Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> https://scielo.conicyt.cl/rss.php?pid=0718-951620180002&lang=es vol. 18 num. 2 lang. es <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[Nutrient abundance and variability from soils in the coast of king George Island]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200294&lng=es&nrm=iso&tlng=es Abstract: The goal of the study was to assess the levels of plant available nutrients in the soils of the Antarctic oasis of Point Thomas in the vicinity of Polish Antarctic Station H. Arctowski. Antarctic soils are undergoing transformations in the era of climatic changes and it is important to quantify changes in soil properties and determine the relationships between soil properties and ecological gradient. Total C and N were determined using CN analyser, mineral forms of nitrogen were determined colorimetrically, plant available P and K was analysed with Egner-Riehm method, Mg with Schachtschabel method and Fe, Mn, Cu, Zn were determined in 1M KCl using AAS (Atomic Absorption Spectrometry) method. The amounts of analysed compounds were dependent on organic matter, which was influenced by plant succession, and in some sites by the activity of seabirds. Most of organic matter was accumulated in the vicinity of penguin colony. All studied soils were abundant in plant available forms of studied macro- and micronutrients. In addition to translocation of biogens (mainly N and P) from the sea to the land by piscivorous birds, a dispersion of biogens on the entire ice-free area occurs. It is related to the occasional appearance of scua as well as the eolian topsoil dust input. <![CDATA[Changes in regional grain yield responses to chemical fertilizer use in China over the last 20 years]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200312&lng=es&nrm=iso&tlng=es Abstract: A major challenge facing China is to meet the increasing food demand of its growing population in the face of decreasing arable land area, while sustaining or improving soil productivity and avoiding adverse environmental impacts from intensive agriculture. This study uses data from China Statistical Yearbooks to analyze trends in regional soil productivity and grain yields in the major grain-producing regions in North China (NC), Northeast China (NE), East China (EC), Central China (CC), and Southwest China (SW), associated with regional fertilizer use and annual climate variation in rainfall and mean temperature over the 20 years. During 1992-2012, the average fertilizer increase rates (in kg ha-1 year-1) were in the order of regions CC (6.6) &gt; NC (4.8) &gt; EC (2.4) &gt; SW (2.1) &gt; NE (1.3), while yield responses to fertilizer use (with regression model coefficients, in kg kg-1) were in the order: SW (-0.9) &lt; CC (1.1) &lt; NC (1.7) &lt; EC (5.7) &lt; NE (9.3), showing higher yield responses to fertilizer use for NE and EC than for other regions. The changes in regional grain yields also showed higher yield responses to soil-based productivity for NC, CC, and SW, or to annual climate variability for CC than for other regions, indicating that other factors (such as inherent soil productivity or annual climate variability could be more important than fertilizer in affecting yields. The strategies for regulating nutrient management are needed considerably based on regional indigenous soil nutrient supply under varying regional climate conditions. <![CDATA[Water relations and growth response to drought stress of <em>Prosopis tamarugo</em> Phil. A review]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200329&lng=es&nrm=iso&tlng=es Abstract: Understanding the physiological mechanisms of response that allow plants to survive under suboptimal conditions such as drought stress is of particular interest, because of global climate change that threat the suitability of most terrestrial habitats for plant growth, as well as habitat disturbance of desert plants due to water extraction for human supply. Prosopis tamarugo Phil. of the Pampa del Tamarugal is frequently subjected to drought stress due to groundwater extraction for urban areas, mining industry and agriculture supply. The aim of this review is to analyze information concerning the plant growth response to drought stress and specifically P. tamarugo water relations and growth response to drought stress. P. tamarugo, being a desert plant, has physiological mechanisms that permit its adaptation to extreme environmental conditions like the Pampa del Tamarugal. It has mechanisms as osmotic adjustment, that allow some growth through osmoregulation; changes the angle of its leaflets to avoid high levels of radiation in the afternoon; partially closes its stomata to decrease water loss; maintains high stomata conductance to deal with increasing temperature and atmospheric demand. <![CDATA[Diatomaceous earth as source of silicon on the growth and yield of rice in contrasted soils of Southern India]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200344&lng=es&nrm=iso&tlng=es Abstract: Application of diatomaceous earth (DE) could improve the quality of soil, but its application in agriculture as a Si fertilizer requires additional research. Pot experiments were conducted with graded levels (0, 150, 300, 600 kg ha-1) of DE with recommended dose of N, P, K, in three types of soil (acidic, neutral and alkaline) from Southern India under two moisture conditions (field capacity and submergence) using rice as a test crop. The chosen DE consisted of biogenic silica, smectite, kaolinite and quartz. The grain yield was lower in plants grown in FC than in SUB moisture conditions regardless of the soil type and the DE added. Higher grain yield was observed with different DE applications under the SUB moisture condition in the three soils. The Si uptake increased for acidic and alkaline soils but not for neutral soil under the SUB moisture condition, whereas under the FC condition, the Si uptake was increased over the control only in alkaline soil. Increased nutrient and Si uptake was explained by the combination of physical and chemical properties of DE and was not only due to the contribution of amorphous silica. DE might be useful for improving the crop yield, but the soil composition and water regimes play a key role that influences the availability of nutrients in soils. <![CDATA[Distribution of C and inorganic phosphorus fractions in different aggregate sizes under forestry, agroforestry system and pasture]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200361&lng=es&nrm=iso&tlng=es Abstract: The objective of this study was to evaluate the organic carbon (OC) distribution and inorganic phosphorus (P) fractions on different soil aggregates classes under forestry fragment of Atlantic Forest, pasture and agroforestry managed for a long period. Soil samples were collected at depths of 0.00-0.10, 0.10-0.20 and 0.20-0.60 m, and the aggregate stability analysis was performed at each depth. The OC and the inorganic P fractions (Pbic readily available, NaHCO3 0.5 mol L-1; PNa1 moderately available, NaOH 0.1 mol L-1; and PNa2 restricted availability, NaOH 0.5 mol L-1) were determined in the respective classes of soil aggregates 4-2, 2-1, 1-0.5, 0.5-0.25 mm. Soil under forestry fragment showed higher OC contents and regardless the land use, highest values of inorganic P were found in the aggregates &gt; 1 mm. Forestry showed highest levels of Pbic, while agroforestry showed the highest levels of PNa1, and pasture had highest values of PNa2. <![CDATA[Standardization of critical boron level in soil and leaves of coconut palms grown in a tropical Entisol]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200376&lng=es&nrm=iso&tlng=es Abstract: An experiment was conducted to standardize the critical boron level in soil and leaf samples of coconut palms grown in a typical Entisol of the Onattukara region of Kerala, India. Graded levels of boron as borax were applied at 0, 6, 12, 18 and 24 g per palm per year in four split doses. The critical boron level in soil and leaves was standardized using the following methods: the Cate and Nelson graphical (CN) method, the Mistcherlich equation (ME), and the quadratic plateau response (QP) method. In the CN method, the critical level of boron in soil and leaves was 0.48 mg kg-1 and 11.5 mg kg-1, respectively. In the ME model, the critical boron level in soil and leaves was 0.46 mg kg-1 and 7.55 mg kg-1, respectively. In the QP response curve, the critical level of boron in soil was estimated to be 0.87 mg kg-1, and in the leaf, the critical level was found to be 13.27 mg kg-1. Because the level estimated via the graphical method and by the Mistcherlich equation is similar with regard to the soil boron, 0.48 mg kg-1 can be considered as the critical boron level in soil. Regarding the critical boron level in the leaf, values estimated via the CN method and the QP response curve are in proximity, and, hence, the critical boron level in leaf is 13.27 mg kg-1. These results suggest that the application of 160 g of borax in four split doses when the levels of boron in soil and leaves fall below the estimated critical values for better use efficiency. <![CDATA[Nutritional status of yellow passion fruit fertilized with phosphorus sources and doses]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200388&lng=es&nrm=iso&tlng=es Abstract: Phosphorus is important to plant growth due to its storage and energy transference processes and its involvement in the active absorption of other nutrients. The aim of this study was to evaluate the nutritional status of yellow passion fruit plants under fertilization from different P2O5 sources and rates. Treatments were distributed in randomized blocks in a 2 × 5 factorial design, with two phosphorus sources (simple and triple superphosphate) and five P2O5 doses of 0, 12, 18, 24 and 30 g hole-1. A total of two applications were performed at 60 and 120 days after seedling transplanting; P2O5 doses of 0, 24, 36, 48 and 60 g hole-1 were equivalent to 0, 27, 40, 53 and 67 kg hole-1 of P2O5 from each superphosphate source, respectively. When the orchard was in fructification, 150 days after seedling transplanting, individual leaf samples were harvested from the median branches of the plants in each parcel in order to evaluate N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Zn and Na contents. The phosphate fertilization promoted adequate nutrition for passion fruit plants of N, P, K, Mg and S, independent of the source provided, but adequate Ca only for doses up to 36 g hole-1 of P2O5. Plants were impaired in B, Cu, Fe and Mn, except for Fe in those not fertilized with P2O5 and those treated with 24 and 36 g hole-1 of P2O5 in simple superphosphate form. Considering the adequate nutritional value of passion fruit, it is recommended to fertilize with 36 g hole-1 year-1 of P2O5, whether simple or triple superphosphate. <![CDATA[Nutritional status and production of noni plants fertilized with manure and potassium]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200403&lng=es&nrm=iso&tlng=es Abstract Noni is a fruit species cultivated around the world, including Brazil however, scientific information about its nutritional status are scarce, thus justifying the need for more research on this topic to enhance its productive yield. This study aim is to evaluate both the mineral foliar composition and the productivity of noni plants cultivated in soil with cattle manure and potassium (K). The experiment was conducted from July 2012 to November 2013 at the Universidade Federal da Paraíba, Municipality of Bananeiras, Paraíba State. Treatments were organised according to a 5 × 2 factorial design involving five doses of KCl (0; 13.2; 37.5; 61.5; and 69.6 g plant-1) in soil without cattle manure and with 4 kg plant-1, in randomized blocks, with four repetitions and three plants per plot. The number of noni fruits harvested by plants fertilized with cattle manure increased from 51 to 70 fruits plant-1. Compared to coffee trees, noni plants were adequately supplied with nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron and zinc, but they were deficient in boron and manganese. The application of cattle manure to soil promoted contents of phosphorus and potassium in foliar samples, positively affecting the fruit formation and the production of noni plants. <![CDATA[Carbon dynamics, potential and cost of carbon sequestration in double rice cropping system in semi arid southern India]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200418&lng=es&nrm=iso&tlng=es Abstract: Studying the dynamics of soil organic carbon (SOC) is important for understanding the mechanistic pathways of C stabilization into different SOC pools. An attempt was, therefore, made to assess the impact of double rice cropping system with different levels of fertilizers and in combination with organics on C sequestration and its stabilization in an Inceptisol using a 14-year old experiment at Jagtial under semi-arid climate in India. Total organic carbon (TOC) allocated into different pools in order of very labile &gt; less labile &gt; non labile &gt; labile, constituting about 41.4, 20.6, 19.3 and 18.7%, respectively. In comparison with control, system receiving farmyard manure (FYM-10 Mg ha-1 season-1) alone showed greater C build up (40.5%) followed by 100% NPK+FYM (120:60:40 kg N,P,K ha-1+5 Mg FYM ha-1season-1)(16.2%). In fact, a net depletion of carbon stock was observed with 50% NPK (-1.2 Mg ha-1) and control (-1.8 Mg ha-1) treatments. Only 28.9% of C applied through FYM was stabilized as SOC. A minimal input of 2.34 Mg C ha-1 y-1 is needed to maintain SOC level. Treatments with organics showed a higher carbon management index, and microbial biomass and other labile pools of SOC. Results also indicated that100% NPK+FYM could maintain yield sustainability with a lower cost of carbon sequestration. <![CDATA[Early-stage changes in chemical phosphorus speciation induced by liming deforested soils]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200435&lng=es&nrm=iso&tlng=es Abstract A hypothesis of whether an increase in Ca2+ due to liming acid soils causes an increase in Ca-phosphates with a concomitant decrease in Al- and Fe-phosphates was tested on a relatively short-term time frame, as observed in the investigations of chemical phosphorus (P) speciation. Soil samples were taken at a deforested site and split into three treatment groups: a control and two CaCO3 treatments (0.1 and 0.4 g CaCO3 in 100 g soil). Each soil was incubated at 25±2°C for 40 days. Inorganic-P was partitioned into three fractions: Fraction-A (Al- and occluded Fe-P), Fraction-B (non-occluded Fe- and adsorbed-P), and Fraction-C (Ca-P). The pH of CaCO3-treated soils decreased right after liming, indicating a probable formation of solid phosphate compounds. Available P in CaCO3-treated soils decreased from 0.67 mg kg-1 to control levels at the end of incubation. Total-P and organic-P of CaCO3-treated soils were virtually the same as those of control soils, while inorganic-P varied. Fraction-A in both CaCO3-treated soils peaked at 10 days of incubation, and then decreased below control levels, while Fraction-B decreased abruptly right after liming, and thereafter gradually decreased. Liming decreased Fraction-C, and caused an increase in Al- and Fe-P due to an increase in exchangeable Al3+ and Fe3+. Our results challenge the hypothesis by showing the unexpected opposite data for Al-, Fe- and Ca-P compounds at least in the early stage of equilibrium disturbances due to liming an acidic soil. <![CDATA[Nitrogen mineralization simulation dynamic in tobacco soil]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200448&lng=es&nrm=iso&tlng=es Abstract Laboratory and field culture experiments have been carried out at two sites which show that temperature and soil moisture significantly affected nitrogen mineralization in the soil in a tobacco field. Intermittent leaching under aerobic incubation conditions was adopted to develop dynamic simulation models of organic nitrogen mineralization under different temperature regimes (10, 15, 20, 25, 30, 35, 30, 25, and 20 °C) and soil gravimetric moisture content (0.1, 7%, 13%, 20%, 27%, 33%, 40%, 47%, and 53%). The results show that the highest N mineralization rate appeared at 35°C and the lowest was 10°C. Soil N mineralization rate, as affected by soil moisture, is a single peak curve with a peak at 40%. The interaction of temperature and moisture on soil N mineralization is significant. Based on the results of a field trial, the combined model given by governing equation: has been established to simulate the dynamics of soil N mineralization under tobacco field conditions. A validation experiment showed that the measured values of mineralized N accumulation in the two experimental sites had a good correlation with the simulated values, indicating the practical value of the proposed model. <![CDATA[A comparative study of phosphorus availability in an acidic soil and an alkaline soil amended with organic and inorganic phosphorus sources]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200466&lng=es&nrm=iso&tlng=es Abstract An incubation study was conducted to investigate the effects of adding cow manure (CM), poultry manure (PM), city waste (CW) and triple super phosphate (TSP) on extractable P in a sandy loam acidic soil (Aquepts) and a silt loam alkaline soil (Fluvents). Phosphorus was added at a rate of 200 mg P kg−1 to the soil in the forms of CM, PM, CW and TSP. The soil was incubated at field capacity for 15, 30 and 60 days after which the P sources were extracted with Olsen, Kelowna, Mehlich-3, and Bray and Kurtz-II extractants. Regardless of the extractants and soils, after 15 days of incubation, the highest extractable P source was the TSP (88-97 mg kg-1 as Olsen P), and the lowest was the CW (11-15 mg kg-1 as Olsen P). The extractable P levels with the CM (41-48 mg kg-1 as Olsen P) and PM (71-73 mg kg-1 as Olsen P) were between the extractable P levels with the TSP and CW. Extractable P in the soils with the organic amendments increased slightly with increasing incubation time from 15 to 60 days. With the TSP, extractable P decreased sharply in the acidic soil, while it decreased gradually in the alkaline soil. In both soils, extraction efficiency was in the order of Bray and Kurtz-II&gt; Mehlich-3&gt; Kelowna&gt;Olsen. The efficiency of the added P as measured by NaHCO3 increased with the organic amendments, while the efficiency decreased with the TSP with days of incubation. This study indicates that soil samples taken 30 days after the addition of CM and PM in the soil might reflect the most plant-available P. <![CDATA[Ammonia and nitrous oxide emissions as affected by nitrification and urease inhibitors]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200479&lng=es&nrm=iso&tlng=es Abstract Nitrogen (N) gaseous losses have environmental and economic implications. Ammonia (NH3) volatilization and nitrous oxide (N2O) emissions from a volcanic soil were concurrently quantified using intact lysimeters, after application of the equivalent to 100 kg N ha-1 with and without urease (NBPT) and nitrification (DCD) inhibitor: Urea, Urea+NBPT, Urea+DCD, Dairy slurry and Dairy slurry+DCD. A control treatment (-N) was also included. Treatments were distributed on a randomized block design and evaluated during 28 days. Ammonia was analyzed for NH4 by colorimetry, while N2O was estimated by gas chromatography. Total emissions were estimated by addition of daily fluxes, and results were analyzed by ANOVA. Ammonia was the main N loss, with 35 to 43% and 5% to 16% of the total N applied in Urea and Dairy slurry (P&lt;0.01), respectively, with and without inhibitors (P&gt;0.05). The use of DCD reduced N2O emissions by 44 and 8% in the same treatments, respectively (P&lt;0.05). Results suggest that DCD has a potential as a mitigation option in grassland volcanic soils reducing N2O losses. The use of NBPT did not reduce NH3 losses and N2O emissions when applied with urea. Concurrent N gasses losses from soil showed that indirect N2O losses following NH3 volatilization might be more relevant in volcanic soils than direct N2O losses. <![CDATA[<em>Nothofagus pumilio</em> forest affected by recent tephra deposition in northern Patagonia. I- Environmental traits influencing seedling growth]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200487&lng=es&nrm=iso&tlng=es Abstract The 2011 Puyehue-Cordón Caulle volcanic eruption left vast areas of Nothofagus pumilio forests covered by high volumes of tephra, which buried the understory. This event offered a unique opportunity to analyse the impact of recent tephra deposition and the main environmental factors affecting the growth of N. pumilio seedlings. To this end, three study sites were selected and sampled three years after the eruption, two with a thick tephra layer (50 cm) but with different tree conditions: i) most trees alive or ii) most trees dead, and a third site, iii) with minimal tephra deposition. From each site, five N. pumilio 18-month-old seedlings were collected, morphometrically measured (shoot, epicotyl and main root length; shoot, epicotyl and root collar diameter), and environmental factors were also registered (light intensity, soil pH and conductivity, available P, bulk and particle soil density, and porosity). The main results indicated that three years after eruption the site with tephra deposition and dead trees (the most near to the crater) had the biggest seedlings, the lowest pH and the highest values for available P and light intensity. This temporally unique geological event showed that the regeneration potentiality of N. pumilio is high when environmental factors allow direct incident light on a substrate with high mineral content, even when the environment has previously been subjected to a significant degree of disturbance. Given the recurrence of volcanic events in Northern Patagonia, this subject merits further long-term study. <![CDATA[<em>Nothofagus pumilio</em> forest affected by recent tephra deposition in northern Patagonia. II- Shifts in diversity and structure of rhizosphere fungal communities]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200499&lng=es&nrm=iso&tlng=es Abstract Volcanic eruptions have a significant effect on ecosystems, including soil and its fungal communities. Due to the eruption of the Puyehue-Cordón Caulle in 2011, thick tephra deposits accumulated in several Nothofagus pumilio forests in Northern Patagonia. The tephra deposition affected plant establishment and development during the post-eruption period. In this work we analyzed rhizosphere fungal communities associated with N. pumilio seedlings at three study sites sampled three years after the eruption, two with a thick tephra layer (50 cm) and a third site with no tephra deposition. Denaturing gradient gel electrophoresis (DGGE) was performed for the different fungal communities (Ascomycetes, Basidiomycetes and Total fungi). We found clear shifts in rhizosphere fungal communities, especially for Basidiomycetes and Total fungi. Site-related characteristics, such as type of substrate, light intensity and the existence of understory and previous mycelial networks, seemed to be the main factors determining the structure of these fungal communities. Given their sensitivity to different types of environmental change, these microbial communities could be used as bioindicators. Specifically, Basidiomycetes and total fungi seem to be better bioindicators of environmental changes than ascomycetes. The results shown here contribute to the understanding of how fungal communities respond to disturbance, an important issue in the evaluation of how ecosystem processes might be affected in areas commonly subjected to geological risks, such as volcanism. This information is also relevant to the planning and successful implementation of restoration activities based on seedling optimization by rhizosphere fungi. <![CDATA[Critical limits of Mehlich 3 extractable phosphorous, potassium, sulfur, boron and zinc in soils for nutrition of rice ( <em>Oryza sativa</em> L.)]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200512&lng=es&nrm=iso&tlng=es Abstract: We evaluated the critical limits of P, K, S, B and Zn in Inceptisols and Alfisols for nutrition of rice (Oryza sativa L.) using Mehlich 3 as an extractant. Three levels, each of P (0, 14 and 23 mg kg-1 soil), K (0, 23 and 36 mg kg-1 soil), S (0, 4.5 and 9.0 mg kg-1 soil), B (0, 0.5 and 1.0 mg kg1 soil) and Zn (0, 2.3 and 4.5 mg kg-1 soil) were applied separately to 20 Alfisols and Inceptisols each for growing rice in greenhouse. Biomass yield, concentration and uptake of those nutrients by rice were significantly influenced (P ≤ 0.01) by the soil and rate of each of the nutrients (P, K, S, B and Zn), but not by their interactions in both the soil orders. The amount of these five nutrients as extracted from soils by Mehlich 3, alike conventional extractants, showed significant positive correlations (P≤ 0.01) with biomass yield, nutrients concentration and their uptake by rice plant, which indicated suitability of Mehlich 3 in predicting plant available nutrients in soil. The critical levels of Mehlich 3 extractable P, K, S, B and Zn for rice in Inceptisols were 14.7, 51.2, 22.9, 0.65 and 1.27 mg kg-1; while in Alfisols those values were 8.2, 117.3, 21.9, 0.40 and 2.15 mg kg-1, respectively. <![CDATA[Nano iron (Fe) complex is an effective source of Fe for tobacco plants grown under low Fe supply]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200524&lng=es&nrm=iso&tlng=es Abstract: In order to compare the uptake, utilization and distribution of iron (Fe) as nano and bulk Fe complex (Fe(III)-EDTA), an experiment was conducted using hydroponically-grown Fe-deficient tobacco (Nicotiana rustica L.) plants. Plants were treated with Fe either through roots (root application, RA) or leaves (foliar application, FA). Leaf chlorophyll concentration and plants biomass responded to the Fe re-supply; this response was quicker for the nano Fe complex than the bulk Fe complex, in particular, in the RA plants. Plants re-supplied with the nano Fe complex had lower Fe content but higher Fe use efficiency than plants re-supplied with the bulk Fe complex. Analysis of different plant fractions at two subsequent weeks revealed that the nano Fe complex had higher mobility than the bulk Fe complex, both in the xylem and the phloem. Comparison of RA and FA revealed that the re-supply of Fe through roots was more efficient in retrieving the whole plant growth than the foliar Fe spray. RA, in contrast to FA plants, profited from an enhanced Fe uptake capacity induced under Fe starvation in the roots. Alternatively, FA was effective in extending the green leaf area duration. Our data suggested that nano Fe complex is advantageous as both leaf spray and a long-term feeding of plant through roots. <![CDATA[Impact of common reed and complex organic matter on the chemistry of acid sulfate soils]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200542&lng=es&nrm=iso&tlng=es Abstract: Acid sulfate soils (ASS) are naturally occurring soils or sediments formed under reducing conditions that either contain sulfuric acid or have the potentail to form it, in an amount that can have adverse imapcts on the environment. The negative impacts of ASS are associated with the release of acidity produced and the release of toxic metals and metaloids from solubulised soil matricies into the environment. It has been shown recently that addition to ASS of dead plant material as organic matter creates microenvironments for soil microbes to ameliorate sulfuric soil and prevent sulfidic soil oxidation. Initial breakdown of the organic matter results in an oxygen demand that generates anaerobic conditions conducive to the reduction of sulfate to sulfides by sulfate reducing bacteria using the residual organic material as a carbon source and causing the pH to rise. There is also evidence that live plants increase acidification, potentially by aerating the soil. In nature, plants shed dead material as they grow, so that both live and dead organic matter co-exist. It is not known what happens to ASS chemistry, particularly pH, under such natural conditions. In this study, Phragmites australis was used to examine the combined effect of growing plants and incorporated organic matter on ASS chemistry (pH, redox potential and sulfate content) under aerobic and anaerobic conditions. In almost all cases, live plants enhanced sulfuric soil acidity and sulfidic soil oxidation. The mechanism for these changes on ASS chemistry appears to be the facilitation of oxygen penetration into the soil via aerenchymatous tissues in the plant roots. <![CDATA[Dynamics of soil fertility and maize growth with lower environment impacts depending on a combination of organic and mineral fertilizer]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200556&lng=es&nrm=iso&tlng=es Abstract: The combined application of organic and mineral fertilizers is gaining recognition as a viable approach to address the decline of soil fertility in intensive cultivation. A four-year experiment was conducted to study the dynamics of maize growth and analyse environmental changes. Two treatments were designed, (І) mineral fertilizer treatments (MF) that received the optimal fertilization level with 185 kg N/ha, 60 kg P2O5/ha, and 90 kg K2O/ha and (П) the combination of organic and mineral fertilizer treatments (OMF) with the application of 3.75 t/ha organic fertilizer supplemented with 125 kg N ha-1. The results indicated that OMF could improve the maize yield by 9.7-13.6 %, while the aggregate environmental index was reduced by 17 % compared with MF. Principal component analysis (PCA) showed that OMF promotes maize growth and yield attributed to the increased N, P and K uptake at the 12-leaf stage and tasseling stage, and the increased urease activity and P uptakes at the harvest stage. Life cycle assessment (LCA) analysis indicated that OMF decreased energy consumption, greenhouse gas emissions, acidification and aquatic eutrophication compared with MF. The results clearly revealed that organic applied with less mineral fertilizer had a higher maize yield and lower agricultural environmental risk compared to only mineral fertilizer. <![CDATA[Nutrient and sediment losses to streams after intervention of Eucalyptus plantations]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-95162018000200576&lng=es&nrm=iso&tlng=es Abstract: The forestry industry is known for negatively affecting stream quality when proper management is not applied. Nutrient retention by soils and streamside vegetation buffer strips could attenuate these impacts. We tested the response of different streams to the nutrients and sediments released by a) fertilization and b) clear-cutting of Eucalyptus globulus plantations growing on volcanic soils in southern Chile. We expected the exports to decrease as the remnant streamside native forest width (SNFW) increased. The response to fertilization was restricted to the days immediately after the nutrient addition. On the contrary, most of the nutrients analysed (nitrate, ammonium, dissolved organic nitrogen, phosphate, and total phosphorus) showed a long-term response to clear-cutting. The observed trends were not affected by the SNFWs included in this study (2.5-22 m). Regarding sediments, there were no differences compared to the control watershed, probably due to improvements in the implemented management practices. We conclude that a SNFW &lt; 22 m is not sufficient to avoid the loss of nutrients released by clear-cutting, as it is for sediments. The analysed SNFWs were smaller than those established by Chilean regulations (maximum 30 m) and our results support claims for wider riparian widths in order to effectively filter the nutrients and sediments that influence streams.