Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> http://www.scielo.cl/rss.php?pid=0718-951620170001&lang=es vol. 17 num. 1 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>Residue addition frequency influences respiration, microbial biomass and nutrient availability in soil amended with high and low C/N residue</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100001&lng=es&nrm=iso&tlng=es In previous studies, we showed that the C/N ratio of the first residue added influences soil respiration, microbial biomass and nutrient availability after the second residue addition which we refer to as legacy effect. The aim of the study was to investigate the effect of residue addition frequency on microbial activity and nutrient availability, and the legacy effect. In Part A, the effect of high C/N residue (H) addition frequency in the first 16 days (d) was studied by adding H to soil once (d0), twice (d0, 8) or four times (d0, 4, 8, 12) followed by 10 g kg-1 low C/N residue (L) on day 16. The influence of L addition rate was assessed in Part B by adding H once on day 0 followed by L added once (d16), twice (d16, 24) or four times (d16, 20, 24, 24, 28). Cumulative respiration, microbial biomass C, N and P, N and P availability from d0 to d15 were higher with L than H. Particularly with L, cumulative respiration, microbial biomass and nutrient availability compared to single addition were lower on d7 with residue added twice or four times, but higher on d15. In Part A, H added twice or four times from d0 to d15 compared to a single H addition followed by a single L addition on d16 increased cumulative respiration, microbial nutrient uptake and reduced N and P availability on d23, but had no effect on d32. In Part B, frequent L addition after d16 enhanced microbial nutrient uptake on d23 but reducing nutrient availability compared to single L addition. It can be concluded that residue addition frequency strongly influences soil respiration, microbial biomass and nutrient availability after addition of low C/N residue. <![CDATA[<b>Contribution of inoculation with arbuscular mycorrhizal fungi to the bioremediation of a copper contaminated soil using <i>Oenothera picensis</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100002&lng=es&nrm=iso&tlng=es The Bradford-reactive soil protein (BRSP) fraction includes glomalin, a glycoprotein produced by arbuscular mycorrhizal (AM) fungi able to bind some metals, such as copper (Cu), which could promote the bioremediation of Cu-polluted soils. This study aimed to analyze the Cu-binding capacity of BRSP in Oenothera picensis that was inoculated or not inoculated with AM fungi. O. picensis plants were established in a Cu contaminated sterilized soil and treated with the following: i) uninoculated (-M); ii) inoculated with native AM fungal propagules (+M); or iii) inoculated with a Claroideoglomus claroideum (CC) strain isolated from non-contaminated soil. In each case, five Cu levels were applied to the soil (basal level 497.3 mg Cu kg-1): 0 (T1); 75 (T2); 150 (T3); 225 (T4); and 300 mg Cu kg-1 (T5). A high BRSP accumulation in AM inoculated treatments, especially with CC, was observed. A higher Cu-bound-to-BRSP content was found with increasing Cu concentrations, representing up to 20-22% of the total Cu in the soil. Moreover, a higher root Cu concentration in +M was observed. These results suggest a high Cu binding capacity by BRSP, which is a relevant aspect to consider in the design of bioremediation programs together with the selection of endemic metallophytes and AM fungal strains, which are able to produce glomalin at high quantities. <![CDATA[<b>Effects of organic and inorganic manures on maize and their residual impact on soil physico-chemical properties</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100003&lng=es&nrm=iso&tlng=es Organic and inorganic nutrients are important for crop productivity and soil health. Present study investigated the effects of organic and inorganic manures on maize and their residual impacts on soil physico-chemical characteristics. Sheep manure (SM), poultry manure (PM) and farmyard manure (FYM) were applied as organic nutrient source while urea, diammonium phosphate (DAP) and sulphate of potash (SOP) were used at different concentrations as inorganic nutrients source viz., T1: Unfertilized control; T2: NPK at 250-150-125 kg ha-1; T3: SM at 15 t ha-1; T4: FYM at 16 t ha-1; T5: PM at 13 t ha-1; T6: NPK at 150-85-50 + 8 t ha-1 SM; T7: NPK at 150-85-50 + 8.5 t ha-1 FYM and T8: NPK at 150-85-50 + 7 t ha-1 PM. Results showed that growth and yield of maize were substantially improved by fertilizer application alongside organic manures whereas soil total organic C and total N, P, K contents increased when inorganic fertilizers were applied alone or in combined with organic manures. However, soil pH and soil bulk density decreased due to application of organic fertilizer and showed a negative correlation with grain yield. Further, a significant and positive correlation (R²= 0.52, 0.91 and 0.55) was observed among maize grain yield and available N, P and K contents, respectively in the soil. Conclusively, integration of inorganic fertilizers with organic manures can be used with optimum rates to improve crop productivity on sustainable basis. This study will be helpful in crafting sustainable nutrient management programs in future to enhance crop productivity with high efficiency and minimum nutrient loss. <![CDATA[<b>Foliar application of Zinc and Boron improved the productivity and net returns of maize grown under rainfed conditions of Pothwar plateau</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100004&lng=es&nrm=iso&tlng=es Under rainfed conditions, farmers rarely use micro-nutrients for crop production, due to which soils become deficient especially in zinc (Zn) and boron (B). Secondly, farmers apply nutrients through soil application but scarcity/less availability of moisture make the nutrients unavailable for crop plants. Under such circumstances, foliar application of Zn and B may play a key role for better crop growth and yield. Therefore this field study was conducted to investigate the role of Zn and B application alone and in combination through seed, soil and foliar application methods on growth, yield and net returns of maize grown under rainfed conditions. Results showed that combined application of Zn and B on foliage improved relative water contents, SPAD chlorophyll values, leaf area index (LAI), crop growth rate (CGR), and grain yield due to substantial expansion in entire yield related traits. Combined foliar application of Zn and B harvested 12% and 45% more yield compared with seed priming and control treatments, respectively. The foliar application of Zn and B in combination counteracted the low rainfall effect by producing higher relative water contents that helped in improving SPAD-chlorophyll values, LAI and CGR. Higher net returns and benefit: cost ratio was also obtained by foliar application of Zn and B in combination. In conclusion, combined foliar application of B and Zn improved maize yield due to significant expansion in allometric and yield related traits and thus improved net returns of maize grown under rainfed conditions of Pothwar plateu in Pakistan. <![CDATA[<b>Differential vineyard fertilizer management based on nutrient<sup>,</sup>s spatio-temporal variability</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100005&lng=es&nrm=iso&tlng=es Conventionally, vineyard fertilizer management has been based on information from composite soil samples and no account has been taken of the existing spatial variability in soil fertility. This study presents a quantitative analysis of soil phosphorus (P2O5) and potassium (K2O) content as well as pH carried out in an 80 ha vineyard, during 2011 and 2013 in order to identify their spatial variability and temporal stability. Additionally a quantitative analysis of plant P2O5 and K2O content was carried out in 2013 with the objective of evaluating the spatial variability of plant nutrients.In 2013 a contact sensor was used to survey soil apparent electrical conductivity (ECa) and an active optical sensor was used to measure the plant Normalized Difference Vegetation Index (NDVI). The results showed a low potential for implementing site-specific management of phosphorus fertilizer but an interesting potential for implementing site-specific management of potassium fertilizer and pH correction. The concentration of P2O5 and K2O in the plant showed a CV<30%, with adequate values in almost the entire area of the field, in contrast to the concentration of these main macronutrients in the topsoil. These results show that for differential nutrient management of vineyards, plant nutrient concentration is a more stable tool than soil nutrients concentration. The ECa and the NDVI presented weak correlations with soil and plant concentration of, , respectively, P2O5 and K2O, which shows that further development of vegetation operational sensors is needed to support decision making in the vineyard fertilization management. <![CDATA[<b>Response of microbial activity to labile C addition in sandy soil from semi-arid woodland is influenced by vegetation patch and wildfire</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100006&lng=es&nrm=iso&tlng=es Nutrient cycling in semi-arid woodlands is likely to be influenced by patchy vegetation, wildfire and the supply of easily available organic C, e.g. root exudates. The study assessed the effect of wildfire and vegetation patch on response of microbial activity to labile C addition in soil from a semi-arid Eucalyptus woodland. Two sites were studied: one unburnt and the other exposed to wildfire four-month before sampling. Top soil (0 - 30 cm) from under trees, under shrubs or in open areas from each site was air-dried and sieved to < 2 mm. The soils were incubated at 80% of maximum water holding capacity for 24 days without or with addition of 5 g C kg-1 as glucose. Soil organic carbon (TOC), microbial biomass C, N and P availability and cumulative respiration were greater under trees than in open areas. Fire decreased TOC and cumulative respiration only under trees and had little effect on available N, microbial biomass C and P concentrations. The greater increase in cumulative respiration by glucose addition under shrubs and in open areas compared to under trees and, in a given patch, greater in burnt than unburnt soils, indicate lower availability of native organic carbon. <![CDATA[<b>Nitrogen availability and early corn growth on plowed and no-till soils amended with different types of cover crops</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100007&lng=es&nrm=iso&tlng=es Heavy application of nitrogen (N) fertilizers to agroecosystems contributes to water pollution and emission of nitrous oxide (N2O), an atmospheric constituent implicated in the greenhouse effect and stratospheric ozone depletion. The incorporation of cover crops biomass into agricultural soil is a practice that could provide a portion of the N needed by growing crops, and thereby could help reduce N fertilizer input and N loss from agroecosystems. Although the cover crop composition and the tillage management history of receiving soils could affect the pattern of mineral N release and its fates, these questions have not been addressed in previous research. A greenhouse experiment (85 d) was conducted to investigate the effects of two cover crops, hairy vetch (Vicia villosa, C/N: 11) and rye (Secale cereale, C/N: 82) on mineral N flux, N2O emission, and corn growth in soils under no-till (NT, 11 years) and plow-till (PT). Overall, tillage practice had only a marginal influence on N dynamics. Although NO3- flux was enhanced by both cover crops, the NO3- released was more efficiently utilized in the rye treatment. Corn growth and N uptake were significantly greater (P<0.02; 1.5 times) with rye compared to the vetch treatment. Conversely, N2O emission was significantly (P<0.03) higher with vetch than rye addition, with cumulative emission (across PT and NT) averaging 2.45 kg N ha-1 with vetch and 1.28 kg N ha-1 with rye addition. Positive relationships were found between NO3- flux and N2O emission, with the slopes of the regression lines suggesting a greater propensity of NO3- released from vetch to be converted into N2O. By leading to less N2O emission and better corn N uptake, the study results indicate that rye is a better cover crop option than vetch, regardless of tillage practice. <![CDATA[<b>Incidence of <i>Listronotus bonariensis</i> (Coleoptera: Curculionidae) in ryegrass pastures from southern Chile. New background</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100008&lng=es&nrm=iso&tlng=es The Argentine stem weevil, Listronotus bonariensis, is an important pest in pastures, especially ryegrass (Lolium sp.), compromising grassland persistence and productivity. Both, adult and specially larvae cause severe damage, action that generate the death of the tiller and reducing forage production. Chemical control has limited effectiveness in adult’s insect and negative effects on the environmental and toxicity to pollinators when applied close to the flowering period is observed. Therefore, the main currently strategy is based on the use of cultivars of Lolium endophyte fungus-infected with Neothypodium genus. However, over a decade that there are no reports on the presence of this weevil in southern Chile. Hence, the aim of this research was report the actual incidence of L. bonariensis in ryegrass pastures. The results of two years of prospecting showed that this weevil is currently causing damage to the ryegrass pastures indicating that the effectiveness of species infected with the fungus must be evaluated. <![CDATA[<b>Silicon fertilization reduces the deleterious effects of water deficit in sugarcane</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100009&lng=es&nrm=iso&tlng=es Few studies have focused on water deficit for sugarcane, whose damage could be reduced with Si, as shown in other crops. This study aimed to determine whether Si fertilization enhances the best recovery of sugarcane after two periods of the formative phase (tillering and early grand growth) for RB86-7515 (drought tolerant) and RB85-5536 (drought sensitive), and which growth phase is beneficial for each cultivar. It was investigated: 1) the effect of Si fertilization on total Si uptake, and on soluble Si in soil; 2) whether Si uptake could provided increased stalk yield, juice quality, dry biomass compared to well-watered treatments. Two experiments were conducted in pots under greenhouse: one with RB86-7515 and another with RB85-5536. Treatments were: 1-Non-Deficit+Si, 2-Non-Deficit-Si, 3-Early Deficit (ED)+Si, 4-ED-Si, 5-Late Deficit (LD)+Si, and 6-LD-Si. Silicon fertilization provided best recovery of sugarcane (superior sugar, stalk yield, and dry biomass) after early and late water deficit compared to its absence for both cultivars. For RB85-5536, Si fertilization propitiated similar recovery for water deficit and continuous irrigation treatments. No differences were observed between periods of water deficit. Therefore, Si fertilization at planting should be considered another tool for reducing the damage caused by water deficit in sugarcane. <![CDATA[<b>Effects of zinc application strategy on zinc content and productivity of chickpea grown under zinc deficient soils</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100010&lng=es&nrm=iso&tlng=es Field experiments were conducted at three locations with Zn deficient soils in southern Ethiopia during 2012 and 2013 cropping seasons to evaluate the effects of Zn fertilization strategies and varietal differences on Zn content and plant performance of chickpea (Cicer arietinum L.). Factorial combinations of three Zn fertilization strategies and five varieties were laid out in a randomized complete block design with three replications in each location and year. A combined analysis of variance was made using a mixed effects model. Zinc foliar application increased grain Zn content by 21 and 22% over Zn soil application and seed priming, respectively. The improvements were around four folds for straw Zn content for the same comparisons. Effects of Zn application strategies on gain and straw Zn contents were consistent across locations. The grain Zn concentration varied among the varieties ranging from 34 mg kg-1 for Mastewal to 42 mg kg-1 for the Landrace and variety Arerti. Zn application strategies did not affect the growth and yield parameters, except for pod bearing branches. Foliar Zn application and appropriate variety selection are potential approaches for Zn biofortification in chickpea. Further study aimed at identifying most effective spray timing for maximum grain quality response would be worthwhile to cut fertilizer and application costs. <![CDATA[<b>Native microorganisms as potent bioinoculants for plant growth promotion in shifting agriculture (<i>Jhum</i>)<i> </i>systems</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100011&lng=es&nrm=iso&tlng=es Microorganisms native to shifting cultivation were isolated and screened for plant growth promotion (PGP) properties. The bacterial and fungal isolates that exhibed production of indole compounds, siderophores, and ammonia; phosphate solubilization; and catalase activity, were selected and tested for their ability to promote the early growth of upland rice plants. Potential isolates from a preliminary seed germination assay carried out in plates were further tested in pots under greenhouse conditions. Observations after two and four weeks of growth indicated that all treated rice plants had higher shoot and root length than those in the control group. Of the isolates used in the experiment, the bacterial isolate SB5 and the fungal isolate SF4 exhibit higher growth activity, with growth increases of 26.20% and 15.87% respectively, over the control group. These isolates are being explored for consortium development as bioinoculants, in an attempt to restore the fertility of jhum fallows <![CDATA[<b>Water and temperature dynamics of Aquands under different uses in southern Chile</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100012&lng=es&nrm=iso&tlng=es Aquands are soils derived from holocenic volcanic ashes located in southern Chile. Due to the presence of very high levels of organic matter (30 %), these soils present a high total porosity (80 %) but at the same time, a limited water storage capacity due to their shallow soil depths. The aim of this work was to analyze the influence of land use change of a Duric Histic Placaquand (Ñadi) soil on soil physical properties and their consequences on water and temperature dynamics. The volumetric water content (qField) and soil temperature (T) were registered at different depths in a Ñadi soil under a secondary native forest (sNF) and naturalized grassland (NG). Undisturbed soil samples were collected to analyze the water retention curve, saturated (Ks) and unsaturated (Ku) hydraulic conductivity and water repellency. The dynamics of rainfall and water table depth (WT) were registered using a rain gauge and groundwater wells. The land use change of a Ñadi soil from sNF to NG induced soil structural changes in the first 15 cm of soil reducing the amount of macropores under NG and affecting the hydraulic conductivity function as well as qField and T dynamics, i.e. while the WT in winter reached the soil surface in the NG, under sNF the air-filled pores were still present. Similarly, the T gradients increased as qField decreased, being more intensive under NG. A nonhomogeneous soil wetting and water infiltration was assessed, which can be related to an increased spatial water repellency, soil hydraulic properties and rainfalls. <![CDATA[<b>Grain sorghum nitrogen use as affected by planting practice and nitrogen rate</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100013&lng=es&nrm=iso&tlng=es Water and nitrogen supply are often the most critical factors limiting growth and yield in crop production. A study was carried out in 2006 and 2007 to determine N use efficiency of grain sorghum (Sorghum bicolor (L.) Moench) in dryland production at the University of Nebraska, Lincoln, Nebraska, South Central Agricultural Laboratory. The study evaluated three row planting arrangements (RPA) including all rows planted (s0), alternate rows planted (s1), and two rows planted alternated with two skipped rows (s2) in a complete factorial with plant populations (PP) of 75,000 and 150,000 plants ha-1 and N application rates of 0, 50, 100, and 150 kg N ha-1. The objectives of the study were to determine the optimum N rate, magnitude of N uptake, and N use efficiency (NUE) for grain sorghum under dryland conditions with different row configurations. Conventional planting out-yielded skip-row planting by 23 to 36% in each year. Percent N translocated from biomass to grain at physiological maturity at half bloom ranged from 29 to 35% in 2006 compared with 46 to 51% in 2007. The RPA x PP interaction affected internal NUE (IE N) in 2006 and 2007, and physiological NUE (PE N) in 2006. The RPA x N rate interaction affected partial factor productivity (PFP N) in 2006. <![CDATA[<b>Assesing the vertical movement of a nematicide in a sandy loam soil and its correspondence using a numerical model (HYDRUS 1D)</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100014&lng=es&nrm=iso&tlng=es A test under laboratory conditions was performed to typify and model the vertical movement of a nematicide (DiTera) applied at concentrations of 400, 700, and 1000 mg L-1 via drip irrigation to a sandy loam class soil confined in tanks of 1 m³. Vacuum extractometers were set up in the tank at different depths to obtain samples of soil solution starting 10 cm away from the drip emitter. HPLC was used to measure the nematicide concentration in the soil solution. Later HYDRUS 1D was used to model the vertical nematicide concentration considering homogeneous soil. Soil hydraulic parameters were obtained from laboratory experiments whereas the dispersion length was obtained by inverse estimation matching measured and modeled data. Laboratory results showed no significant differences in vertical nematicide (distribution considered a fraction of the initial concentration), having a higher concentration at the surface and decreasing gradually with the depth. The predictive model was able to describe te nematicide behavior of the nematicide according to controlled test, obtaining a R² of 0.97, a RMSE of 67.41 mg L-1, a RRMSE of 13.33% and a Nash of 0.92. These results confirm the proposed model; however, further studies on this issue are needed, considering different scenarios in laboratory conditions and thus scaling it up to field conditions. <![CDATA[<b>Effect of wastewater sludge application on enzyme activities in soil contaminated with crude oil</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100015&lng=es&nrm=iso&tlng=es Crude oil affects soil ecosystems, resulting in significant losses in soil quality. The objective of the present study was to evaluate the effects of hydrocarbon pollution (crude oil) on soil enzyme activities and determine the removal of total petroleum hydrocarbons (TPH) during an incubation period of 150 days. The potential use of wastewater sludge as a biostimulating agent in petroleum-contaminated soils was also evaluated. The degradation of crude oil in contaminated soil was significantly enhanced after the addition of wastewater sludge. The results also indicated that significant TPH degradation in crude oil-contaminated soils (80% for dose of 0.5% and 83% for dose of 5% at 18 °C) (94% for dose of 0.5% and 92% for dose of 5% at 28 °C) occurred after an incubation period of 150 days. Enhanced enzyme activity levels in contaminated soils indicated that crude oil (0.5% and 5%, w/w) stimulated microbial growth and enzyme activity in the soil environment. Urease activity (UA) levels in crude oil contaminated soils were generally higher than initial UA levels in soil during the incubation period. Soil UA exhibited a stronger response to petroleum treatment. Alkaline phosphatase (APA) and β-Glucosidase (BGA) activities were not affected crude oil pollution. However, contamination of crude oil had a negatively effect on soil dehydrogenase activity (DHA). <![CDATA[<b>Enhancing NO<sub>3</sub><sup>-</sup> supply confers NaCl tolerance by adjusting</b> <b>Cl<sup>-</sup> uptake and transport in</b> <b><i>G. max</i></b> <b>& <i>G. soja</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100016&lng=es&nrm=iso&tlng=es The objective of this work was to elucidate NO3- supply, Cl- toxicity, and Cl-/NO3-interaction in Glycine max and Glycine soja under salt stress. G. max cultivars (Lee68 and Jackson) and G. soja accessions (BB52 and N23227) with different salt tolerance were chosen as the experimental materials. Effects of low (0.75 mmol/L), normal (7.5 mmol/L), and high (15 mmol/L) NO3- supply on growth, relative electrolytic leakage, and contents of Cl-, NO3-, Na+, K+ in roots and leaves of NaCl (50 and 100 mmol/L)-stressed plants were investigated. Results showed that, low NO3- supply led to serious salt damage on G. max and G. soja plants. While enhanced NO3- supply could significantly reduce relative electrolytic leakage and contents of Na+ and Cl- in roots and leaves accompanying with obvious NO3- increase and K+ maintenance. Thus, finally an improved growth and alleviated salt injury by reducing Cl-/NO3- and Na+/K+ ratios, especially forthe relatively salt-sensitive Jackson and N23227 were obtained. Moreover, Cl-/NO3- and Na+/K+ ratios were significant or extreme significant positively correlated with relative electrolytic leakage, and significant or extreme significant negatively correlated with root vigor or plant fresh weight. It suggests that Cl-/NO3- ratio can be used as vital reference indexes as Na+/K+ for evaluating soybean salt tolerance. <![CDATA[<b>Nitrification and nitrogen mineralization in agricultural soils contaminated by copper mining activities in Central Chile</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100017&lng=es&nrm=iso&tlng=es Microbiological bioassays of nitrification and nitrogen mineralization have been used for evaluation of soil quality on metal-contaminated soils. We evaluated the effectiveness of nitrification and nitrogen mineralization bioassays as quality indicators of soil degradation caused by metal contamination. We performed standard tests based on protocols of ISO 14238 (2012) and ISO 15685 (2012) on 90 soil samples collected from agricultural areas in central Chile that were historically contaminated by mining activities. Potential nitrification rate (PNR) was best explained by pH and organic matter content (OM) (R²=0.32), while nitrogen mineralization (Nmin) was best explained by OM and clay content (R²=0.44). Following normalization of the bioassays responses with respect to OM yielded significant correlations between PNR and pH and total Cu content (R²=0.22), and between Nmin and clay and total Cu contents (R²=0.19). However, inasmuch as total Cu content improved the regression model showing the inhibitory effect of Cu in both bioassays, it accounted for a mere small proportion of the variance. This was despite the wide range of Cu contents in the soils studied (51-2878 mg kg-1). Hence, due to the known sensitivity of the nitrification and nitrogen mineralization process to physicochemical characteristics of soils, these bioassays seem to have limited applicability for metal toxicity assessment in metal-contaminated soils. <![CDATA[<b>Compost, leonardite, and zeolite impacts on soil microbial community under barley crops</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100018&lng=es&nrm=iso&tlng=es There is little information about the potential effects of compost and zeolite or zeolite with leonardite as soil amendments in barley cultivation. Thus in this study, the following objectives were proposed: i) to compare the effects of the addition of compost, alone or simultaneously with zeolite, and of the addition of leonardite-enriched zeolite with those of the conventional NPK fertilization used in barley cultivation, on the soil nutritional status, microbial community structure, and enzyme activity in different stages of barley cultivation; and ii) to establish relationships between the different soil parameter trends, soil microbial community structure, and barley crop yield. In the field experiment carried out with a barley crop, the alternative fertilization treatments tested had an overall positive effect, in comparison with conventional fertilization with a mineral NPK fertilizer, when soil quality parameters, the nutritional level and yield of the barley crop were analyzed. Zeolite with leonardite increased barley yield in comparison with the compost treatments, either with zeolite or without, but had an excessive contribution to the water soluble contents of Na and N in soil. So, using environmental and agronomic criteria, the most rational action would be the use of compost in agriculture. <![CDATA[<b>Antifeedant activity of red clover root isoflavonoids on <i>Hylastinus obscurus</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100019&lng=es&nrm=iso&tlng=es In the last decade, there has been increasing interest in investigating the impact of flavonoids on insects, specifically for pest control. In this study, we investigated the impact of isoflavonoids upon the feeding behavior of the clover root borer, Hylastinus obscurus Marsham (Coleoptera: Curculionidae), which is one of the most serious global pests associated with red clover, Trifolium pratense L. Four aglycones isoflavonoids: genistein (1), formononetin (2), daidzein (3) and biochanin A (4) were isolated and identified by HPLC, from roots of two Chilean red clover cultivars. The first two compounds, formononetin (2) and genistein (), showed high feeding deterrent activity when they were evaluated in artificial diets. This antifeedant effect of isoflavones on feeding behavior of H. obscurus suggests that they are responsible for a decreasedin insect weight gain as compared with the control. This information could be useful respectively, to farmers and researcher to produce and create plants resistant to curculionid. <![CDATA[<strong>Impact of different tillage practices on soil physical properties, nitrate leaching and yield attributes of maize (</strong><em><b>Zea mays</b></em><strong> L.)</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000100020&lng=es&nrm=iso&tlng=es Tillage, undoubtedly, is one of the most crucial practices to ameliorate crop productivity and maintain soil health. A field experiment was conducted at research farms; Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan to examine how soil properties and maize crop respond to different tillage strategies (minimum, conventional and deep tillage). Randomized complete block design (RCBD) was finalized for the experiment with three repeats. Maximum total biomass production and grain yield were recorded in case of deep tillage practices. Conventional tillage not only improved leaf area index but also harvest. Minimum tillage minimized the leaching of nutrients especially nitrates. Soil bulk density (Mg m-3), particle density, soil organic carbon (g kg-1), infiltration rate (mm hr-1), percent porosity (%) and soil saturated hydraulic conductivity (mm hr-1) got affected by different tillage practices. Minimum tillage is suggested to avoid leaching losses of nutrients, this loss reduces the crop productivity.