Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 17 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Can biochar provide ammonium and nitrate to poor soils?</b>: <b>Soil column incubation</b>]]> Understanding how nitrogen concentrations respond to biochar amendment in different types of soils is important for agricultural management. Here, we analyzed the effects of amendment with rice hull biochar on sandy soil, red soil, and alkaline soil (coastal solonchak) over 13 months, focusing on factors such as ammonium (NH4+-N) and nitrate (NO3−-N) cumulative leachate losses, pH, cumulative volumes of leachates, NH4+-N and NO3−-N abundance of soils, soil dehydrogenase, and nitrogen-related soil enzyme activities. Our results indicated that biochar amendment increased the pH of red soil but decreased the pH of both sandy and coastal solonchak soils; promoted the retention of NH4+-N in red and sandy soils, but not in coastal solonchak; and reduced the loss of NO3−-N during the early stages of leaching but accelerated losses during subsequent leaching stages. Soil nitrogen supply capacity (NH4+-N + NO3−-N) greatly increased over the short term, with significant differences between treatments. Further, biochar enhanced concentrations of NH4+-N and NO3−-N in soils, and the addition of biochar stimulated the enzymatic and microbial activities in soil, which may increase the abundance of NH4+-N and NO3−-N. Finally, we found that the response of NH4+-N and NO3−-N to biochar addition varied among the different soil types. <![CDATA[<b>Absorption and distribution of cadmium of three maize hybrids in three environments</b>]]> Anthropogenic soil contamination with heavy metals has received much attention in recent years, especially cadmium (Cd), which is a very toxic element for human health and is exposure is mainly through contaminated food. Maize (Zea mays L.) is one of the most important cereals in the human diet that is characterized as species whose cultivars differ in Cd accumulation. Therefore, identifying and selecting low Cd-accumulating genetic material will contribute to reducing its ingestion. Among the agricultural crops that are important for Cd in the human diet is maize. Cadmium contents in three maize cultivars were grown under different environments conditions in Chile where soils were enriched with increasing Cd rates, were evaluated. Grain yield, Cd concentration in different plant tissues, and soil post-harvest, were evaluated. Results showed that grain yield was not affected by soil Cd; however, plant tissues generally exhibited differences in Cd concentration associated with the environment, La Serena showed the highest grain Cd accumulation (30 µg kg-1; P < 0.05). In addition, among cultivars, Pioneer showed the highest grain Cd concentration (19.5 µg kg-1; P < 0.05).. Grain Cd concentration of the three maize cultivars were within the range cited in the bibliography as not toxic. <![CDATA[<b>Xylem sap mineral analyses as a rapid method for estimation plant-availability of Fe, Zn and Mn in carbonate soils</b>: <b>a case study in cucumber</b>]]> Low plant-availability of iron (Fe), zinc (Zn) and manganese (Mn) leads to micronutrient deficiency, causing significant yield reductions of crops throughout the world, especially in calcareous soils. This study was performed in order to evaluate the efficiency of xylem sap analysis in the determination of Fe, Zn and Mn availability in plants (Cucumis sativus L.) affected by calcium carbonate (CaCO3) levels. A soil with six levels of CaCO3 (0−10% DW) was used. We performed a combination approach, including analysis of the soil mobility of micronutrients using different extractants (water, DTPA-TEA and ammonium acetate), as well as xylem and shoot elemental analysis. Generally, application of CaCO3 resulted in a pH increase of the bulk soil of 1.4−2.2 pH units; extractability of all micronutrients was significantly decreased 1.4−4.2 times, irrespective of the extracting solution. Xylem sap Fe, Zn and Mn concentrations were significantly correlated with the respective concentrations in the soil extracting solutions. By contrast, only shoot concentrations of Zn and Mn, but not of Fe, were linearly correlated with their extractable forms. With electrothermal atomic absorption spectrometry, changes in xylem sap concentrations of micronutrients were detected without preliminary mineralization of plant material, in contrast to shoot analysis. Our results demonstrate that xylem sap analysis offers the advantages of a simple characterization of multi-microelement availability in plants under CaCO3 stress. <![CDATA[<b>Optimization of potassium fertilization/nutrition for growth, physiological development, essential oil composition and antioxidant activity of <i>Lavandula angustifolia</i> Mill</b>]]> Lavandula angustifolia (Mill.) is a medicinal plant of great importance with a variety of applications in perfume and pharmaceutical industries or landscaping, but only limited information is available about its response to potassium supplementation. This experiment was conducted in order to determine the effects of potassium (K: 275-300-325-350-375 mg L-1) levels on the morphological and biochemical characteristics of lavender grown hydroponically. Results showed that K levels affected plant growth, mainly the root development while no differences were found for leaf chlorophyll content and stomatal conductance. Essential oil yield increased in the 300 mg L-1 in comparison to 275 or 325-375 mg L-1 of K application. The middle ranged K levels (300-325-350 mg L-1) enhanced leaf content in total phenols, flavonoids and antioxidant activity (DPPH, FRAP). Lipid peroxidation content (MDA) employed as damage index, was lower in the 325 mg L-1 of K treatment. No differences were observed in antioxidant enzymes (SOD, CAT, APX) activity and H2O2 content among K applications. The main constituents of leaves essential oil (1,8-cineole, borneol, camphor, α-terpineol, myrtenal) and mineral accumulation were affected by K treatments. Lavender grown in 300 mg L-1 of K was appropriate for the essential oil uses/production while the 325 mg L-1 of K were more appropriate for lavender cultivation for fresh and dry matter uses. <![CDATA[<b>Physiological and nutritional responses in two highbush blueberry cultivars exposed to deficiency and excess of boron</b>]]> Boron (B) is an essential micronutrient required for physiological and biochemical processes in fruit crops such as highbush blueberry (Vaccinium corymbosum L.), well adapted species to acidic soils (pHwater ≤ 5.5) with relatively low B availability. However, an optimal range of B supplies is quite narrow, particularly among cultivars, making it easy to under- or over-fertilize which could lead to boron toxicity. Under controlled conditions, cultivars Brigitta and Legacy were grown in a peat moss substrate(pH 4.5) with five B concentrations (0, 50, 200, 400 and 800 µM). Plant biomass, nutrient concentration, water potential (Ψleaf), oxidative stress and antioxidant activity were determined at 30 d. Concentrations of 400 and 800 µM B reduced shoot and root growth in both cultivars, and800 µM B decreased Ψleaf in Legacy and significantly increased it in Brigitta. Boron applied at 400 µM resulted in the highest B accumulation in leaves of Brigitta (5-fold) and Legacy (2-fold), whereas Brigitta roots showed up to 60% increased B accumulation in comparison with 50 µM B, respectively. High B caused more severe oxidative stress in leaves of Legacy than B deficiency. The antioxidant activity was increased from 50 to 400 µM B in both cultivars. Boron added at 400 and 800 µM impaired physiological and biochemical performance probably due to toxicity, demonstrating that highbush blueberry in a genotype-dependent manner has relatively low B requirement. <![CDATA[<b>Formation, properties and reactivity of coprecipitates and organomineral complexes in soil environments</b>]]> In soil environments the formation of simple coprecipitates formed by the interaction of two or more cations and/or anions are the rule and not the exception. In this review we describe the formation, the nature and the reactivity of coprecipitates formed by the interaction between cations (Fe, Al, Mg, Mn, Zn) with the formation of mixed oxides or layered double hydroxides (LDHs) and of coprecipitates formed by the interactions of inorganic and low molecular mass organic (LMMOLs) ligands with OH-Al and/or OH-Fe species both in the absence or presence of phyllosilicates. The presence of anions within these samples strongly affect the sorption of other ligands on the surfaces of the coprecipitates. Furthermore, the anions coprecipitated with Al and/or Fe hydrolytic products are only partially replaced even by ligands with strong affinity for the surfaces of the final samples, clearly because they are also incorporated into the network of the precipitates. We also describe the formation, surface properties and reactivity of binary complexes obtained by the interaction of hydrolytic products of Al and Fe with clay minerals and of ternary OH-Al(-Fe)-organics-phyllosilicates (organics included also large anions as tannate or proteins). The effect of the sequence of addition of the components of the final organomineral complexes influenced the physicochemical and mineralogical properties of the samples. Attention was also devoted to the stabilization of organic substances in organo-mineral coprecipitates and soils. <![CDATA[<strong>Iron-bearing minerals from soils developing on volcanic materials from Southern Chile</strong>: <strong>Mineralogical characterisation supported by Mössbauer spectroscopy</strong>]]> On this work, the iron oxide mineralogy of Chilean volcanic ashes derived soils have been reviewed, emphasizing on new finding linked to the application of Mössbauer spectroscopy. It has been established that free iron oxide layer contributes with positive variable surface charge to the clay-size soil particle, at soil pH. However, the importance of such contribution seems to depend on the evolutionary stage of the different volcanic soil orders, which defines the crystalline degree of their iron oxide contents. Mössbauer spectroscopy complemented with different physical, chemical and instrumental techniques revealed key aspects of iron oxide mineralogy on these Chilean volcanic soils. For instance, results for Ultisol revealed that the evolution of the soil particle could be followed just analysing the main component of their iron oxide mineralogy; thus, the iron oxide mineralogy change when passing from the volcanic ashes (magnetite), to sand-size magnetic separates (partially-oxidized magnetite), to silt-size (strongly-oxidized magnetite), and finally to clay-size (maghemite) soil samples. Therefore, it would seem that physical weathering of the Ultisol produces smaller and more oxidized particles. On the other hand, the Andisol samples, a young volcanic soil compared to Ultisol, seems to have a constant iron oxide mineralogy among all its different particle size fractions: paramagnetic Fe2+ and Fe3+ species with low crystalline degree, the last one possibly assignable to a ferrihydrite-like mineral. Therefore, on the case of Andisols, it seems that the high contents of organic matter somehow prevent mineral evolution towards higher oxidation and more crystalline levels, in agreement with past studies. <![CDATA[<b>Improvement of cold stress resistance via free radical scavenging ability</b> <b>and promoted water status and photosynthetic capacity of gallic acid in soybean leaves</b>]]> Plant polyphenols exhibit a wide variety of biological activities such as antimutagenicity, anticarcinogenicity and antioxidative activity. There is no report whether gallic acid (GLA), a naturally occurring plant phenol, is able to activate the plant defense system under cold stress. For this purpose, after soybean (Glycine max) was hydroponically grown for 3 weeks, seedlings were treated with gallic acid (GLA; 1 and 2 mM) and cold stress (5ºC and 10ºC) and GLA and stress combination for 72 h. The inhibition in growth, water content (RWC),osmotic potential (YÕ) and photosynthetic activity observed under stress and was more at the lowest temperature. Stress also elicited the accumulation of proline (Pro) only at 5ºC. While the capacity to maintain high growth, RWC, YÕand photosynthetic efficiency was observed in GLA-treated plants under stress, Pro accumulation could not achieve with GLA plus stress. Any increase in total activities of superoxide dismutase (SOD) and catalase (CAT) induced by stress treatments determined. The lower cold stress caused an increase in the activities of ascorbate peroxidase (APX), glutathione reductase (GR) and NADPH oxidase (NOX). GLA treatment under stress (especially at 5ºC) could supply the increased activities of SOD, CAT, APX and GR. Also, exogenous GLA application to stress-treated plants increased the enzyme activities in ascorbate-glutathione cycle such as monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) and, contents of ascorbate (AsA) and glutathione. After GLA application under stress, it is observed reduction in hydrogen peroxide (H2O2) and the levels of lipid peroxidation (TBARS), and induction of hydroxyl radical (OH●) scavenging. Our results suggest that GLA is a potent inducer for induction of the scavenging activity of radicals as well as effectively usage of water status and photosynthetic capacity. <![CDATA[<b>Grapevine nutritional status and K concentration of must under future expected climatic conditions texturally different soils</b>]]> Nutrition is a relevant issue for winegrowers because it influences grapevine growth, berry composition, as well as must and wine quality. In this research, the following impacts on the nutritional status of cv. Tempranillo grapevines were evaluated: simulated 2100 expected CO2, temperature (T) and relative humidity (RH) conditions (FCC; 700 µmol CO2/mol air, 28/18°C day/night and 33/53% RH, day/night) vs. current CO2, T and RH conditions (Curr; 390 µmol CO2/mol air, 24/14°C and 45/65% RH); well-watered (WW) vs. future expected water deficit (WD); and three texturally different soils with different clay contents (41, 19 and 8%). FCC resulted in reduced concentrations in leaf blades of N and Ca at veraison and N and Zn at full maturity. WD resulted in higher leaf blade Na and Mn concentrations at veraison and maturity, respectively compared to WW. However, K concentrations in the leaves and must were higher for WW than WD. Higher concentrations of Ca and Mn were found in leaf blades of grapevines sampled at full maturity from more clayey soils. Even when nutrient inputs exceeded plant extractions, high soil clay content increased the K concentration in must and consequently, could affect wine quality in terms of acidity loss. However, future expected water stress will have the opposite effect, reducing the berry K uptake under high soil clay (41%) conditions. <![CDATA[<b>Potash use in aerobic production system for basmati rice may expand its adaptability as an alternative to flooded rice production system</b>]]> Direct seeded aerobic rice system has been developed and adopted as an alternative for medium-grain rice in many parts of the world, whereas efforts for aerobic basmati rice types are still in infancy. Among two major constraints for aerobic rice, weeds are progressively being eliminated to great extent through introduction of new herbicides; however, the issue of unfilled grains is still elusive. As potassium (K) deficiency produce sterile pollens in different crops, therefore possible K deficiency in aerobic rice production system may increase unfilled grains in rice. Therefore, it was hypothesized that K application may yield better by improving grain filling of basmati rice, especially, under aerobic conditions. Pot and field experiments were comprised of no K as control, K fertilization using 90 and 180 kg ha-1 keeping recommended N, P and Zn fertilization at the rate of 180, 125 and 25 kg ha-1. Two fine grain rice cultivars Basmati-515 and Super basmati were used due to their differential response to K fertilization. Results indicated that application of 180 kg K2O ha-1 significantly increased the K concentration in shoot, which increased the paddy yield. Highest chlorophyll contents were observed for Basmati-515 in aerobic rice and for Super basmati under flooded condition at 180 kg K2O ha-1. Decrease in number of un-filled grains may a contributory to paddy yield improvement in K fertilized treatments. The improvement in yield was more pronounced in Basmati-515 than Super basmati. Economic analysis showed higher benefit cost ratio for Basmati-515 with 90 kg K2O5 ha-1 under aerobic conditions. Net benefit of K fertilization was increased for both fertilizer rates and both cultivars except 180 kg K ha-1 in Super basmati. As K fertilization increased the number of filled grains and improved the rice yield, therefore it is suggested to apply K fertilizers for better yield and expanded adaptability of aerobic rice production system for basmati rice. Availability of indigenous soil K under aerobic and flooded conditions should be quantified to develop precise K recommendations for both production systems of basmati rice. <![CDATA[<b>Impact of soils and cropping systems on mineral composition of dry cacao beans</b>]]> In view of its high economic value, cacao (Theobroma cacao L.) scientists are seeking technological innovations that increases production and improve quality of cacao beans. The objective of this study was to characterize the mineral (N, K, P, Ca, Mg, Si, Fe, Mn, Zn, Cu, Cd, Ba) composition of cacao beans of clone PH-16 grown in different soil types (Argisols, Cambisols and Latosols) and cropping systems (Cacao Cabruca, Cacao x Erythrina and Cacao x Rubber). With the exception of nitrogen, K was the mineral element most accumulated by cacao beans of PH-16 clone. Potassium, Ca, P and Mg mineral content of dry cacao beans were positively correlated with each other and showed similarity in clusters of average contents in relationship to the different cropping sites. Silicon content in cacao beans is proportionately close to the content of macronutrients. Variations in the content of Mn, Fe, Zn, Cu, Cd and Ba in cacao beans were related to the cropping sites because these mineral elements did not show any significant correlations with each other. Barium contents observed in this study correspond to levels of other micronutrients. In four sites, Cd content was higher than the limit set by the European Union. <![CDATA[<b>Effect of copper (II) ions on morpho-physiological and biochemical variables in <i>Colobanthus quitensis</i></b>]]> Colobanthus quitensisis a species with a wide geographical distribution, including Antarctica. This species must endure a series of limiting abiotic factors in its habitats, such as, high metal ion concentrations. It has been described to inhabit areas where only metal-tolerant species can live. Therefore, it is postulated that the study of this species may provide information about copper tolerance mechanisms. We evaluated the effect of copper (II) ions (control, 100 and 500 µM) on C. quitensis seedlings in vitro, determining morpho-physiological and biochemical variables. Copper showed a significantly negative effect on the development of new shoots (500 µM) and floral apex appearance (100 µM). The analyzed Cu concentrations significantly affected leaf and root length and induced a significant increase in guaiacol peroxidase (G-POD) enzyme activity. The highest proline accumulation took place in seedlings subjected to 500 µM. Furthermore, this concentration induced a significant reduction in chlorophyll a content and exhibited oxidative stress evaluated through an increase in malondialdehyde levels. This is the first study to demonstrate evidence of copper effects on morphological, physiological and biochemical variables in C. quitensis. <![CDATA[<b>Boron toxicity effects on grafted and non-grafted pepper (<i>Capsicum annuum</i>) plants</b>]]> Grafting is a vegetative plant propagation technique. In a grafted plant, the upward supply of water and mineral nutrients as well as the downward flow of photosynthesis are modified. In this context, the objectives of this work were to find out whether the grafting of pepper plants (Capsicum annuum L. family Solanaceae) reduces leaf boron concentration of some commercial cultivars under boron toxicity and to examine the effects of grafting and scion-cultivars on the levels of phenols, flavonoids and antioxidant capacity. Ungrafted plants of the cultivars Century, Twingo, Imperial and Arlequin, as well as grafted Twingo, Imperial and Arlequin plants as scions, and Century as rootstock were used. The plants were treated with 5 mg L-1 boron for 7, 14, 21 and 28 days. After 21 and 28 days of treatment, grafting significantly reduced the boron concentration in the leaves of the scion-cultivars while it was increased by 80% in the non-grafted plants. After 21 days of boron treatment, it was found that grafting reduced the concentration of leaf phenol to 60-70% in ungrafted Century plants. In Century x Twingo there was a 33% increase in the flavonoid concentration of leaves after 7 days grafting; while in the Century x Imperial and Century x Arlequin combinations this was decreased by 75-92% compared to non-grafted Century plants. The antioxidant capacity of leaves after 21 days treatment increased in all rootstock-scion combinations by 28% as measured by the FRAP and DPPH methods. In conclusion, grafting reduced boron concentration in the leaves of the tested scion-cultivars, as well as having an effect on the phenol and flavonoid concentrations and antioxidant capacity of the leaves. <![CDATA[<b>Improving grain yield and water use efficiency of winter wheat through a combination of manure and chemical nitrogen fertilizer on the Loess plateau, China</b>]]> Developing an effective fertilization management practice is crucial for ensuring food security in dryland. A 3-year field experiment was conducted on the Loess plateau dryland, China, to investigate the effects of manure and nitrogen (N) fertilization on soil water regime, grain yield, and water use efficiency (WUE) of winter wheat (Triticum aestivum). The results showed that soil water content at winter wheat sowing was 13.4 mm (3.7%) higher with manure than without after 2 years of fertilization. Additional manure increased soil water recharge, grain yield, and WUE by a mean of 20.7%, 11.6% and 12.6%, respectively, relative to those without manure. Compared with applying manure alone, N fertilization improved soil water recharge, grain yield and WUE by a mean of 56.3%, 11.5%, and 7.0%, respectively. However, no further increases were observed when the N rate exceeded 75 or 150 kg N ha-1, and combining 78 kg N ha-1 fertilizer with manure is sufficient to get 95% of the theoretical highest yield. Therefore, combining manure (30 t ha-1 poultry or pig manure) with 78-150 kg N ha-1 chemical N fertilizer (manure-N : chemical-N =1:0.47-0.91) is recommended for achieving the sustainable winter wheat farming system on the Loess plateau. <![CDATA[<b>Antifeedant effects of common terpenes from Mediterranean aromatic plants on <i>Leptinotarsa decemlineata</i></b>]]> Essential oil terpenes are secondary metabolites produced in different biological pathways as pollinator attraction signals, but also as defense mechanisms against insect pests, herbivores, microorganisms, competing plants, etc. In this context, we have evaluated a total of 24 terpenes commonly found in Mediterranean aromatic plants, including 8 monoterpene hydrocarbons, 9 oxygenated monoterpenes, 2 esterified monoterpenes, 3 sesquiterpene hydrocarbons and 2 oxygenated sesquiterpenes in order to determine their antifeedant effects on the Colorado potato beetle (Leptinotarsa decemlineata Say), a major pest of potato crops. Terpene hydrocarbons showed low antifeedant activity, whereas the oxygenated sesquiterpene (-)-α-bisabolol with an inhibition activity of 96.3% was the most active, followed by carvacrol (90.9%), (+)-Terpinen-4-ol (87.1%) and thymol (81.5%). Other terpenes like (1S)-(-)-verbenone (72.9%), (+/-)-camphor (63.4%) and linalyl acetate (60.7%) showed moderate activity. Subsequently, terpenes showing antifeedant activity against this insect were also tested in allelopathic assays to determine potential damage to the crops. Results showed phytotoxic effects for (1S)-(-)-verbenone on Lactuca sativa germination, and for carvacrol on both the seed germination and the leaf and root growth of Lolium perenne. In conclusion, (-)-α-bisabolol is the best option to develop natural antifeedant formulations against L. decemlineata on the basis of its high antifeedant and low phytotoxic activities. <![CDATA[<b>Characterization of soil fertility using the Rasch model</b>]]> A quantification of the overall soil fertililty potential should integrate the main soil physical and chemical properties, with different units. The formulation of the Rasch model is proposed as an instrument to measure soil fertility potential, integrating 11 soil properties (clay, silt and sand content, organic matter -OM-, pH, total nitrogen -TN-, available phosphorus -AP- and potassium -AK-, cation exchange capacity -CEC-, and deep -ECd- and shallow -ECs- soil apparent electrical conductivity, 0-90 and 0-30 cm depth respectively) measured at 70 locations in a field. In the case study, the considered soil variables fit the model reasonably, having an important influence on soil fertility, except pH, probably due to its homogeneity in the field. Moreover, a ranking of all soil samples according to their fertility potential and the influence of each variable on soil fertility are provided, being ECd, ECs, and the textural fractions of soil the most influential properties on soil fertility and, on the other hand, AP and AK the less influential properties. Results are in accordance with a previous work in the same field considering only five soil properties, both ECd and ECs and texture, denoting the importance of these variables to estimate soil fertility potential. Rasch model resulted to be useful to rationally determine locations in a field where high soil fertility potential exists and establishing those soil samples or properties with anomalies. This information can be necessary to conduct site-specific treatments, leading to a more cost-effective and sustainable field management. <![CDATA[<b>Impact of <i>Pseudomonas aeruginosa</i> MAJ PIA03 affecting the growth and phytonutrient production of castor, a primary host-plant of <i>Samia ricini</i></b>]]> Castor (Ricinus communis L.) is a primary food plant of eri silkworm, Samia ricini Donovan endemic to Northeast India. Plant growth promoting rhizobacteria (PGPR) plays crucial role in growth and productivity of agricultural crops. Eighty-five Pseudomonas strains were isolated from thirty rhizosphere soil samples of castor and their in vitro potentiality was screened for growth promoting ability and antifungal potentialities. Most of the selected Pseudomonas sp. produced indole acetic acid, gibberellic acid, ACC deaminase activity, ammonia, hydrogen cyanide and siderophore, when tested in-vitro for PGP activity. Besides, the strains MAJ PIA01, MAJ PIA03 and MAJ PIA24 have got antifungal activity against five common plant pathogens. Upon their formulation and application in field by curtailing the recommended dose of inorganic fertilizers to 50 %, isolate no. MAJ PIA03 efficiently enhanced the agronomical traits such as number of leaves per plant, leaf biomass, root length, stem base diameter, shoot length, root biomass and leaf moisture content. Isolate no. MAJ PIA03 has significant impact on leaf biochemical constituents and augments the nutritional quality of castor leaf. The most efficient isolate MAJ PIA03 was identified as Pseudomonas aeruginosa MAJ PIA03 by polyphasic approach and its 16S rRNA gene homology. The bio-formulation of Pseudomonas aeruginosa MAJ PIA03 with 50 % diminution on recommended inorganic NPK dose could be used as an effective mechanism to improve Ricinus communis plant growth as well as leaf nutritional enhancement for sustainable eri sericulture. <![CDATA[Effects of biochar application on nitrogen leaching, ammonia volatilization and nitrogen use efficiency in two distinct soils]]> This study was conducted to determine the effect of biochar application on nitrogen (N) leaching, ammonia (NH3) volatilization, and fertilizer N use efficiency (NUE) in two soils with different properties (loamy and sandy). Ryegrass (Lolium perenne L.) incubation experiments (with 15N-enriched urea applied) and an N loss simulation study were conducted at biochar application rates of 2% and 4%. The results showed that 15N utilization increasedby 8.83-9.06% following the addition of biochar to sandy soil during the first season compared with the control. However, this significant effect was not observed in the loamy soil, in which significantly more urea-N was retained in the soil following biochar application. Furthermore, based on the results of the N leaching and NH3 volatilization experiments, 29.19% and 28.65% NO3-N leaching reductions were induced by 2% and 4% biochar amendments in loamy soil, decreasing the total inorganic N that was leached (NH4+-N plus NO3-N) by 26.46% and 26.82%, respectively. However, although the amount of leached NH4+-N decreased in biochar-amended sandy soil, the cumulative NH3 volatilizations were 14.18-20.05% higher than in the control, and 22.55% more NO3--N was leached from biochar-amended sandy soil, resulting in a negative effect on N retention. According to this study, biochar can be effectively used to improve the NUE in sandy soil and reduce N loss from loamy soil. <![CDATA[<b>Anaerobic degradation of municipal organic waste among others composting techniques improves N cycling through waste-soil-plant continuum</b>]]> This study aimed to examine the effect of composting techniques of municipal organic solid waste (MSW) for (i) total carbon (C), nitrogen (N) losses, and changes in its chemical characteristics during composting phase and (ii) value of the composted materials as fertilizer when applied to vegetables. Treatments included: aerobic composting (AC), anaerobic composting (ANC), co-composting (CC) and open dumping (OD) for 4 months. During the composting phase, about 61, 50, 35, and 13% of the initial N was lost from CC, AC, OD, and ANC, respectively. The respective values in case of total C loss were 17, 13, 14 and 11%. After field application, about 41% of the applied organic N was mineralized from ANC material, whereas the respective values for OD, CC and AC were 25-26, 15-16, and 12-19%. Consequently, dry matter (DM) yield and vegetable N uptake from the resultant compost were in the order ANC>OD>CC>AC. Moreover, vegetable apparent N recovery (ANRf) was the highest from ANC (spinach: 36 and carrot: 45%) followed by OD (26 and 34%), CC (18 and 26%) and AC (18 and 24%) material. When composting N losses were taken into account during calculations, about 31-39, 17-22, 9-10, and 7-12% of the N collected from filth depots ended up in plants from ANC, OD, CC and AC, respectively. We concluded that ANC results in least C and N losses during the composting phase and greatest N mineralization in the soil, which enhances vegetable yield, N recovery and thereby the N cycling through waste-soil-plant continuum. <![CDATA[<strong>Land use conversion in humid tropics influences soil carbon stocks and forms</strong>]]> Land use change is one of the most important drivers of excessive carbon dioxide (CO2) emission and is partly responsible for global warming. Certain land use systems promote the sequestering of excessive carbon from the atmosphere to the soil, while other systems accelerate C loss through emissions. Herein, a study was conducted to evaluate the soil C forms and carbon stocks in the soils of three land use systems (a pasture, field crop and cocoa plantation) that were developed following the conversion of grasslands in the humid lowland landscape of Papua New Guinea. A remarkable decline (P<0.001) in the total C concentration of the grassland soils was observed due to land conversion into either field crops (44%) or a cocoa plantation (28%). Among the land use systems, organic C was the dominant pool (78.1-86.9%) compared to inorganic C, which only contributed 13.1%-21.9% to the total C stock. The soil organic C stocks were present in the following order: grassland (217.9 Mg ha-1) &gt; pasture (207.6 Mg ha-1) &gt; cocoa plantation (139.4 Mg ha-1) &gt; field crops (131.6 Mg ha-1). The results of this study indicated that the conversion of grasslands to other land use systems (such as a cocoa plantation and field crops) could lead to the depletion of soil C stocks.