 0.012, respectively. It appears that utilization of optimized support vector machine approach with simulated annealing algorithm in developing soil property prediction functions could be a suitable alternative to commonly used regression methods

Doses de fósforo e crescimento radicular de cultivares de arroz de terras altas Phosphorus doses and root growth of upland rice

O estudo de crescimento radicular de arroz de terras altas em função da disponibilidade de fósforo é, praticamente, inexistente. O objetivo deste trabalho foi avaliar o crescimento de diversas cultivares de arroz de terras altas em diferentes condições de disponibilidade de fósforo. O experimento foi desenvolvido em casa de vegetação, em delineamento inteiramente casualizado, em esquema fatorial 4 x 4, com quatro doses de P (0, 50, 100 e 200 mg dm-3) e quatro cultivares: Maravilha (grupo moderno), IAC 201, IAC 202 e Carajás (grupo intermediário). A cultivar Carajás possui sistema radicular que melhor se desenvolveu sob baixa disponibilidade de P. Sob baixa disponibilidade de P as cultivares IAC 201 e IAC 202 priorizaram o desenvolvimento do sistema radicular em relação a parte aérea. A cultivar Maravilha requer níveis elevados de fósforo para atingir o máximo desenvolvimento. Sob baixa disponibilidade de fósforo as cultivares de arroz diminuíram o diâmetro radicular.<br>Very little is known of phosphorus availability for upland rice. The objective of this work was to evaluate root growth of upland rice cultivars in different conditions of phosphorus availability. The experiment was carried out in greenhouse, in a completely randomized design, as a 4 x 4 factorial, with four doses of P (0, 50, 100 and 200 mg dm-3) and four cultivars: Maravilha (modern group), IAC 201, IAC 202 and Carajás (middle group). The Carajás root system grew more in low availability of P than other cultivars. In low availability of P the cultivars IAC 201 and IAC 202 priorized root system growth to aerial growth . The Maravilha cultivar needs high Plevels to reach maximum growth. In low availability of P the upland rice cultivars decreased root diameter