Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 11 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Indole acetic acid and phytase activity produced by rhizosphere bacilli as affected by pH and metals</b>]]> The abilities to produce indole acetic acid (IAA) and mineralize organic phosphorus by phytase are desirable traits in plant-growth promotion rhizobacteria (PGPR) particularly in Chilean Andisols which are characterized by low pH and high total P. However, little is known about the influence of soil properties that are specific to Andisol (low pH and metal toxicity) on the effectiveness of PGPR. Here, we assessed the effect of pH and metal cations on IAA and phytase activity of cell-associated proteins produced by two bacilli strains isolated from the rhizosphere of pasture plants. The production in vivo of IAA by Paenibacillus sp. SPT-03 was significantly increased (7-fold) when incubated in tenfold diluted culture medium, compared to the full-strength medium. At low pH (pH<5), phytase activity of cell-associated proteins and IAA production of Bacillus sp. MQH-19 was decreased, whereas they were increased in Paenibacillus sp. SPT-03. Moreover, phytase activity in vitro of cell-associated proteins and IAA production in both bacilli strains were significantly inhibited by 30-100% and 44-70% by concentrations of 10 mM and 350 μM Fe³+ and Al³+, respectively. At 350 μM Mn²+ IAA production was inhibited by 30-100% in both strains but there was no effect on phytase activity. This study shows that certain properties of Andisol may differentially affect some mechanisms related with PGPR efficiency. <![CDATA[<b>Determination of hydraulic conductivity and fines content in soils near an unlined irrigation canal in Guasave, Sinaloa, Mexico</b>]]> The determination of hydraulic conductivity is essential for the assessment of fluid migration rates in the subsurface. Geoelectric methods are often used in hydrogeological studies as quick and inexpensive tools. The relation between saturated soil hydraulic conductivity (K), clay content and soil resistivity allows an estimation of clay content and K from electrical measurements made in the field or laboratory. In this work, a methodology for estimating fines (silt+clay) content and K from electrical measurements in silt-loam soils is presented. A textural analysis was performed in 73 soil samples collected from 21 boreholes located in the municipality of Guasave, Sinaloa, Mexico, to determine the sections with a greater infiltration of water from the Valle del Fuerte irrigation canal to the local aquifer. The calculated values of texture and K were used to develop a new empirical equation, K = 0.101176 * FINES-1.62, which achieved a new relation to properly estimate the K values from the percentage of fines content. Electrical measurements were performed in the laboratory for each soil sample to determine the fines content. The K values, which were determined by a new empirical equation, showed an acceptable correlation with the values obtained by traditional techniques for silt and silt loam soils with a clay content < 35%. Water resistivity measurements were performed for samples collected from wells and flumes, showing that the water salinity of the canal is significantly lower than the groundwater. Due to the location of the Valle del Fuerte canal and soil K values, the water infiltrated from the flume into the subsoil creates a barrier preventing or slowing down the advance of the saltwater intrusion from the Sea of Cortez. Short Electrical Resistivity Tomography (ERT) profiles were carried out to determine the surface stratigraphy. The results achieved by the application of ERT and the groundwater salinity values allowed the recalculation of the geoelectrical sections in the fines content and K sections, resulting in a new, faster and less expensive procedure for the determination of hydraulic and petrophysical parameters. <![CDATA[<b>Effects of the incorporation of biosolids on soil quality</b>: <b>temporal evolution in a degraded inceptisol (typic endoaquepts)</b>]]> The purpose of this study was to determine the temporal evolution of soil properties following the incorporation of biosolids in a degraded Inceptisol soil (Typic Endoaquepts). The study was conducted in the Araucanía Region of Chile, where two sampling zones were established: a control zone without biosolid incorporation and a zone with biosolid incorporation. Experimental field plots were used to measure soil quality, including soil respiration (SR), infiltration (IN) and bulk density (BD), according to standard USDA methodology. Laboratory analyses of soil chemistry, including pH, electrical conductivity (EC), organic matter (OM), nitrogen (N), aluminium (Al), phosphorus (P) and sulphur (S), were performed using the analytical techniques of the Chilean Society of Soil Science's CNA. Measurements were performed 17, 170, 365 and 510 days after the biosolids were applied. The results indicated significant changes in soil quality 1.4 years after the incorporation of the activated sludge, particularly in sustained increases of phosphorus content, soil respiration and infiltration. In addition, there was a significant increase in the electrical conductivity of the soil, which ranged from normal to high. <![CDATA[<b>Effects of soil amendments on the nutritional quality of okra <i>(Abelmoschus esculentus </i>[L.]Moench)</b>]]> This study examined the effects of different soil amendments [compost organic fertiliser (OR), NPK (IO), Glomus mosseae mycorrhiza (MY) or no soil amendment as the control (CT)] on the nutritional quality and nutrient uptake of okra during cultivation in a field contaminated with sewage sludge from the two oxidation ponds of the Obafemi Awolowo University, Ile-Ife, Nigeria. Okra (Abelmoschus esculentus [L.] Moench) belongs to the Malvacea family. The experiment consisted of a randomised complete block design with four replications. At full physiological maturity, the roots, shoots and pods samples of the okra plants were collected for analyses. The results showed that OR resulted in a significantly (p < 0.05) higher nutrient uptake [N (0.0034 mg kg-1), K (0.0160 mg kg-1), Na (0.9753 mg kg-1), Ca (0.0130 mg kg-1) and Cu (0.01136 mg kg-1)] in the okra roots than in the other treatments, yet the significantly (p < 0.05) highest uptake of P (0.0012 mg kg-1) was obtained with the MY treatment. Lower values of these nutrient contents were obtained in the shoots. The control treatment gave the significantly highest values of crude fibre (27.33%) and total ash (14.05%), as compared to the other treatments, whereas the other nutritional properties obtained showed no significant difference among any of the treatments. The results indicated that high-quality okra pods could be effectively produced with no soil amendment when planted in soils with a high fertility, such as those treated with sewage sludge. <![CDATA[<b>Use of molecular biomarkers in <i>Eisenia foetida </i>to assess copper toxicity in agricultural soils affected by mining activities</b>]]> The agricultural soils in the basin of the Aconcagua River exhibit high concentrations of copper compared with other areas with no mining activity. The objective of this work was to assess the toxicity of such areas on the earthworm Eisenia foetida and its relation to copper concentration using the following molecular biomarkers: glutathione-S-transferase (GST), lipid peroxidation (TBARS) and metallothionein concentrations. These soils were also characterised chemically and physically. The results showed significant differences in the concentration of metallothioneins, TBARS and GST activity. A correlation between pH and copper (total, soluble) with the molecular parameters was observed. Metallothionein and GST are proposed as early warning biomarkers of the toxic effects of chemicals in soils. <![CDATA[Response of "Jonagold" apple trees to Ca, K and Mg fertilization in an andisol in southern Chile]]> The effects of Ca, Mg and K fertilisation on the growth, yield, fruit quality and mineral concentration of the fruits and leaves of 'Jonagold' apple trees that were grown in an Andisol in southern Chile were analysed. In general, the Andisols in this area contain low reservoirs of these elements; therefore, the roles of these elements as essential macroelements and their effects on plant growth, yield and fruit quality are key factors that should be considered in these soils in current and future apple orchards. The soil application of Ca, Mg and K (CaSO4, MgSO4 and K2SO4) did not significantly affect vegetative growth, fruit production or their quality parameters. Ca and Mg fertilisation did not affect the uptake at the present stage of development and production. The mineral concentration of K in the leaves was significantly increased in the plants that were treated with K alone (1.67% DW) or in combination with Ca and Mg (1.8% DW). The fertilisation did not result in the development of physiological disorders in the fruit. This study revealed no relationships between the apple nutrient status and the Ca, Mg and K saturation ratios in the soil. However, the medium to low exchangeable content of these elements in the soil may affect the yields and the quality of the fruit in the future due to the increased demand by the trees for those elements. <![CDATA[<b>Effects of adsorption on degradation and bioavailability of metolachlor in soil</b>]]> The ability of soil to adsorb metolachlor strongly influences its environmental fate, but little information is available on the correlation of its soil adsorption with degradation and bioavailability. The present study was conducted to characterize adsorption, degradation and bioavailability of metolachlor in five soils with different properties, and to investigate the effect of soil adsorption on degradation and bioavailability. Metolachlor was weakly adsorbed to the tested soils with adsorption coefficients ranging from 0.36 to1.18 μg1-n mLn g-1, suggesting its potential to move downward with percolating water. Adsorption followed a Freundlich isotherm and was positively correlated with soil organic matter (OM) content (p < 0.01). Degradation of metolachlor in soils obeyed the first-order kinetics, yielding the half-life varying from 37.9 to 49.5 days, which was significantly influenced by soil OM content (p < 0.01). The prolonged half-life by sterilization indicated that biodegradation was the dominant pathway for metolachlor degradation in soils. Uptake and bioaccumulation of metolachlor in soils by Eisenia foetida was also mainly controlled by soil properties, especially OM. Adsorption coefficients were negatively related to half-lives (p < 0.01) and bioaccumulation factors (p < 0.05), indicating that adsorption coefficients might be useful for predicting degradation and bioavailability of metolachlor in soils. <![CDATA[<b>The effects of CaCO<sub>3</sub> on adsorption, immobilization and activity of cellulase in a decarbonated soil</b>]]> The interaction of organic molecules with mineral surfaces is a subject of interest in a variety of disciplines. The present study was done to elucidate some aspects of sorption and immobilization of cellulase on soil components by analysis of the sorption, desorption, immobilization and activity of cellulase on a decarbonated soil treated with different levels of CaCO3 (0, 2.5, 10 and 20 %). Applied concentrations of cellulase protein on Ca-homoionized soil suspensions were 0, 0.014, 0.028, 0.070, 0.140, 0.280, 0.701, 0.981 and 1.402 mg mL-1. After shaking for 1 h in sterile conditions, they were centrifuged and the amount of the cellulase protein remaining in solution was determined. The adsorbed cellulase protein was calculated. The immobilized and desorbed cellulase proteins were calculated after washing soil suspensions thrice with distilled water. Analysis of variance showed that the effects of the enzyme concentration, CaCO3 level and their interaction on cellulase protein adsorption and activity were statistically significant. The adsorption and immobilization capacities of the decarbonated soil increased by application of CaCO3. However, these effects of CaCO3 were only significant when high concentrations of cellulase protein were added to the soil. The desorption of cellulase protein from the decarbonated soil did not depend on the amount of cellulase adsorbed on the soil and the CaCO3 level in the soil. The immobilized cellulase activity, and particularly its specific activity, decreased considerably by increasing CaCO3 levels in the soil. This negative effect of CaCO3 on the cellulase specific activity in the decarbonated soil was significant even for low levels. <![CDATA[<b>Biochemical and microbiological properties of Argentinean Patagonia soil with implanted forest species</b>]]> The aim of the present study was to determine the effect of two implanted forest species with different vegetal residue chemical compositions on the biological and biochemical properties of soil. The study site was located in the INTA Forestal Station of Trevelin, Chubut, Argentina. Samples were extracted from soil in forest plots dominated by Radiata Pine (Pinus radiata D. Don.) or European Ash (Fraxinus excelsior L.). Microbial respiration, dehydrogenase activity, community-level physiological profile (CLPP) and index of microbial community functional diversity were used as biological parameters; and acid phosphatase, protease and β-glucosidase activities were employed as biochemical parameters. Microbial respiration, dehydrogenase and acid phosphatase activities showed greater values in soil under European Ash trees; however, significant differences in protease and ß-glucosidase activities were not observed among species. The higher organic C content of soil under European Ash trees and lower lignin and greater N and P content of the leaves of European Ash trees could be responsible for the greater biological and biochemical activities observed in the soil. Principal component analysis (for PC1) showed significant differences in the physiology of microbial communities associated with these forest species. The Shannon-Weaver Index (H) of the functional diversity of microflora did not present significant differences among forest species. <![CDATA[<b>Spatial distribution of copper, organic matter and pH in agricultural soils affected by mining activities</b>]]> The Aconcagua River Basin, located in north-central Chile, is an important agricultural region of the country. However, several copper mining industries are also located in this basin. A total of 103 topsoil samples were collected at varying distances from mining industries. There were no statistically significant differences between the sampling areas with regard to organic matter content and copper concentration. However, the sampling areas were significantly different with regard to soil pH. Soils of the Putaendo sampling area exhibited the lowest pH values (mean of 6.3), while the highest pH values (mean of 7.1) were measured in the Catemu - Chagres sampling area. In the sampling areas where mining activities were absent, the total copper concentrations ranged from 70-155 mg kg-1. These concentrations are a result of the geological setting and/or of applications of copper-containing fungicides. High copper concentrations (above 700 mg kg-1, with a maximum of 4000 mg kg-1) were generally observed near mining activities or in areas where mining activities were located nearby and upstream. In these sampling areas, the copper concentrations differed by an order of magnitude in nearby locations. These high and heterogeneously-distributed copper concentrations most likely resulted from either modern or former mining activities.