Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> https://scielo.conicyt.cl/rss.php?pid=0718-951620130003&lang=pt vol. 13 num. 3 lang. pt <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[<b>Effect of fulvic acid on the phosphorus availability in acid soil</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300001&lng=pt&nrm=iso&tlng=pt The incubation experiment was conducted to evaluate the influence of fulvic acid (FA) on phosphorus (P) movement and transformation in acid soil. FA at the rate of 0, 0.1, 0.2, 0.3 g and in combination with 0.19 g KH2PO4 was sprinkled uniformly on the surface of the filter paper on the soil cylinder for 21 days incubation, respectively. The result showed that the pH of soil treated with FA increased from the original value of 5.83 to the highest value of 6.27 in the surface soil layer after 21 days incubation. Due to the application of FA, exchangeable Al concentration evidently decreased in comparison to the only P treatment, which in turn significantly increased available P concentration. FA also increased the movement length of P that reached 4.5, 5.5 and 6.5 cm depth for treatments reinforced with 0.1, 0.2 and 0.3 g FA per column, respectively. As FA was added into soil, microbial population, organic matter content and cation exchange capacity (CEC) all clearly elevated. It is suggested that P fertilizer and FA are fertilized together may be considered as an optimum choice for the improvement of P availability and soil physicochemical conditions. <![CDATA[<b>Exogenous indole-3-acetic acid could reduce the accumulation of aluminum in root apex of wheat <i>(Triticum aestivum</i> L.) under Al stress</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300002&lng=pt&nrm=iso&tlng=pt Indole-3-acetic acid (IAA) is hormones in higher plants and participates in plant growth regulation and stress resistance including Al stress. The reduction of root apex aluminum (Al) content by exogenous IAA treatment was hypothesized to be effective in alleviating the adverse effect of high Al concentration in wheat root growth. To investigate the role of IAA in lowering root apex Al content, Al-tolerant wheat (ET8) was studied in Al solution (50 µM), co-treated with IAA (25 µM) and anion channel inhibitors (5 µM NIF or A9C) or IAA transport inhibitors (5 µM TIBA or NPA) under acidic condition for 24 h. Treatments were as fellows: control (0.5 µM CaCl2), Al (50 µM), Al (50 µM) + IAA (25 µM), Al (50 µM) + IAA (25 µM) + NIF (or A9C, 5 mM), Al (50 µM) + NPA (or TIBA, 5 µM). Al content in root apex, rhizosphere pH and PM H+-ATPase activity were studied. The results showed that co-treatment with IAA reduced root apex Al content by 42% compared to Al treatment. Anion channel inhibitors enhanced the accumulation of Al in root apex by 27% (or 32%) (NIF or A9C), while addition of IAA neutralized its promoting effect. The co-treatment with IAA increased rhizosphere pH by alleviating the decrease of plasma membrane H+-ATPase activity, while IAA transport inhibitors (NPA or TIBA) suppressed the elevation of rhizosphere pH. The current results suggested that IAA could be effective in alleviating Al toxicity through reducing Al accumulation in wheat root apex. <![CDATA[<b>Use efficiency and residual effect of <sup>15</sup>N-labelled ryegrass green manure over a 9-year field micro-plot experiment</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300003&lng=pt&nrm=iso&tlng=pt A 9-year field micro-plot experiment was conducted to investigate the use efficiency, residual effect, and fate of 15N-labelled ryegrass green manure in soil-crop system, so as to offer useful information for reasonable application of green manures on meadow burozem. Results showed that high application rate (600g per plot) of 15N-labelled ryegrass green manure resulted in reduction of percent recovery (PR)15Nplant and PR15Nsoil by 25.0% and 12.8%, respectively, and elevation of percent loss (PL)15N by 31.2%, as compared with low application rate. The 15N utilization and loss could be divided into three phases, i.e., high uptake and fast loss in the first and second growth seasons, low uptake and slow loss in the following four growth seasons, and little change in the last three growth seasons. This suggested that the green manure N had a long residual effect but its loss was faster at early phase, and thus, rational application of green manure was of considerable importance to reduce its N loss while improve its N use efficiency. <![CDATA[<b>Yield mapping of arabic coffee and their relationship with plant nutritional status</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300004&lng=pt&nrm=iso&tlng=pt The aim of this study was to model the spatial variability of the nutritional status of arabic coffee using leaf macro and micronutrient contents and relate it to drop in bean yield, bark percentage and crop yield. The experiment was conducted in a plantation of arabic coffee variety Catuaí located in the Zona da Mata of Minas Gerais State. Leaf nutrient contents, cherry coffee production, drop in bean yield, yield of benefited coffee and bark percentage were determined. Data were analyzed using classical statistical methods to find the relationship between nutrients and yield variables and then examined by geostatistical analysis. The yield variables and leaf nutrients that were found related showed spatial dependence without random distribution. Nutritional imbalance was detected in the studied coffee crop expressed by the deficiency or excess of some nutrients in the plant tissue. Ca provided the smallest drop in bean yield while the leaf contents of B and Zn had an opposite effect on the production and yield of coffee. <![CDATA[<b>Soil greenhouse gas fluxes and net global warming potential from intensively cultivated vegetable fields in southwestern China</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300005&lng=pt&nrm=iso&tlng=pt Vegetable fields in China are characterized with intensive fertilization and cultivation, and their net effect on the global warming deserves attention. Greenhouse gas fluxes were thus measured, using a static closed chamber method, over approximately 18 months in two typical subtropical vegetable fields with different soil types and contrasting soil properties. Five consecutive crops were planted in one field and four in the other. Intensive fertilization consistently stimulated soil N2O emission, while imposed complicated impact on soil respiration with CO2 emission enhanced in one field and suppressed in the other field. The fertilizer-induced N2O emission factors (EFs) varied with individual crop phases and averaged 1.4 to 3.1% across the whole sampling period for different fields. The interaction of soil temperature and moisture could explain about 58% of the seasonal variation in the EFs. All the soils under different vegetable cropping systems were net sources of atmospheric radiative forcing and the net global warming potential over the entire study period ranged from 1,786 to 3,569 g CO2 equivalence m-2 for fertilized soils with net CO2 emission contributing 53 to 67% and N2O emission occupying the remaining 33 to 47%. <![CDATA[<b>Effects of the nitrification inhibitor DMPP on soil bacterial community in a Cambisol in northeast China</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300006&lng=pt&nrm=iso&tlng=pt A long-term experimental site was built to study effects of the nitrification inhibitor 3, 4-dimethylpyrazole phosphate (DMPP) on a bacterial population's diversity and activity in a Cambisol in northern China. Treatments included no fertilization (CK), application of urea alone (U), and application of urea plus DMPP (UD). The annual application rate for the urea was 180 kg N ha-1, and that of the DMPP was 1.8 kg ha-1. The diversity and composition of the overall soil bacterial community were analyzed using pyrosequencing, and the abundances of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were analyzed using a real-time polymerase chain reaction (RT-PCR) assay. The dominant phyla were Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Gemmatimonadetes, Chloroflexi, Firmicutes, and Planctomycetes in all of the samples. However, compared with treatment U, the relative abundance and identities of the dominant phyla that were increased in treatment UD were more similar to those of the CK treatment. DMPP significantly reduced the targeted ammonia oxidizing bacterial abundance, and the soil potential nitrification rate had a significant positive correlation with the amoA gene copy number of the AOB (r=0.685, n=9, p<0.05) but not of the AOA. The results suggested that long-term application of DMPP to this agricultural soil was relatively beneficial for both urea application and soil bacterial ecosystem reversion. <![CDATA[<b>Plant and soil characteristics affected by biofertilizers from rocks and organic matter inoculated with diazotrophic bacteria and fungi that produce chitosan</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300007&lng=pt&nrm=iso&tlng=pt The aim of this study was to evaluate the effectiveness of a mixed biofertilizer with phosphate and potash rocks (PK biofertilizer) combined with an earthworm compound inoculated with free living diazotrophic bacteria and Cunninghamella elegans, fungi that produces chitosan, on cowpea nodulation, biomass yield and nutrient uptake. The effects of some chemical attributes from an acidic soil of the Brazilian Northeast were also studied. The treatments were as follows: a) biofertilizer enriched in N by free living diazotrophic bacteria(NPKB), applying crustaceous chitosan (ChCru) at a rate 2 mg mL-1.; b) NPKB and ChCru at a rate 4 mg mL-1.; c) NPKB and ChCru at a rate 6 mg mL-1.; d) NPKB and fungi chitosan (ChFu, 2 mg mL-1); e) NPKB+C. elegans (NPKP); f) NPKB without chitosan; g) mineral fertilizers (NPKF); and h) control without NPK fertilizer and chitosan. Biofertilizer treatments increased cowpea nodules biomass, shoot biomass, and total N, P, and K in the shoots. The largest increase was obtained with ChCru, and the highest rate was obtained with NPKP. Furthermore, biofertilizers reduced soil pH and increased the total N and available P and K. These results reveal the potential of rock biofertilizer mixed with earthworm compound inoculated with free living diazotrophic bacteria and C. elegans (fungi chitosan) for plant production and nutrient uptake. The biofertilizer may be an alternative for NPK fertilization that slows the release of nutrients, favoring longterm soil fertility. <![CDATA[<b>Root-exuded malic acid versus chlorophyll fluorescence parameters in four plant species under different phosphorus levels</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300008&lng=pt&nrm=iso&tlng=pt The amount of root-exuded malic acid and chlorophyll fluorescence parameters (the minimum chlorophyll fluorescence; the maximum quantum yield of photosystem II) in four plant species (Broussonetia papyrifera, Morus alba, Orychophragmus violaceus and Brassica napus) at different phosphorus levels was studied. A linear equation presents the minimum chlorophyll fluorescence (Fo) or the maximum quantum yield of photosystem II (Fv/Fm) and the amount of root-exuded malic acid. Broussonetia papyrifera and Orychophragmus violaceus easily adapted to a low-phosphorus environment. A low-cost method was used for assessing plant adaptability to a low-phosphorus environment when no chlorophyll fluorescence instrument was available. <![CDATA[<b>The effects of phosphite on strawberry yield and fruit quality</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300009&lng=pt&nrm=iso&tlng=pt Phosphite (H2PO3-; Phi) has been shown to increase fruit quality and activate plant defense mechanisms in plants when provided in a nutrient state with sufficient phosphorous. In this study, five solutions containing different percentages of Phi (0, 20, 30, 40 and 50%) in Steiner's solution were evaluated during the flowering and fructification stages; the Steiner' s nutrient solution was kept al 50% during the flowering stage and at 75% from the beginning of the fructification stage on. The objective was to determine the effects of phosphite on total P concentration in leaves, yield, pH, electrical conductivity (EC), anthocyanin concentration, and fruit size of strawberries (cv. Festival). The experiments were performed in a tunnel-type greenhouse using drip irrigation and volcanic rock (volcanic gravel) as substrate. In the fruit development phase, the concentration of P in the leaves was proportional to the level of Phi used. Although no significant differences were observed when compared to the control, the addition of 20% Phi slightly improved yield and fruit size. The highest pH, EC and anthocyanin concentration were identified in the fruit of plants treated with 30% Phi. Our findings suggest that supplying Phi at 30% or less in the nutrient solution does not significantly affect yield but does affect fruit quality and activates plant defense mechanisms by producing a higher concentration of anthocyanins. <![CDATA[<b>Conservation tillage and water availability for wheat in the dryland of central Chile</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300010&lng=pt&nrm=iso&tlng=pt The dryland areas of Central Chile are associated to Mediterranean climate. Under these conditions, water availability during crop growth is a crucial factor for crop productivity. Conservation tillage systems play an important role in this area, increasing soil water availability; however, crop yield responses can be variable. Soil management should be aimed at reducing water loss and promoting water use by crops. The aim of this review is to analyze and discuss the factors affecting water availability in the Mediterranean drylands of Central Chile, as well as to study the effect of tillage systems on the water use efficiency of wheat. <![CDATA[<b>Isolation and characterization of indole acetic acid (IAA) producing bacteria from rhizospheric soil and its effect on plant growth</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300011&lng=pt&nrm=iso&tlng=pt Indole acetic acid (IAA) production is a major property of rhizosphere bacteria that stimulate and facilitate plant growth. The present work deals with isolation, characterization and identification of indole acetic acid producing bacteria from the rhizospheric soil. Out of ten Indole acetic acid producing isolates, five were selected as efficient producers. Optimization of indole acetic acid production was carried out at different cultural conditions of pH and temperature with varying media components such as carbon and nitrogen source, tryptophan concentration. Partial purification of IAA was done and purity was confirmed with Thin layer chromatography. Subsequently, effect on plant growth was tested by pot assay. In conclusion the study suggests the IAA producing bacteria as efficient biofertilizer inoculants to promote plant growth. <![CDATA[<b>Soil and foliar fertilization affects mineral contents in <i>Vitis vinifera</i> L. cv. 'rebula' leaves</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300012&lng=pt&nrm=iso&tlng=pt Grapevine nutrient oversupply as well as shortage can both result in unbalanced vine growth and poor grape production. Mineral fertilization is a powerful tool also in viticulture in order to increase yields and improve grape quality. The trial carried out in Slovenian winegrowing region investigated the effects of basic fertilization coupled with soil or foliar applications of fertilizers containing Mg and Fe on the concentration of K, Mg, Fe and Zn in the grapevines leaves at berry set and veraison. The results obtained in a 2-years study (2008-09) with seven different fertilization treatments (along with control) showed that fertilization with K decreased Mg uptake almost on a half comparing to untreated vines, resulting in basal leaves chlorosis. High K/Mg ratio, determining low Mg uptake, was not lowered in our trial neither by foliar spraying nor by fertirigation with MgSO4 solution. On the other hand, Mg application in addition to Fe supply had same effect on soil Zn uptake and its accumulation in the leaf petioles. Moreover, foliar Fe fertilization enhanced Fe levels in blades at berry set and to a lesser extent also at veraison. <![CDATA[<b>Zinc desorption kinetics in wheat <i>(Triticum Aestivum</i> L.) rhizosphere in some sewage sludge amended soils</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300013&lng=pt&nrm=iso&tlng=pt The objectives of this study were to determine Zn desorption characteristics and the correlation of these parameters with Zn extracted by DTPA-TEA method in bulk and rhizosphere amended soils with sewage sludge under greenhouse conditions by using a rhizobox. For amended soils 10 g of sewage sludge was added to 1 kg of 10 soil samples. The kinetics of Zn desorption in bulk and rhizosphere was determined by successive extraction with DTPA-TEA in a period of 1 to 504 h at 25±1 0C. The results showed that Zn extracted using successive extraction in the rhizosphere were significantly (p<0.01) higher than in the bulk amended soils. The best model for describing extraction data for bulk and rhizosphere soils was the power function equation. The results indicated that Zn desorption rate in the wheat rhizosphere soils more than bulk soils. The results showed that significant correlation (p<0.05) between Zn desorption characteristics and DTPA-TEA-Zn were found in the bulk and rhizosphere soils. The results of this research revealed that Zn desorption characteristics that are help to estimate the Zn supplying power of soils in the wheat rhizosphere, are quite different than bulk amended with sewage sludge. <![CDATA[<b>Effect of arginine pre-treatment on nickel accumulation and alleviation of the oxidative stress in <i>Hyoscyamus niger</i></b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300014&lng=pt&nrm=iso&tlng=pt Nickel is essential for many plant species to complete their life cycle but higher concentrations of this metal are toxic and may severely interfere with many physiological and biochemical processes of plants. In recent researches, either sodium nitroprusside (as nitric oxide donor) or exogenous polyamines were used to counteract the effect of heavy metal stress. In this research hyoscyamus plants were pre-treated with 10 and 20 µM Arg (as a precursor of NO or polyamines) and then plants were treated with 50 and 100 µM Ni. Elevated hydrogen peroxide content and lipoxygenase (LOX) activity showed that Ni induced oxidative damages. Antioxidant enzyme activity also increased in those plants which were under Ni stress. In plants, which were pretreated with Arg, the concentration of Ni increased in shoot, while the H2O2 content and the activity of LOX, catalase (CAT), guiacol peroxidase (GPX) and ascorbate peroxidase (APX) enzymes decreased. It is shown for the first time that pre-treatment of hyoscyamus plant with Arg increased plant capability to accumulate Ni in its aboveground organs by 1.5-2 times and reduced its toxic effects indicated by measurement of oxidative parameters. It might be true because Arginine induced alleviation of Ni toxicity and accelerated transport by chelating of Ni in plants directly or through production of polyamines. <![CDATA[<b>Physical properties of a fine textured haplocambid after three years of organic matter amendments management</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300015&lng=pt&nrm=iso&tlng=pt In Copiapó Valley, the 3th Region of Chile, a three-year study (2007-2009) was conducted to evaluate the effect of organic amendments and cover crops on soil physical properties (Typic Haplocambid) in a table grape (Vitis vinifera) orchard. Four treatments were established during three seasons: control without organic amendments (T1), broad bean-corn-rape rotation (T2), goat manure addition (15 t ha-1) (T3) and corn-broad bean-barley rotation (T4). Soils measurements, bulk density, pore size distribution, aggregate stability, water repellence and air conductivity were conducted on soil samples collected at three soil depths (0-10, 10-30 and 30-50 cm). Saturated hydraulic conductivity and mechanical strength were also evaluated. On grape plant measurements, root development, pruning weight and harvested grape production were evaluated. Soil bulk density was reduced with goat manure addition in comparison with any other treatment, which resulted in lower mechanical strength in the top soils. None of the treatments had negative effects on water repellency. The crop treatments enhanced the coarse porosity throughout the soil profile, improving the continuity of porous system with their root development and inducing high air conductivity. Other hand, the control soil and manure application showed a pore discontinuity in a pre-existing plow pan. Aggregate stability and saturated hydraulic conductivity were greater in goat manure application, but the treatments which included crop rotation did not show significant differences compared with the control. Because of the short duration of the study, it is assumed that the soil improvements were not detected as expected in grape production yet. <![CDATA[<b>Agronomic properties and nutritional status of plum trees <i>(Prunus domestica</i> L.) influenced by different cultivars</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300016&lng=pt&nrm=iso&tlng=pt The tree growth, fruit weight and leaf mineral status of ten plum cultivars grafted on rootstock of autochthonous plum 'Belosljiva' under high density planting system (HDP) on acidic soil was investigated in the fifth and sixth leaf. Results indicated that tree vigour, fruit weight and productivity significantly depend on the cultivar. 'Čačanska Najbolja' had the most vigorous trees, while 'Čačanska Lepotica' had the smallest. The fruit weight was the highest in 'Čačanska Rana', and the lowest in 'd'Agen'. 'Stanley' was the most productive cultivar in 2006 and 'Čačanska Rodna' in 2007. Yield efficiency was the highest in 'Čačanska Lepotica' and the lowest in 'Ruth Gerstetter', 'Čačanska Rana', 'Čačanska Najbolja' and 'Opal', respectively. Significant differences were observed among cultivars for leaf major nutrient (N, P, K, Ca, Mg) levels at 120 DAFB. Larger imbalance of leaf major elements was observed in 'd'Agen', whereas good balance was found in 'Violeta'. <![CDATA[<b><i>Elymus dahuricus</i> H<sup>+</sup>-PPase <i>EdVP1</i> enhances potassium uptake and utilization of wheat through the development of root system</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300017&lng=pt&nrm=iso&tlng=pt We investigated the differences of K acquisition and utilization, morphological and physiological characteristics of roots and grain yield between Elymus dahuricus H+-PPase (EdVP1) transgenic wheat and wild type wheat under low K stress. The results showed that, the grain yield and K economic utilization index (KUI-E) in wild type wheat were only 61.14% and 50.20% of those in EdVP1 transgenic wheat. EdVP1 increased the free IAA accumulations in roots, which may play a key role in the development of root system. The total root length, total root surface area, root tips and total root volume in transgenic wheat were 2.26, 2.23, 2.34 and 2.00 times as high as those in wild type wheat, respectively. Excretion H+ and cation exchange capacity (CEC) of roots, which were enhanced in transgenic wheat, were positively correlated with K content.The exudate of organic acid intransgenic wheat was 2.22 times as high as that in wild type wheat, leading to the strong K activation of transgenic wheat. Therefore, we assume that well-developed rootsystem containing prosperous root morphology, high excretion H+ and CEC of roots and strong excretion ability of organic acids improved K acquisition and utilization efficiency in EdVP1 transgenic wheat. <![CDATA[<b>The development and suppressive activity of soil microbial communities under compost amendment</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300018&lng=pt&nrm=iso&tlng=pt Soil is a highly complex system in which bacteria play a dominant role. Soil microorganism biodiversity is extremely important for sustaining the nutrient cycles of soil ecosystems. The diversity of soil bacterial and fungal communities can be influenced by agricultural management. The use of amendments, such as the incorporation of compost into the soil, strongly affects soil microbial communities directly or indirectly. The use of compost can be an important tool to control soil-borne pathogens. Certain groups of microorganisms (bacteria and fungi) present in compost produce metabolites, such as siderophores and antibiotics, with specific suppressive activity against soil-borne pathogens: among these compost bacteria, species of Pseudomonas and Bacillus are very important. In this study, we investigated the effects of increasing doses of compost on the density of several cultivable soil microbial groups in an agricultural system of Southern Italy. The number of total bacteria, total fungi, siderophore-producing bacteria (principally Pseudomonas spp.) and spore-forming bacteria (principally Bacillus spp.) was evaluated over a period of five months. Moreover, we analyzed the ability of spore-forming bacteria isolated from soil and compost to inhibit, in vitro, five soil-borne phytopathogenic fungi (Rhizoctonia solani, Fusarium oxysporum, Sclerotinia minor, Fusarium solani, Pyrenochaeta lycopersici). The number of total bacteria and siderophore-producing bacteria was greater in the soil treated with compost than in soils treated with mineral fertilization or not manured, with an increase related to the dose of compost applied. Moreover, the compost used in this study produced a substantial increase in the number of spore-forming bacteria in the soil. Approximately 80% of these bacteria were able to inhibit the soil-borne phytopathogenic fungi Rhizoctonia solani, Fusarium oxysporum, Sclerotinia minor, Fusarium solani and Pyrenochaeta lycopersici. These results show that compost from the organic fraction of municipal solid wastes furnishes a high number of spore-forming bacteria exhibiting antibiotic activity against phytopathogenic fungi. The application of compost can change the composition of the soil microbial community, modifying the relationships among microorganisms, both competitive and/or antagonistic, producing a decrease in the activity of plant pathogens. These results were in agreement with the decrease in the symptoms of disease on tomato plants cultivated in the soils treated in this study. <![CDATA[<b>Effect of poly (</b><em><b>γ</b></em><b>-glutamic acid) on wheat productivity, nitrogen use efficiency and soil microbes</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300019&lng=pt&nrm=iso&tlng=pt Recently, with numerous environmental problems being caused by chemical fertilizer overuse, agricultural practices are shifting toward the development of environmentally friendly N fertilizers. In this study, pot and field experiments were simultaneously conducted to investigate the effect of poly(y-glutamic acid) (γ-PGA) on the yield, N use efficiency, and soil microenvironment of wheat. Our study demonstrates a statistically significant increase in winter wheat, number of tillers, seed number per spike, yield, soil microbial biomass N (SMBN), and soil enzymes after γ-PGA application. The highest grain yield of 7435.69 ± 55.91 kg ha-1 was obtained after γ-PGA application in the field experiment, which was 7.17% higher than the urea control. The N recovery efficiency increased by 11.81%-14.00% and 11.30%-11.38% after the application of γ-PGA in pot and field experiments, respectively. More mineral nitrogen in soil was immobilized by the microbes after γ-PGA application at the early growth stage of wheat. The immobilized nitrogen was gradually released at the late growth stage. The results demonstrate that γ-PGA can be used as a fertilizer synergist. <![CDATA[<b>Hydraulic conductivity variation in chilean volcanic soils due to wheeling and management</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162013000300020&lng=pt&nrm=iso&tlng=pt To describe the effect of wheeling on saturated hydraulic conductivity (ks), undisturbed soil samples from an Andisol were collected at three depths In Chilean soil classification system Andisols are defined as Malihue at the 2 sites minor and mayor mechanical stresses were applied repeatedly and the hydraulic properties determined for all depths. The saturated hydraulic conductivity Ks was reduced due to wheeling but the magnitude depended on the speed and load during wheeling. In addition, also the pore size distribution was reduced both in total but also in size classes. Smaller values of Ks were observed in Site 2 where low speed and low tire inflation pressure were applied, while the traffic induces a reduction of the pore associated to a reduced functionality of the porous system. To assess these qualitative changes and soil behaviour, measurements like hydraulic conductivity (ks) are a good tool to describe the physical quality of a soil.