Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> http://www.scielo.cl/rss.php?pid=0718-951620160003&lang=pt vol. 16 num. 3 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>Analysis of plant growth promoting potential of endophytes isolated from <i>Echinacea purpurea</i> and <i>Lonicera japonica</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300001&lng=pt&nrm=iso&tlng=pt Plant endophytes help in maintaining plant health by means of their biofertilizer and biocontrol attributes and, are currently being explored for their ability to produce novel biologically active compounds. Herein, we have isolated beneficial endophytic bacteria from Echinacea purpurea (EF.B3) and Lonicera japonica (LS.B11) that showed phosphate solubilization, siderophore, indole acetic acid and hydrogen cyanide production, and fixation of atmospheric nitrogen. Additionally, the endophytes also conferred antifungal activity against Fusarium sp., Rhizoctonia sp., Pythium sp. and Alternaria sp. When tested in plantae, the LS.B11 and EF.B3 strains were able to promote plant growth and control fungal infections in peaseedlings. Both strains were found to be endophytic as tested by RAPD and viability count. Based on 16S rRNA gene sequencing, we show that the LS.B11 and EF.B3 strains are related to Pseudomonas sp. And Burkholderia sp. By using degenerate primers, we identified genes related to polyketide synthases and non-ribosomal peptide synthetases in EF.B3 and LS.B11, respectively that are typically involved in the production of antimicrobial compounds. Therefore, we conclude that both endophytes can be used for increasing agriculture productivity and in the production of antimicrobial compounds for crop improvement. <![CDATA[<b>Identification of plant growth promoting Rhizosphere <i>Bacillus</i> sp. WG4 antagonistic to <i>Pythium myriotylum</i> and its enhanced antifungal effect in association with <i>Trichoderma</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300002&lng=pt&nrm=iso&tlng=pt Among the various rhizospheric bacterial isolates screened from Westren Ghat regions of Kerala, a Bacillus sp. with both antagonistic activity to Pythium myriotylum and plant growth promoting properties was identified. Scanning electron microscopic analysis revealed significant ultrastructural changes of hyphae and spores of P. myriotylum upon treatment with Bacillus sp.WG4. For the structural characterization of antagonistic compound in the crude exract, GC MS analysis was carried out and this has resulted in the identification of presence of pyrrolo [1,2- a] pyrazine-1,4-dione, hexahydro-3-(phenylmethyl) as basis of antifungal activity. The in vivo antifungal activity of Bacillus strain was analysed by pre-inoculation of this to ginger rhizome. Here the presence of Bacillus strain was found to provide effective protection to ginger rhizome upon inoculation with Pythium myriotylum. Very interestingly, when the Bacillus strain was checked for its synergistic antifungal activity with commercially available biocontrol agent Trichoderma, the combination was found to have increased antifungal activity. Due to its antifungal and growth enhancement effects, the isolated strain can be of promising application as antifungal plant probiotic agent alone or in combination with other agents like Trichoderma. <![CDATA[<b>Maize nitrogen recovery and dry matter production as affected by application of solid cattle manure subjected to various storage conditions</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300003&lng=pt&nrm=iso&tlng=pt This study aimed to quantify the effects of contrasting composted methods of solid cattle manure (SCM) ondry matter (DM) yield and crop apparent N recovery (ANR)following manure application to maize land. Fresh SCM was stored as stockpiled, roofed, covered and composted heaps. After storage, the manures were incorporated in a sandy soil, and maize ANR both as a proportion of field applied N (ANR F) and collected N from the barn (ANR B),and DM yield was established at three successive growth stages: end of juvenile phase, start of grain filling, and physiological maturity. During the storage period, on average 6% of the initial Ntotal was lost from covered, whereas this fraction was 12, 21 and 33% from roofed, stockpiled, and composted heaps, respectively. DM yield of maize increased with the application of all the manure types as compared to the unfertilized control, at the end of Juvenile (2.2 vs. 3.1-3.4 Mg ha-1), grain filling (11.2 vs. 13.6-16.4 Mg ha-1) and physiological maturity stages (13.9 vs. 15.3-15.9 Mg ha-1). At a given growth stage, the greatest value was obtained from covered than roofed, stockpiled and composted manures.Maize ANR F was the highest at start of grain filling (20, 29, 31, and 39% of the applied N for composted, stockpiled, roofed and covered treatments, respectively) but lower values were obtained at physiological maturity (12-21%). The respective values in case of maize ANR B were 13, 23, 27 and 37% of total N taken from barn at the start of grain filling while it was also lower (8-20%) at physiological maturity. It is concluded thatstorage of SCM under an impermeable plastic cover reduce N losses, increased DM yield and ANR thereby improves on-farm N cycling as compared to traditional stockpiling or composting. <![CDATA[<b>Effect of saline irrigation water on the leachability of salts, growth and chemical composition of wheat (<i>Triticum aestivum</i> L.) in saline-sodic soil supplemented with phosphorus and potassium</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300004&lng=pt&nrm=iso&tlng=pt Salinity-fertility interaction has not been properly explored especially in saline-sodic soils. Therefore, the current study investigated the response of wheat (Triticum aestivum L.) to saline irrigation water in saline-sodic soil supplemented with potassium (K) and phosphorus (P). Wheat was grown in pots filled with saline-sodic soil which were irrigated either with normal or saline water. Potassium and P fertilizers were applied at two levels. Results indicated that growth of wheat plants was impaired by saline irrigation resulting in a decreased grain and dry matter yield. The P application had significant effect on the dry matter yield and other yield components. Potassium application significantly increased dry matter yield and root mass. Wheat yield increased by 14 and 7% with the application of 150 kg K2O ha-1 and 120 kg P2O5 ha-1 over the control soil under saline irrigation. The higher yield was obtained with combined P and K treatment under non-saline irrigation. The P addition significantly affected shoot and root [P] and [Na], [K] and [Mg] in the shoot tissue while the K:Na ratio produced non-significant effects under both irrigation waters. The addition of K significantly affected [Na], [K] and K:Na ratio in shoot. All other root parameters were significantly affected by the K addition. The Ca uptake by roots increased with saline irrigation. The P addition increased [P] in plant tissue. The Na uptake by root and shoot tissues was depressed with the addition of P and K fertilizers. The higher K uptake increased K:Na ratio in both shoot and root tissues. The values of EC, SAR and [P], [Na], [Ca], [Mg], [Cl] and ratios of Na:K, Ca:P, Cl:P and SO4:P in the soil leachates significantly increased with saline irrigation. The P addition had significant bearing on the soil pH, SAR, [P], [SO4], [CO3] and [HCO3] and Ca:P, Cl:P and SO4:P ratios in leachates. Saline irrigation significantly increased ECe, [Na], [K], [Ca], [Mg], [Cl], [CO3], SAR and ratios of Ca:P, Cl:P and SO4:Cl in saturated extracts of post-harvest soils. This study could suggest that the addition of P and K under saline-sodic conditions may affect salts and nutrients dynamics of the soil and was useful for crop productivity. <![CDATA[<b>Response of</b> <b>pomegranate</b> <b>cv. wonderful plants</b> <b>t</b><b>ο</b><b> salinity</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300005&lng=pt&nrm=iso&tlng=pt Three salts (NaCl; KCl; Na2SO4) were supplied to pomegranate cv. Wonderful plants, in order to investigate their effects on growth, nutrient status, chlorophyll, total carbohydrate content and antioxidant defense system. In general, high salt supply led to a significant decline in total N and K content of plants. Also, all salt treatments decreased Ca and Mg concentration of leaves. Both NaCl and KCl treatments increased leaf Cl concentration by up to 418%. Salt excess resulted in a significant decline of chlorophyll and carbohydrate concentration of leaves and/or roots. Finally, concerning antioxidants, diamine oxidase activity increased in the treatment of 120 mM Na2SO4. In conclusion, salinity impaired mineral nutrition of pomegranate cv. Wonderful. On the other hand, that cultivar presented mechanisms that alleviated the detrimental effects of salinity. Therefore, the studied plants, even under high saline treatments, managed to maintain water content, chlorophyll fluorescence and enzyme activity in normal levels. These results suggest that ,Wonderful, may be cultivated under saline conditions provided that a suitable fertilization program is used. <![CDATA[<b>Effects of new coated release fertilizer on the growth of maize</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300006&lng=pt&nrm=iso&tlng=pt Slow or controlled release fertilizers have been researched and used more and more widely, developing new slow or controlled release fertilizers is very important. To improve the use efficiency of inorganic fertilizers through the use of coated fertilizer and nitrification inhibitors, 3 newly developed fertilizers (FCRF1:coated fertilizer + 1% DCD, FCRF2: coated fertilizer + 2% DCD and FCRF3:coated fertilizer + 4% DCD) amended with nitrification inhibitors (DCD, C2H4N4), and coated with fly ash were prepared by coating conventional compound fertilizer (N-P-K: 15-6.55-12.4). Using a coated fertilizer (resin coated compound fertilizer, N-P-K: 15-6.55-12.4, 90 day, CRF) made in China and a conventional compound fertilizer (CCF) as checks, their effects on physiological characteristics, yield and quality of maize were examined in a field experiment. The results indicated that, compared to CCF, 3 new developed fertilizers kept higher ammonium nitrogen (NH4+-N)and nitrate nitrogen (NO3--N) content at later stages and FCRF3 had the highest content, being similar to CRF treatment. At tasselling stage (TS) and filling stage (FS), the chlorophyll content, photosynthetic rate, transpiration rate and chlorophyll fluorescence parameters were significantly increased upon FCRF1, FCRF2 and FCRF3 treatments. In addition, FCRF1, FCRF2 and FCRF3 treatments produced 24.0-35.8% more grain yield, 57.2%-74.4% more total yield, increased 11.20%-49.55% starch, 61.38%-113% protein and 2.67%-9.33% Vitamine C content than CCF,respectively. This product with excellent slow release capacity, being easy to get at a low price and environment-friendly, could be especially useful in agricultural application. <![CDATA[Optimal harvest timing of <i>Prangos ferulacea</i> (L.) Lindl: <strong>effects of phenology stages, elevation and type of plant factors on forage quality </strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300007&lng=pt&nrm=iso&tlng=pt Prangos ferulacea ;(L.) Lindl (Umbelliferae) is a forage and medicinal plant that grows in central Asia. This study was carried out to determine the nutritive value of P. ferulacea, which is often used as animal fodder. Plant samples collected from two elevation levels (2200- 2900 m) of western Iran were evaluated at two stages of maturity, flowering and seeding stage for fertile plants and at 42 and 62 days after leaf emergence for infertile individuals. The nutrient composition, including metabolizable energy (ME) and digestible dry matter (DMD), crude protein (CP), water-soluble carbohydrate (WSC), acid detergent fibre (ADF), natural detergent fibre (NDF) and crude fibre (CF) contents were measured by near infrared reflectance spectroscopy (NIRS) technology. The stage of maturity and type of plant (fertile and infertile) were significantly related to the CP, ME, NDF and ADF contents. Based on multivariate analysis (two-way ANOVA), the phenology, individual and phenology × individual interaction factors had the highest effect on nutrient composition parameters. Based on our findings, we proposed that infertile plants at 42 days after leaf emergence stage represent the best quality fodder. Elevation level did not significantly affect forage quality. <![CDATA[<b>Modulation of antioxidant enzymes by salicylic acid in arsenic exposed <i>Glycine max</i> L.</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300008&lng=pt&nrm=iso&tlng=pt To investigate the physiological and metabolic attributes of arsenic (As) stress tolerance conferred by exogenous salicylic acid (SA), Glycine max L. (variety JS 335) seeds were aseptically germinated over filter paper moistened with SA (500 µM) and/or10 and 100 µM As (Sodium arsenite was used). On 2nd and 5th days of germination, the growing radicles were harvested, and analyzed for growth and different metabolic attributes. Findings exemplified that As significantly decreased germination percentage, radicle length, dry mass and activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), while stimulated the contents of As, reactive oxygen species (ROS), lipoxygenase (LOX), guaiacol peroxidase (POD) and proline. Additionally, isozymes of antioxidants were also scrutinized over Native-PAGE gels and were found to be altered considerably under As-stress. However, exogenous SA remarkably enhanced germination percentage, growth indices, activities of SOD, CAT and APX, and proline accumulation along with reduced As, ROS and LOX, and restoring POD in As-stressed seedlings. In conclusion, SA confers As-stress tolerance to Glycine max L. by regulating the antioxidant enzymes and proline accumulation thereby reduced As content and ROS production. Further study is intended, particularly at gene level, to understand precise mechanism(s) involved in SA-mediated As-stress tolerance. <![CDATA[<b>Abundance of denitrifying genes and microbial community structure in volcanic soils</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300009&lng=pt&nrm=iso&tlng=pt Nitrous oxide (N2O) is a potent greenhouse gas produced during denitrification, a process that includes several genes coding enzymes responsible for nitrogen (N) forms transformations. In volcanic ash soils of southern Chile, fertilization had increased over the last 10 years with implications for N2O emissions. Despite this, little is still known about potential denitrification and the presence of denitrifying genes. In this study we report the abundance of denitrifying genes and a basal characterization of microbial communities in five volcanic ash soils with different levels of organic matter. The denitrifying genes determination showed that nosZI predominated over nirK and nirS in all soils suggesting a complete denitrification pathway, which would explain low N2O losses in such soils. Estimation of total microorganisms studies using 16S and 18S rRNA showed that in these soils bacteria (10(9)) was most abundant over archaea and fungi (10(7); p<0.05). Sequences of DNA obtained by denaturant gradient gel electrophoresis (DGGE) indicated that Firmicutes, Acidobacteria and Proteobacteria are the main bacterial classes represented in Andisoils (33, 28 and 23%, respectively) but with a lower diversity. More detailed studies about denitrifiers, gene-activity relationship and N2O emissions are required. <![CDATA[<b>Structural characterization of a compacted alfisol under different tillage systems</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300010&lng=pt&nrm=iso&tlng=pt Conservation tillage is a management system used to mitigate and rehabilitate the dryland areas of southern-central Chile in severely compacted soils. The objective of this study was to evaluate the soil physical properties in the root zone under an oat-wheat crop rotation after three years of the establishment of three tillage systems: conventional tillage (CT), zero tillage (ZT) and zero tillage with subsoiling (ZTS). Soil bulk density, porosity, water retention curve, stability of macro- and microaggregates, airflow at field capacity, rest coefficient, and number of roots were evaluated. The results showed that the soil had low water holding capacity in the profile due to the low water retention at the permanent wilting point (matric water potential lower than -1.500 kPa), associated with a high bulk density and clay content. The conservation tillage systems (ZT and ZTS), were similar in the parameters of fast drainage pores (FDP), aggregate stability index, airflow, and rest coefficient compared with CT. However, the volume of pores with diameters between 10-50 μm was higher in ZTS in a 24% and 13%, compared with ZT and CT, respectively. In addition, the root development increased significantly in ZTS. In conclusion, the physical condition of the compacted soil was improved by the zero tillage system with subsoiling, which promoted a better root system in the first horizons in highly compacted soils. <![CDATA[<b>Effect of micronutrients foliar application and biofertilizeres on essential oils of lemon balm</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300011&lng=pt&nrm=iso&tlng=pt In this work, the effects of two micronutrients (Mn2+, H2Bo3-) and macronutrients (PO4(3-) and NO3-) from biofertilizeres resources on growth (leaf dry/fresh weight, root dry/fresh weight, stem/root length, number of stem) and accumulation of essential oils in Lemon balm (Melissa officinalis L.) were investigated. The most of essential oils in two seasons were Caryophyllene oxide, E-Caryophyllene, Geranial, Geraniol, Chavicol and Neral that affected by the treatments. Of the two micronutrients, manganese, and in macronutrients NO3- were more effective in stimulating the accumulation of components. At 150 ppm of micronutrients by biofertilizeres, enhanced the production of citronellal, Chavicol. Although combination of H2Bo3-and Mn2+ at 300 ppm by macronutrients in some of essential oils like neral, caryophyllene oxide and 14-hydroxy-Z-caryophyllene were more produced than 150 ppm combinations but most of essential oils significantly increased in 150 ppm concentration of micronutrients with macronutrients. Exo-Isocitral, Chavicol, 14-hydroxy-Z-Caryophyllene and Germacrene D, were upper extracted in 150 ppm concentration of micronutrients but in many combinations this essential oil was no extracted in little concentration. <![CDATA[<b>The physical properties,</b> <b>lignin distribution, chemical composition of fibers and gas exchange rate of kenaf (<i>Hibiscus cannabinus</i> L.) varieties under prolonged water deficiency</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300012&lng=pt&nrm=iso&tlng=pt The fundamental characteristics and physical properties of kenaf (Hibiscus cannabinus L.) fibers cultivated and subjected to three different water frequencies in Universiti Putra Malaysia, were analyzed. For deep analysis, which includes micro-scale viewing for identification of kenaf cell wall structure, fibers were viewed in order to study the physical characteristics, anatomy, and lignin distribution. The chemical composition was determined considering Technical Association of Pulp and Paper Industry (TAPPI) methods. Water stress treatments were imposed on the plants four weeks after germination when they had attained more than four leaves: daily watering based on soil field capacity (100% ER; well watered), water stress imposition 1 month after seedling establishment completion (1 MAS) and water stress imposition at flowering stage (AFS). Each water treatment was replicated three times in a randomized complete block design (RCBD) in split plot arrangement with water treatments as the main plots and the varieties as the sub-plots; irrigation system was applied for the purpose. Different water treatments and different varieties at the end of experimental period had significant impact on fiber dimensions and physiological attributes. Fiber quality attributes, gas exchange rate and Growth parameters were affected in negative way when all varieties had been subjected to water stress regardless of time of stress imposition. <![CDATA[<b>Effects of application of exogenous NO on the physiological characteristics of perennial ryegrass grown in Cd-contaminated soil</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300013&lng=pt&nrm=iso&tlng=pt A pot experiment was conducted to study the effects of sodium nitroprusside (SNP, a nitric oxide [NO] donor) on cadmium (Cd) toxicity in ryegrass plants. In the present study, ryegrass plants subjected to Cd toxicity were treated with different concentrations of SNP (50, 100, 300 and 500 µM), SNP solution was poured into Cd-contaminated soil every seven days. Cd treatment inhibited the plants growth and the absorption of micronutrients, increased accumulation of Cd in both shoots and roots. In Cd-treated plants, the activities of antioxidant enzymes and the contents of proline, soluble protein and ascorbic acid (AsA) decreased dramatically, whereas the accumulation of superoxide anion (O2.-), hydrogen peroxide (H2O2) and malondialdehyde (MDA) increased significantly. Addition of SNP significantly decreased O2.-, H2O2 and MDA accumulation in both shoots and roots of Cd-stressed plants, decreased the transport of Cd from roots to shoots, alleviated the inhibition of Ca, Fe, Mg and Zn absorption induced by Cd and promoted the plant growth. In SNP-treated plants, the chlorophyll content, the contents of proline, soluble protein and ascorbic acid, and the activities of superoxide dismutase, peroxidase and catalase increased considerably. Addition of 300 µM SNP had the most significant alleviating effect against Cd toxicity while the addition of 500 µM SNP had no significant effect with Cd treatment. Based on these results, we concluded that the optimal concentrations of exogenous SNP could alleviate Cd induced stress and promote ryegrass plant growth. <![CDATA[<strong>Dairy slurry application to grasslands and groundwater quality in a volcanic soil</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300014&lng=pt&nrm=iso&tlng=pt Research in volcanic-ash soils has shown that they largely capture the dairy slurry following application to land; however, their hydrological properties would favor nutrient leaching. Our objective was to evaluate the contribution of biogeochemical and hydrological controls on the pollution of groundwater by cattle slurry applied to a permanent grassland growing on a volcanic soil. We sampled groundwater chemistry since 10 months before the fertilization (three samplings), and 16 months after, with samplings 1-2 months after the fertigation. Following fertilization, ammonium, exchangeable potassium, and magnesium soil concentrations increased in the fertilized plots compared to the control plots. In contrast, no effect of slurry on groundwater quality was detected, with the exception of dissolved organic nitrogen, a main component of dairy slurry that increased in the groundwater below the fertilized plots. Despite the fact that biogeochemical controls predominate, hydrological aspects would be important when rainfall is high, evapotranspiration is low, groundwater table level is high, and water movement in the saturated zone increases. We concluded that the application of slurry to pastures under rates comparable to a high fertilization in the short term, does not generally impact the groundwater quality in volcanic ash-derived soils. <![CDATA[<b><i>Phragmites australis</i></b> <b>and <i>Schoenoplectus californicus</i> in constructed wetlands</b>: <b>Development and nutrient uptake</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300015&lng=pt&nrm=iso&tlng=pt The goal of this work was to evaluate the development and nutrient uptake by Phragmites australis (Phr) and Schoenoplectus californicus (Sch) in horizontal subsurface flow constructed wetlands (HSSF) designed for wastewater treatment. Four HSSF systems with a surface area of 4.5 m² were planted with Phr and Sch. Wastewater was fed for 3 years at 1.6 to 4.8 g N m-2 d-1 and 0.2 to 0.6 g P m-2 d-1. Nutrients (total nitrogen-TN and total phosphorus-TP), organic matter (chemical oxygen demand-COD) and solids (total suspended solids-TSS) were evaluated. Nitrogen and phosphorus uptake were 7.52 g N m-2 and 0.83 g P m-2 for HSSF-Sch and 11.39 g N m-2 and 0.23 g P m-2 for HSSF-Phr. Showing a development of biomass of HSSF-Sch and HSSF-Phr were 1782 g DW m-2 and 385 g DW m-2, respectively. Under these conditions, the removal efficiencies were 55-63% of COD and 88-92% of TSS for HSSF-Phr and 46-66% of COD and 83-91% of TSS for HSSF-Sch. TN removal was 23-24% for HSSF-Phr and 18-23% for HSSF-Sch. At the same time, removal for TP was -1 to 4% for HSSF-Phr and for HSSF-Sch was 9-13%. <![CDATA[<b>Soil ecophysiological and microbiological indices of soil health</b>: <b>a study of coal mining site in Sonbhadra, Uttar Pradesh</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300016&lng=pt&nrm=iso&tlng=pt The present study involves the discovery of quality of soils associated with dump mines and native forest encompassing the Kakari mine, a coal mining site in Sonbhadra, to distinguish the effect of coal mining on associated soil ecosystem. Soil ecophysiological indicator of the site was analyzed in terms of floral diversity by method of quadrat analysis, which revealed that dumps were devoid of any floral community whereas the natural forest around the mines was enriched with a number of plant species. Importance value index (IVI) was calculated and with respect to their IVI index the tree species viz., Acacia mangium (23.17, 24.48 & 26.81) and Acacia catechu (20.34, 22.10 & 25.36) were found to be the most dominant species. Soil enzymatic and physico-chemical analysis were analyzed by standard method and the result emphasized that dump soils possess poor enzymatic activity and acidic pH due to the decomposition of waste material in dumps which eventually affects the microbial diversity of soil and its fertility. The plant growth promotion (PGP) and stress tolerance characteristics of bacterial isolates were further examined so that the potential isolates will be utilized further to reclaim and remediate soil property of degraded soils. The promising isolates were characterized by BIOLOG identification system and isolate NU36 and NU25 showed greatest similarity with Pseudomonas sp. and Acinetobacter sp. respectively. Based on the potential to produce plant growth promoting substances and withstand in stressed environment the most promising isolates will be used to remediate soil and reclaim soil characteristics. <![CDATA[<b>Decomposition, N contribution and soil organic matter balances of crop residues and vermicompost in maize-based cropping systems in southwest Mexico</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300017&lng=pt&nrm=iso&tlng=pt Soil fertility depletion is one of the main concerns of the farmers in the Costa Chica, Mexico. The current crop management exacerbates nutrient cycling unbalances and threatens the sustainability of the common maize production systems. It is necessary to supply the soil with organic sources. Field experiments were established in farmers’ fields to estimate the decomposition rate and N release of organic materials: aboveground and belowground plant residues, and vermicompost. Decomposition was monitored using the litterbag method, and decomposition patterns were fitted by means of a dynamic mono-component mineralization model. To calculate the effects of crop residues retention and vermicompost on OM balance, five scenarios were evaluated with farm DESIGN model. The decomposition rate was greater during the first 4 months. After that period the remaining dry matter proportion of aboveground residues varied between 45 and 67%. In case of root residues, the dry weight loss ranged between 20 and 47% after the first month. For both types of residues, N released within the first month was 37%, on average. At the end of the sampling period 9 months, the remaining dry matter proportion of aboveground and belowground residues ranged from 30 to 55%, whereas more than 80% of their total N was released. After 6.5 months only 35% of the vermicompost mass was decomposed, but about 65% of its N was mineralized. Besides, around 70% of the vermicompost N was released during the first 30 days. In fields with vermicompost maize was responsible for 70% of total N uptake, on average. The N balance was 93% higher than maize fields without vermicompost. In scenario with 30% of crop residue retention along with vermicompost, OM balance was 86% higher than under current management. Vermicompost can be regarded as an attractive amendment for both crop N supply and soil organic matter build-up. <![CDATA[<b>Land use and soil development in southern Chile</b>: <b>Effects on physical properties</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300018&lng=pt&nrm=iso&tlng=pt Different physical properties of volcanic ash soils were investigated along a transect of 120 km from the western slope of the Central Cordilleras (40°20'S, 72°06'W) to the eastern slope of the Costal Cordillera (39°39'S, 73°11'W) in southern Chile with respect to the degree of soil development (Arenosol versus Andosol stage; Arenosol: young volcanic ash soil, free of clay, tephric properties, Andosol: older volcanic soil, clayey). The Andosols show a higher total pore volume and a higher field capacity, especially due to an increase in fine pores, than the Arenosols. Furthermore, the precompression stress (Pc) as a parameter for the mechanical soil strength is higher for Andosols despite of a lower bulk density. A land use (cropland, meadow, forest) dependent variation of the investigated parameters was less distinct for Andosols. A reduction of macropores and saturated hydraulic conductivity (ks) due to agriculture could be determined in the field, but in general the values are still on a high level with ks-values &gt;100 cm d-1. However, at higher stresses using an oedometer test the ks-values of the Andosols are highly negatively affected with values <10 cm d-1. Aggregation is of major importance for soil stability of Andosols, whereas a homogenization of soil structure will lead to a distinct decrease of Pc of approx. 50%. <![CDATA[<b>Soil chemistry and nutrient concentrations in perennial ryegrass as influenced by gypsum and carbon amendments</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300019&lng=pt&nrm=iso&tlng=pt Plant growth is affected by soil properties that can be improved through addition of amendments and other management practices. Use of gypsum as a soil amendment for improving agricultural yields, and soil and water quality is increasing, but knowledge is lacking on how it affects the soil’s chemical properties and plant growth. This greenhouse study measured changes in soil chemistry, growth and nutrient uptake response of ryegrass (Lolium perenne) grown in two contrasting soil types amended with crop residues, glucose, and gypsum. The soil chemical properties, biomass yield, and elemental composition of ryegrass shoots and roots were evaluated. Residue addition significantly increased total soil N and pH, and glucose significantly lowered soil pH. Gypsum significantly increased pH in the 25-40 cm layer only and exchangeable Ca in all layers, and decreased Bray P-1 in the surface layer by 40%. No significant effects were observed in above-ground ryegrass biomass with addition of inputs. Compared to the untreated soil, gypsum increased Ca and S uptake by 50 and 259%, respectively, in the last harvest and Ca, S and Mo in roots by 77, 175, and 18%. Addition of residues and gypsum improved soil chemical properties, nutrient availability, and uptake, but not ryegrass yield. <![CDATA[<strong>Assessment of plant growth promoting activities and abiotic stress tolerance of <i>Azotobacter chroococcum</i> strains for a potential use in sustainable agriculture</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162016000300020&lng=pt&nrm=iso&tlng=pt This study aimed to select and characterize bacterial strains with multiple plant growth promotion properties able to tolerate drought and salinity stress in order to improve plant growth performance under abiotic stresses. Plant growth promoting activities were evaluated in 106 bacterial strains isolated by soil, compost, lignocellulosic biomasses and food matrices. Two strains A. chroococcum 67B and 76A were selected for their multiple plant growth promotion activities (N2-fixing activity, synthesis of siderophores and indole-3-acetic acid) as well as antimicrobial activity against Sclerotinia minor. Moreover, the selected strains were tested for their tolerance to drought and salinity stress in in vitro experiments evaluating their growth, production of SOD, CAT, proline and ACC deaminase. The two Azotobacter chroococcum strains exhibited high tolerance to salt and drought stresses and could alleviate the negative effects exerted by abiotic stress on tomato plants. Overall results showed that the strains Azotobacter chroococcum 67B and Azotobacter chroococcum 76A could be interesting candidates to be employed as bio-effector in sustainable agricultural systems also under stressful conditions leading to improved economic and environmental benefits.