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Soil heavy metal pollution is becoming more and more serious. Biomass charcoal application can play an important role in alleviating the toxicity of heavy metals in soils. Compared with other biochar, bamboo charcoal has more unique properties and may have a unique effect on heavy metal pollution. Zhejiang Province of Southeastern China is rich in bamboo resources. However, few studies related to bamboo charcoal application for heavy metal remediation in farmland were reported. In this study, four treatments with different amounts of bamboo charcoal application were set up through a field experiment, namely BC0 (no bamboo charcoal application), BC1 (2500 kg⋅ha-1), BC2 (5000 kg⋅ha-1), and BC3 (10000 kg⋅ha-1), and each treatment was replicated three times. The results showed that (1) The application of bamboo charcoal significantly increased the soil pH and organic matter content. Compared with BC0, the pH and organic content of BC3 increased by 7.4% and 17.4% (P < 0.05) respectively. (2) The HCl-extractable Cd content of paddy soil in the BC1 treatment was significantly lower than other treatments (P < 0.05), and decreased by 15.3%, compared with BC0. The soil HCl-extractable Zn and Cu content did not differ significantly between treatments (P > 0.05). (3) With the increase of bamboo charcoal application, the Cd content in rice gradually decreased, the BC3 treatment significantly decreased by 39.0% (P < 0.05), and the Zn and Cu contents in rice did not differ significantly between treatments (P > 0.05), compared with BC0. (4) Soil pH, organic matter and Cd in rice seeds were significantly negatively correlated (P < 0.01). The heavy metal content in rice does not change with the change of heavy metal content with HCl-extractable state in soil. It means bamboo charcoal does not reduce heavy metal content in rice by simply declining the heavy metal content with HCl-extractable state. The mechanism of action is relatively complicated, and further study is needed. [ABSTRACT FROM AUTHOR]

Potassium (K) is an essential plant nutrient mainly present in the crystal structure of K-bearing soil minerals (K-feldspars, micas). To assess the evolution of (clay) mineralogy due to K+ release from these minerals in continuously cultivated soils, s amples were collected from long-term (1904–2014) field experiments submitted to contrasting crop rotations and amendments, with and without fertilisation. Soil samples were size-fractionated and mineralogy of the silt fraction and of clay subfractions was determined quantitatively by modelling X-ray diffraction (XRD) patterns. Clay subfractions were also analysed for their cation exchange capacity (CEC). Mineralogical data indicate the stability of clay mineralogy and the increased abundance of the finest clay subfraction at the expense of coarser ones, regardless of agronomic practices or amount of K removed by plants. This increase is accompanied by an increase in the bulk clay CEC owing to the major contribution of the finest clay subfraction to this parameter. Mineral dissolution, rather than alteration of mineral phases from coarse clay subfractions, most likely supplements K for plant nutrition in this soil. Dissolution is favoured over cation exchange owing to the dioctahedral character of micas and to their fine-grained granulometry. The observed long-term mineralogical resilience also indicates that part of plant nutrition is obtained from subsoil in a non K-limited context, whereas K supply through K-feldspar dissolution appears marginal. Unlabelled Image • Evolution of clay mineralogy was quantified in long-term experimental plots. • Different agronomical practices lead to contrasting K balances. • Clay mineralogy is stable over time in all subplots independent of K balance. • K is supplied by the dissolution of illite-rich coarse clay fractions and by subsoil. • Dioctahedral character of fined-grained micas favours dissolution over K-exchange. [ABSTRACT FROM AUTHOR]

Fine‐root traits show remarkable variation with plant community structure and environmental shifts, but there is limited understanding of how trait covariation that exists among fine‐root traits shifts among different communities, especially in forests. We explored links among the fine‐root traits of forest communities to determine whether community root traits shift predictably according to an economics framework along environmental gradients.Measurements of root morphology, nitrogen, phosphorus and carbon concentrations, and measures of standing root densities were collected on fine‐roots (diameter ≤ 2 mm) from 129 forest plots in five subalpine forests.This study demonstrates an existence of a community‐level fine‐root economics spectrum (REScom) in the subalpine forests, in which specific root length was strongly and positively related to root nitrogen and phosphorus contents, but negatively related to root diameter. Soil nutrient limitation was a major driver of the REScom as changes in soil [N], [P] and [C] contents were related to changes in SRL, root [N], root [P]. Variables related to standing fine‐root length and mass were independent of the REScom and were primarily related to forest community structure, particularly in tree closure and herbaceous plant mass.Synthesis. These results indicate two distinct functional dimensions of community fine‐root trait variation: resource‐use efficiency via changes in root structure and construction, and separately via changes in the standing root system. Identifying shifts in allocation to and investment in fine‐roots enhances our understanding of a root and whole‐plant economics spectrum and community functioning. [ABSTRACT FROM AUTHOR]

The role of mycorrhizal symbiosis as a control of the biogeochemical cycle of nitrogen in soils and in the nitrogen nutrition of plants is considered. The contribution of ericoid mycorrhiza (ErM) and ectomycorrhiza (EcM) to nitrogen (N) supply of host plants is well known, whereas the role of arbuscular mycorrhiza (ArM) is insufficiently understood. Exoenzymes released into the soil from the ErM and EcM mycelium favor the hydrolysis of high-molecular-weight N-containing organic compounds of plant litter and soils to or amino acids that are then transported toward plant roots and are absorbed by them. ArM-producing fungi have a limited capacity to release hydrolytic enzymes capable to decompose high-molecular-weight organic compounds into the soil (or do not have it at all). Therefore, they are specialized on the absorption of inorganic forms of N and amino acids appearing in the soil in the course of decomposition of high-molecular-weight N-containing compounds by saprotrophic microorganisms. The activity of hydrolytic exoenzymes and the role of mycorrhiza in the nitrogen nutrition of plants become more significant under conditions of the low supply with mineral N compounds and decrease upon the rise in availability of mineral N compounds. At the same time, mycorrhizal fungi and host plants may compete for the limited resource. The isotopic composition of N in plants (δ15N) and the fractionation of 15N isotope between the mycorrhizal fungi and host plants are considered indicative of the participation of mycorrhiza in the nitrogen nutrition of plants. [ABSTRACT FROM AUTHOR]

Highlights • SWAT application for modeling the soil nutrient change in an arid plain region. • Soil available phosphorus surplus for intense cropland was estimated by SWAT model. • Available phosphorus surplus was mainly due to low fertilizer recovery efficiency. • Soil available phosphorus surplus would reduce along with precipitation increase. • Soil available phosphorus accumulation increased groundwater pollution risk. Abstract The excessive application of phosphorus fertilizer has caused available phosphorus (AP) surplus in cultivated soils. By using the Soil and Water Assessment Tool (SWAT), the soil AP surplus and its relationship with fertilization and environmental changes was estimated for the wheat-maize rotation production area in the Baiyangdian basin, which is a typical arid region in North China Plain. Due to the little runoff, the model was validated by the measured AP concentration in deep soil profiles of the cropland. The results indicated that with an evident overuse of phosphorus fertilizer, the average rate of AP surplus in soils in the basin was about 10.3% of the applied fertilizer. A large part of the applied phosphorus (57.2%) was accumulated in active mineral forms. The phosphorus fertilizer recovery efficiency averaged 41.4%, ranging between 29.3% and 51.7%. This lower efficiency was expected to be the main reason for the serious AP surplus in cultivated soils. As a result, it was predicted that for every 100 kg ha−1 of P fertilizer added, the AP of the plough layer (0–20 cm) will be increased by an average of 3.35 mg kg−1 (around 10 kg P ha−1) in the study area. Furthermore, the soil AP surplus was predicted to reach a higher level under the condition of lower precipitation because of less runoff-induced erosion and leaching to deeper layers. From 1993–2010, the soil AP accumulation was 445.7 kg ha−1 in the study area, with an average accumulation rate of 24.8 kg ha−1yr−1, which belongs to the highest level worldwide. Through combining the measured data with the simulated results, it was suggested that excessive phosphorus fertilizer application along with low phosphorus fertilizer recovery efficiency will increase the risk of P leaching, which threatens the security of groundwater. [ABSTRACT FROM AUTHOR]

Unconventional soil cultivation and its different variants used in some Romanian farms are preferred due to their cultivation technology and economic advantages, as well as to their compatibility with the Common Agricultural Policy. The option for unconventional systems depends on the system of agricultural machines and on the physical soil features, particularly clay content and compaction degree. Unconventional systems need knowledge of technological crop requirements as well as of the way fertilisation can be adapted and weeds can be controlled. Unconventional systems influence both soil features and energy inputs. Benefits of applying unconventional systems are:Soil cultivation time is reduced 2-4 times; Fuel consumption per area unit is reduced with 30-50%;The number of agricultural machines per area unit is reduced;Soil structure and surface and depth soil compaction are recovered; Organic matter in the soil increases;Water permeability in the soil increases and global soil drainage improves;Soil erosion is reduced;Plant debris on soil surface or incorporated in the soil (10-15 cm deep, where biological activity is maximum) contribute to soil flora and fauna growth;Ground and surface water quality is maintained (nutrients and pesticides are no longer washed away by erosion and more intense biological activity - associated to soil organic matter - uses and decomposes the nutrients);Air quality is maintained by reducing fossil fuel emissions (Diesel) used in the field and by reducing the carbon released in the atmosphere (it is fixed by soil organic matter increase). Humus content in the soil tends to increase with minimum soil tillage. This is partly due to larger amounts of plant debris (minimum 30%) at different decomposition stages when left on soil surface and in the first 10-20 cm and, on the other hand, to the balance between mineralisation and humidification achieved by specific physical, thermal, and biological regimes. Measuring humus content after 4 years shows an increasing trend of up to 0.41%. The values reached 3.11% in the ploughed variant and 3.12-3.52% in the minimum tillage variants. [ABSTRACT FROM AUTHOR]

The current study describes quantitatively the interactions between (a) activity of extracellular enzymes: β‐glucosidase (BG), protease (Prot), alkaline phosphatase (Alk P), and acid phosphatase (Acid P); (b) intracellular activities: respiration, dehydrogenase activity (DHA); and (c) C and N contents of soil: Corg—organic carbon, Cmic—microbial biomass, ratio Cmic:Corg, Ntot—total nitrogen, and ratio C:N in earthworm‐affected and surrounding loess soil under a pear orchard. The soil tested was collected from: burrow walls (0–3 mm) and a transition zone (3–7 mm) both forming drilosphere, bulk soil (20 mm from the burrow wall), and cast aggregates. The enzyme activities were presented as total 'tot' (per gram of dry soil mass) and specific 'spec' (per Cmic). It was shown that soil Cmic, basal respiration, BGtot, Prottot, and Alk Ptot were significantly positively correlated with Corg, Cmic:Corg, Ntot, and C:N (r = 0.627–0.976). However, the specific BGspec, Protspec, and Acid Pspec were negatively correlated, while specific respiration (qCO2) and Alk Pspec were not correlated with most soil characteristics. The relationships between DHAtot, DHAspec, and all soil characteristics were positive and had the highest correlation coefficients (r = 0.703–0.989). Response ratio of the enzyme activity was more strongly affected by enzyme activity location (extracellular vs. intracellular) and presentation method (total vs. specific), than by earthworm‐affected soil compartments. The results suggest a need to consider the method of enzyme activity presentation (specific vs. total) that supports understanding ecologically relevant microbial processes in earthworm‐inhabited orchard soils. [ABSTRACT FROM AUTHOR]

Although numerous studies suggest that organic amendments are better at maintaining soil fertility and crop production than mineral-only fertilization, it is unclear if this occurs in different agricultural systems on a global scale. Here we report a comprehensive meta-analysis of 690 independent experiments comparing the performance of organic amendments and mineral-only fertilization on crop yields, the soil organic carbon (SOC) and total nitrogen (TN) contents, soil nutrient dynamics and biological properties. Our analysis shows that organic amendments increased crop yields on average of 27% than mineral-only fertilization. Farmyard manure (FYM) had the highest effect (49% increase) and this was especially clear in wheat croplands (40% increase). Organic amendment increased the amount of SOC (38%), TN (20%), microbial biomass carbon (MBC; 51%) and microbial biomass nitrogen (MBN; 24%) than mineral-only fertilization. Organic amendments also increased the soil microbiome enzyme activity in terms of soil hydrolytic C acquisition (C-acq; 39%), N acquisition (N-acq; 22%), P acquisition (P-acq; 48%) and oxidative decomposition (OX; 58%). Increased nutrient acquisition and oxidative decomposition could explain the positive effects of organic amendment on crop yields. These observed patterns were consistent for most organic amendments and cropping systems in diverse regions of the world. In summary, our analysis suggests that organic amendments can improve microbe-mediated soil ecosystem functioning, long-term soil fertility and crop productivity, relative to mineral fertilization, on a global scale. [ABSTRACT FROM AUTHOR]

In the present study to investigate the physico-chemical properties of Onion and Tomato soil at ten different sites of Junnar tehsil of Pune District. The soil parameters like soil pH, EC, Organic Carbon, Nitrogen, Potassium and Phosphorous content were analyzed. It was found that there was a marked variation in nutrients and parameters of various sample point in different farmers field. The results of the study show the low levels of Nitrogen, Phosphorous and Potassium in both sites. Also the organic matter is low during the study area. [ABSTRACT FROM AUTHOR]

A participatory program was conducted in western Iran to calculate nutrient balances. Information on farmer's resources and soil characteristics were collected in two watersheds (Honam and Merek). Results showed a positive and negative balance for some crops in two studied areas. [ABSTRACT FROM AUTHOR]

The movement of excess phosphorus (P) into streams, rivers, and lakes poses a significant threat to water quality and the health of aquatic ecosystems and thus, P has been targeted for reduction. In landscapes dominated by agriculture, P is primarily transported through non-point sources, which a number of best management practices aim to target. One such practice is vegetated buffer strips (VBS), which are designed to use dense vegetation above the surface and extensive root systems below the surface to reduce runoff velocity, trap sediments, increase infiltration, and increase plant uptake of nutrients. The effectiveness of VBS in reducing P concentrations has been studied and reviewed, but most studies have been undertaken in warm or temperate climates, where runoff is primarily driven through summer rainfall events and when vegetation is actively growing. In cold climates, the majority of runoff occurs during the snowmelt period, when soils are frozen and vegetation has been flattened by snow and ice over the winter period and is not actively taking up nutrients. These conditions hinder the ability of VBS to work as designed. Additionally, frozen vegetation can release P after undergoing freeze–thaw cycles (FTCs). Thus, this review aimed to (i) summarize research designed to determine the effectiveness of VBS in reducing P transport in cold climates, (ii) collate research on the potential for vegetation to release P after undergoing FTCs, and (iii) identify research gaps to be addressed in determining VBS effectiveness in cold climates. Cold-climate VBS implemented in Canada, the northern United States, and northern Europe have shown P removal efficiencies ranging from −36% to +89%, a range that identifies the uncertainty surrounding the use of VBS in these landscapes. However, there is consensus among researchers globally that vegetation does release P after undergoing FTCs, though P concentrations from different species vary across studies. The design and management of VBS in cold climates requires careful consideration, and VBS may not always be the best management strategy to reduce P transport. Future research should be undertaken at a larger scale in natural systems and focus on VBS design and management strategies. [ABSTRACT FROM AUTHOR]

Abstract. The newly circumscribed group Palicourea Aubl. sect. Egenses C. M. Taylor includes 13 species found in South America in the Amazon and Orinoco basins, the Guayana Highlands, northwestern Venezuela, and the central Andes, often on nutrient-poor (oligotrophic) soils, and is diagnosed by features of its leaves, inflorescences, and fruits. Its species are separated mainly by details of stipules, inflorescence arrangement, bracts, and flower and fruit size, as outlined in a key, and have different ranges and some unusual morphological features as detailed for each. Newly published here are the combination P. moyobambana (Standl.) C. M. Taylor, the new species P. articulata C. M. Taylor from southeastern Colombia and P. flagellifera C. M. Taylor from Amazonian Colombia, and the new subspecies P. egensis subsp. zuliana C. M. Taylor from northwestern Venezuela. [ABSTRACT FROM AUTHOR]

Two vermicompost treatments providing 45 (V1) and 90 (V2) kg P ha−1 and mycorrhizae (M) inoculation were evaluated alone and in combinations for wheat (Triticum aestivum L.) growth and soil fertility status. The treatments included; the Control, nitrogen (N): dipotassium oxide (K2O) as basal dose (BD; 120:60 kg ha−1), N: phosphorus pentoxide (P2O5): K2O as recommended dose (RD; 120:90:60 kg ha−1), BD+Myccorhiza (BDM), BD+V1 (BDV1), BDM+V1 (BDMV1), BD+V2 (BDV2), and BDM+V2 (BDMV2). Combination of mycorrhizae and vermicompost (BDMV1 and BDMV2) significantly and maximally improved the growth, plant N, phosphorus (P), and micronutrient concentrations over the control, reduced the soil pH by 5 and 6%, increased OM by 25 and 112%, total N by 41%, and extractable P up to 200% while the extent of improvement was directly related to the content of added vermicompost. Results indicated that vermicompost at either level synergistically affected the mycorrhizae in plant nutrition as well as improved soil fertility status and soil chemical properties. [ABSTRACT FROM AUTHOR]

Soil and nutrient loss is a common natural phenomenon but it exhibits unclear understanding especially on bare loess soil with variable rainfall intensity and slope gradient, which makes it difficult to design control measures for agricultural diffuse pollution. We employ 30 artificial simulated rainfalls (six rainfall intensities and five slope gradients) to quantify the coupling loss correlation of runoff-sediment-adsorbed and dissolved nitrogen and phosphorus on bare loess slope. Here, we show that effects of rainfall intensity on runoff yield was stronger than slope gradient with prolongation of rainfall duration, and the effect of slope gradient on runoff yield reduced gradually with increased rainfall intensity. But the magnitude of initial sediment yield increased significantly from an average value of 6.98 g at 5° to 36.08 g at 25° with increased slope gradient. The main factor of sediment yield would be changed alternately with the dual increase of slope gradient and rainfall intensity. Dissolved total nitrogen (TN) and dissolved total phosphorus (TP) concentrations both showed significant fluctuations with rainfall intensity and slope gradient, and dissolved TP concentration was far less than dissolved TN. Under the double influences of rainfall intensity and slope gradient, adsorbed TN concentration accounted for 7-82% of TN loss concentration with an average of 58.6% which was the main loss form of soil nitrogen, adsorbed TP concentration accounted for 91.8-98.7% of TP loss concentration with an average of 96.6% which was also the predominant loss pathway of soil phosphorus. Nitrate nitrogen (NO3−-N) accounted for 14.59-73.92% of dissolved TN loss, and ammonia nitrogen (NH4+-N) accounted for 1.48-18.03%. NO3−-N was the main loss pattern of TN in runoff. Correlation between dissolved TN, runoff yield, and rainfall intensity was obvious, and a significant correlation was also found between adsorbed TP, sediment yield, and slope gradient. Our results provide the underlying insights needed to guide the control of nitrogen and phosphorus loss on loess hills. [ABSTRACT FROM AUTHOR]

Abstract: Plant litter decomposition is key to carbon and nutrient cycling in terrestrial ecosystems. Soil fauna are important litter decomposers, but how their contribution to decomposition changes with alterations in plant composition and climate is not well established. Here, we quantified how soil mesofauna affect decomposition rate interactively with climate and leaf and root traits. We conducted an in situ decomposition experiment using eight dominant tree species per forest site across four elevations (50, 400, 600 and 1,000 m a.s.l.) in northern Japan. We used litterbags with different mesh sizes to control litter accessibility to soil mesofauna. We found stronger effects of plant litter quality on both decomposition rates and faunal contribution thereto, and perhaps of local variation in soil nutritional and moisture regimes, than climatic effects of elevation. This suggests that changing climate likely alters forest litter decomposition rates indirectly through shifts in tree community composition more than directly through changing abiotic regimes. Considering both leaves and roots as litter resources enlarged the overall contribution of variation in litter quality to decomposition rates and faunal effects thereupon, because litter quality and decomposition rate varied more between leaves and roots overall than among leaves within and across elevations. The contribution of mesofauna to litter decomposition was larger in nutrient‐rich litter than in recalcitrant litter across the elevational gradient, suggesting amplification of the effect of litter traits on decomposition through preference of soil fauna for their food resources. Our findings highlight the importance of considering synergistic influences of soil faunal activities with litter traits of both leaves and roots for better understanding biogeochemical processes across environmental gradients over space or time. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

Abstract: Pulse‐type perturbation through excreta by animals creates a mosaic of short‐term high nutrient‐load patches in the soil. How this affects microbial community composition and how long these impacts last are important for microbial community dynamics and nutrient cycling. Our study focused on the short‐term responses to N by bacterial communities and ‘functional groups’ associated with the N cycle in a lowland evergreen tropical rainforest. We applied a single urea pulse, equivalent to urine‐N deposition by medium‐sized mammals to simulate N enrichment and changes in soil N availability, and analysed soil bacterial communities using molecular methods, before and after urea application. Urea addition increased mineral N availability and changed bacterial community composition, from phylum to operational taxonomic unit levels, however, taxon richness and diversity were unaffected. Taxa involved in the physiologically “narrow” processes of nitrification (e.g. Nitrosospira) and denitrification (e.g. Phyllobacteriaceae, Xanthomonadaceae and Comamonadaceae) increased their relative abundance, while N2‐fixers (e.g. Rhodospirillales, and Rhizobiales) decreased after treatment. While a temporal legacy on both community composition and functional group profile was observable 58 and 159 days after treatment, at the latter date bacterial communities were already tending towards pre‐treatment composition. We suggest that pulse‐type perturbation by mammal urine that occurs on a daily basis has strong short‐term effects on patch dynamics of soil microbiota and N availability. Such a spatio‐temporally dynamic soil environment enhances overall microbial richness and diversity, and contributes to the apparent temporal resilience of community composition. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

Increased nutrient cycling in the agri-food system is a way to achieve a healthier nutrient stewardship and more sustainable food production. In life cycle assessment (LCA) studies, use of recycled fertilizer products is often credited by the substitution method, which subtracts the environmental burdens associated with avoided production of mineral fertilizer from the system under study. The environmental benefits from avoided fertilizer production can make an important contribution to the results, but different calculation principles and often implicit assumptions are used to estimate the amount of avoided mineral fertilizer. This may hinder comparisons between studies. The present study therefore examines how the choice of substitution principles influences LCA results. Three different substitution principles, called one-to-one, maintenance, and adjusted maintenance, are identified, and we test the importance of these in a case study on cattle slurry management. We show that the inventory of avoided mineral fertilizer varies greatly when the different principles are applied, with strong influences on two-thirds of LCA impact categories. With the one-to-one principle, there is a risk of systematically over-estimating the environmental benefits from nutrient cycling. In a sensitivity analysis we show that the difference between the principles is closely related to the application rate and levels of residual nutrients in the soil. We recommend that LCA practitioners first and foremost state and justify the substitution method they use, in order to increase transparency and comparability with other studies. [ABSTRACT FROM AUTHOR]

Orchard management practices such as weed control and irrigation are primarily aimed at maximizing fruit yields and economic profits. However, the impact of these practices on soil fertility and soil microbiology is often overlooked. We conducted a two-factor experimental manipulation of weed control by herbicide and trickle irrigation in a nutrient-poor peach ( Prunus persica L. cv. Contender) orchard near Jackson Springs, North Carolina. After three and eight years of treatments, an array of soil fertility parameters were examined, including soil pH, soil N, P and cation nutrients, microbial biomass and respiration, N mineralization, and presence of arbuscular mycorrhizal fungi (AMF). Three general trends emerged: 1) irrigation significantly increased soil microbial biomass and activity, 2) infection rate of mycorrhizal fungi within roots were significantly higher under irrigation than non-irrigation treatments, but no significant difference in the AMF community composition was detected among treatments, 3) weed control through herbicides reduced soil organic matter, microbial biomass and activity, and mineral nutrients, but had no significant impacts on root mycorrhizal infection and AMF communities. Weed-control treatments directly decreased availability of soil nutrients in year 8, especially soil extractable inorganic N. Weed control also appears to have altered the soil nutrients via changes in soil microbes and altered net N mineralization via changes in soil microbial biomass and activity. These results indicate that long-term weed control using herbicides reduces soil fertility through reducing organic C inputs, nutrient retention and soil microbes. Together, these findings highlight the need for alternative practices such as winter legume cover cropping that maintain and/or enhance organic inputs to sustain the soil fertility. [ABSTRACT FROM AUTHOR]

Abstract: Soil fungi and bacteria are the key players in the transformation and processing of carbon and nutrients in terrestrial ecosystems, yet controls on their abundance and activity are not well understood. Based on stoichiometric principles, soil microbial processes are expected to be limited by mineral nutrients, which are particularly scarce in often highly weathered tropical forest soils. Such limitation is directly relevant for the fate of soil carbon and global element cycles, but its extent and nature have never been assessed systematically across the tropical biome. Here, we address the relative importance of nitrogen, phosphorus, and other nutrients in limiting soil microbial biomass and process rates in tropical forests. We conducted an in‐depth literature review and a meta‐analysis of the available nutrient addition experiments in tropical forests worldwide. Our synthesis showed predominant and general phosphorus limitation of a variety of microbial processes across tropical forests, and additional nitrogen limitation in tropical montane forests. The apparent widespread microbial phosphorus limitation needs to be accounted for in the understanding and prediction of biogeochemical cycles in tropical forests and their future functioning. Other mineral nutrients or carbon may modify the importance of phosphorus, but more experimental studies are urgently needed. [ABSTRACT FROM AUTHOR]

Soil microorganisms regulate element cycling and plant nutrition, mediate co-existence of neighbors, and stabilize plant communities. Many of these effects are dependent upon environmental conditions and, in particular, on nutrient quality and availability in soils. In this context, we set up a pot experiment in order to examine the combined effects of soil nutrient availability and microbial communities on plant-soil interactions and to investigate assemblage rules for soil bacterial communities under changed nutrient conditions. Four gamma-sterilized soils, strongly differing in their nutrient contents, were obtained from different fertilization treatments of a centenary field experiment and used to grow communities of grassland plants. The sterilized soils were either self- or cross-inoculated with microbial consortia from the same four soils. Molecular fingerprinting analyses were carried out at several time points in order to identify drivers and underlying processes of microbial community assemblage. We observed that the bacterial communities that developed in the inoculated sterilized soils differed from those in the original soils, displaying dynamic shifts over time. These shifts were illustrated by the appearance of numerous OTUs that had not been detected in the original soils. The community patterns observed in the inoculated treatments suggested that bacterial community assembly was determined by both niche-mediated and stochastic-neutral processes, whereby the relative impacts of these processes changed over the course of the vegetation season. Moreover, our experimental approach allowed us not only to evaluate the effects of soil nutrients on plant performance but also to recognize a negative effect of the microbial community present in the soil that had not been fertilized for more than 100 years on plant biomass. Our findings demonstrate that soil inoculation-based approaches are valid for investigating plant-soil-microbe interactions and for examining rules that shape soil microbial community assemblages under variable ecological conditions. [ABSTRACT FROM AUTHOR]

Whether niche processes, like environmental filtering, or neutral processes, like dispersal limitation, are the primary forces driving community assembly is a central question in ecology. Here, we use a natural experimental system of isolated tree 'islands' to test whether environment or geography primarily structures fungal community composition at fine spatial scales. This system consists of isolated pairs of two distantly related, congeneric pine trees established at varying distances from each other and the forest edge, allowing us to disentangle the effects of geographic distance vs. host and edaphic environment on associated fungal communities. We identified fungal community composition with Illumina sequencing of ITS amplicons, measured all relevant environmental parameters for each tree-including tree age, size and soil chemistry-and calculated geographic distances from each tree to all others and to the nearest forest edge. We applied generalized dissimilarity modelling to test whether total and ectomycorrhizal fungal ( EMF) communities were primarily structured by geographic or environmental filtering. Our results provide strong evidence that as in many other organisms, niche and neutral processes both contribute significantly to turnover in community composition in fungi, but environmental filtering plays the dominant role in structuring both free-living and symbiotic fungal communities at fine spatial scales. In our study system, we found pH and organic matter primarily drive environmental filtering in total soil fungal communities and that pH and cation exchange capacity-and, surprisingly, not host species-were the largest factors affecting EMF community composition. These findings support an emerging paradigm that pH may play a central role in the assembly of all soil-mediated systems. [ABSTRACT FROM AUTHOR]

Herbivores impact nutrient availability and cycling, and the net effect of herbivory on soil nutrients is generally assumed to be positive in nutrient-rich environments and negative in nutrient-poor ones. This is, however, far from a uniform pattern, and there is a recognized need to investigate any interactive effects of herbivory and habitat fertility (i.e., plant C/N ratios) on soil nutrient availabilities. We determined long-term effects of reindeer on soil extractable nitrogen (N) and phosphorus (P) and their net mineralization rates along a fertility gradient of plant carbon (C) to N and P ratios in arctic tundra. Our results showed that reindeer had a positive effect on soil N in the more nutrient-poor sites and a negative effect on soil P in the more nutrient-rich sites, which contrasts from the general consensus. The increase in N availability was linked to a decrease in plant and litter C/N ratios, suggesting that a shift in vegetation composition toward more graminoids favors higher N cycling. Soil P availability was not as closely linked to the vegetation and is likely regulated more by herbivore-induced changes in soil physical and chemical properties. The changes in soil extractable N and P resulted in higher soil N/P ratios, suggesting that reindeer could drive the vegetation toward P-limitation. This research highlights the importance of including both the elements N and P and conducting studies along environmental gradients in order to better understand the interactive effects of herbivory and habitat fertility on nutrient cycling and primary production. [ABSTRACT FROM AUTHOR]

The article offers information on the use of denitrification bioreactors in agricultural water quality protection. Topics discussed include the efforts to improve nutrient management in soils, the goal of reducing nitrogen from soils, and the removal of ammonia from the soils. Also mentioned are the factors affecting bioreactor performance including temperature, hydraulic retention time and woodchip source.

Agricultural soils generally have a low content of organic matter, which affects soil fertility and hence crop yields. The use of olive pomace as an organic amendment could enhance soil properties due to its high content of organic matter and exchangeable cations as well as its extensive availability. However, little is known about the potentially detrimental effects of salts and high content of phenolic substances that might occur over time with the use of pomace amendment in agricultural soils. Similarly, its impact on microbial communities and enzyme activities is largely unknown. To ascertain these effects, we tested the response of soil enzyme activities (β-glucosidase, urease, acid phosphomonoesterase and dehydrogenase) starting from a long-term (8-year) previously amended soil and a control (non-amended) soil and exposing these soils to a short-term (12-week) laboratory experiment. We also focused on soil organic matter and mineral N, on relating enzymatic data to bacterial and fungal biomasses, and on an index for soil functional quality based on enzyme activities (AI3). Our results show that organic matter, enzyme activities and the soil quality index were improved by long-term treatment with olive pomace, contrasting with scant effects from short-term laboratory incubation. In spite of its high content in salts and phenolic substances, no detectable negative impact emerged from the use of this amendment. Overall, olive pomace clearly increased soil organic matter and improved soil biological activity and quality, without any detectable negative effects. [ABSTRACT FROM AUTHOR]

Soil is an important environment for crop growth. Quick and accurately access to soil nutrient content information is a prerequisite for scientific fertilization. In this work, hyperspectral imaging (HSI) technology was applied for the classification of soil types and the measurement of soil total nitrogen (TN) content. A total of 183 soil samples collected from Shangyu City (People's Republic of China), were scanned by a near-infrared hyperspectral imaging system with a wavelength range of 874-1734 nm. The soil samples belonged to three major soil types typical of this area, including paddy soil, red soil and seashore saline soil. The successive projections algorithm (SPA) method was utilized to select effective wavelengths from the full spectrum. Pattern texture features (energy, contrast, homogeneity and entropy) were extracted from the gray-scale images at the effective wavelengths. The support vector machines (SVM) and partial least squares regression (PLSR) methods were used to establish classification and prediction models, respectively. The results showed that by using the combined data sets of effective wavelengths and texture features for modelling an optimal correct classification rate of 91.8%. could be achieved. The soil samples were first classified, then the local models were established for soil TN according to soil types, which achieved better prediction results than the general models. The overall results indicated that hyperspectral imaging technology could be used for soil type classification and soil TN determination, and data fusion combining spectral and image texture information showed advantages for the classification of soil types. [ABSTRACT FROM AUTHOR]

Background: Soil microorganisms play key roles in nutrient cycling and are distributed throughout the soil profile. Currently, there is little information about the characteristics of the microbial communities along the soil depth because most studies focus on microorganisms inhabiting the soil surface. To better understand the functions and composition of microbial communities and the biogeochemical factors that shape them at different soil depths, we analyzed microbial activities and bacterial and fungal community composition in soils up to a 120 cm depth at a fallow field located in central Korea. To examine the vertical difference of microbial activities and community composition, β-1,4-glucosidase, cellobiohydrolase, β-1,4-xylosidase, β-1,4-N-acetylglucosaminidase, and acid phosphatase activities were analyzed and barcoded pyrosequencing of 16S rRNA genes (bacteria) and internal transcribed spacer region (fungi) was conducted. Results: The activity of all the soil enzymes analyzed, along with soil C concentration, declined with soil depth. For example, acid phosphatase activity was 125.9 (± 5.7 (± 1 SE)), 30.9 (± 0.9), 15.7 (± 0.6), 6.7 (± 0.9), and 3.3 (± 0.3) nmol g-1 h-1 at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively. Among the bacterial groups, the abundance of Proteobacteria (38.5, 23.2, 23.3, 26.1, and 17.5% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) and Firmicutes (12.8, 11.3, 8.6, 4.3, and 0.4% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) decreased with soil depth. On the other hand, the abundance of Ascomycota (51.2, 48.6, 65.7, 46.1, and 45.7% at 15, 30, 60, 90, and 120 cm depths, respectively), a dominant fungal group at this site, showed no clear trend along the soil profile. Conclusions: Our results show that soil C availability can determine soil enzyme activity at different soil depths and that bacterial communities have a clear trend along the soil depth at this study site. These metagenomics studies, along with other studies on microbial functions, are expected to enhance our understanding on the complexity of soil microbial communities and their relationship with biogeochemical factors. [ABSTRACT FROM AUTHOR]

Effective nutrient management has the potential to be instrumental in reducing agricultural nonpoint source pollution. Relatively few agricultural producers, however, have voluntarily adopted nutrient management conservation practices, and many users do not follow each recommendation or implement practices on all of their applicable land. Most existing research has used a binary measure of adoption, meaning the ability to accurately predict and understand adoption levels of conservation practices is limited. A statewide survey of 1,320 agricultural landowners and producers in Indiana was conducted in early 2014 to collect information about awareness and usage of nutrient management practices. We use this data to explore the determinants of farmers' usage of four nutrient best management practices and test whether a more precise measurement of practice adoption results in better model fit. We find that while there is relatively high uptake of soil testing (85%), farmers in Indiana are less likely to use variable rate application, application timing, and nutrient management plans, and the degree to which farmers adopt practices varies. There were few consistent predictors of practice uptake, yet attending workshops for information, access to equipment, larger farm size, trust in crop consultants, and usage of conservation crop rotations were positive predictors of at least two of the four practices. Usage of an ordinal rather than a binary measure of adoption did not improve model predictability as hypothesized, suggesting that future research should continue to try novel measures. [ABSTRACT FROM AUTHOR]

Large-scale production of aromatic plants is subject to phytotechnical challenges, such as management, irrigation, nutrition, and soil fertility, as well as exogenous issues that may affect the chemical composition of secondary metabolites. The aim of this study was to evaluate the effect of organo-mineral fertilizer on the biomass and essential oil of lavender ( Lavandula dentata L.). A randomized block experimental design was used in a split-plot arrangement, consisting of five rates of organo-mineral fertilizer, and an additional treatment with only mineral fertilizer. The organo-mineral fertilizer was used at the same recommended rate as the mineral fertilizer. The organo-mineral fertilizer was formulated with 10% total nitrogen, 10% P 2 O 5 , 10% total potassium, and 8% organic carbon, and was applied at the following rates: 100%, 80%, 60%, 40%, and 20%. Flowers, leaves, and stems were harvested three times. Plant biomass, and the concentration, yield, and chemical composition of the essential oils were evaluated. Results showed that the highest flower yield was obtained at 145 days after planting through use of the 100% rate of the organo-mineral fertilizer. The 60% rate of the organo-mineral fertilizer produced more than 320 g plant −1 of fresh biomass. The major compounds were 1,8-cineole, camphor, and fenchone, and these compounds together represented more than 80% of the chemical composition. The organo-mineral fertilizer can ensure greater yield through slow release of nutrients around the root system, especially at the flowering stage. We conclude that associating organo-mineral fertilization with the appropriate harvest season has a noticeable impact on the chemical composition of lavender essential oil. [ABSTRACT FROM AUTHOR]

Questions: How do community-weighted means of traits (CWM) and functional dispersion (FDis), a measure of trait variability, change in response to gradients of temperature, precipitation, soil nutrients and disturbance? Is the decrease in trait similarity between plots continuous or discontinuous? Is species turnover between plots linked to trait turnover? Location: Mount Kilimanjaro, Tanzania, Africa. Methods: Sixty plots were established in 12 major vegetation types on Mount Kilimanjaro, covering large gradients of temperature, precipitation, soil nutrients and anthropogenic disturbance representing the dominant ecosystems in East Africa. Environmental data, plant abundances and plant traits were recorded for each plot. Trait CWM and FDis were related to environmental factors with partial least squares regressions. Trait similarity between pairs of plots was assessed with a null model approach. Results: Both CWM and FDis of most traits responded strongly to environmental factors, particularly to precipitation and disturbance. FDis of traits associated with growth and reproduction mostly increased with temperature and precipitation, and decreased with disturbance. Pair-wise plot comparisons revealed an inverse relationship of trait similarity with differences in temperature, precipitation and anthropogenic disturbance. However, changes in similarity were often discontinuous rather than continuous. Several vegetation types differed strongly in species composition but not in traits. Conclusions: Trait dispersion indicating functional niches increased with productivity and temperature. Conversely, low-productivity conditions were characterized by trait convergence. Discontinuous changes in trait similarity between plots suggested tipping points at which trait expressions change strongly to adjust to environmental conditions. Large sections of the temperature gradient were characterized by species turnover with only minor changes in traits, indicating that the functional composition may be resilient to gradual environmental changes until a tipping point is reached. [ABSTRACT FROM AUTHOR]

Recovery of vegetation and soil nutrients in abandoned shifting cultivation areas can provide important information, important for forest rehabilitation. For better understanding of forest recovery after the cessation of shifting cultivation, soil nutrients and vegetation structure of fallow areas were monitored at 1, 5 and 10 years after abandonment in a primary forest plot. The results showed that the number of species, the Shannon indices of diversity and evenness of large trees (diameter at breast height > 20 cm) increased with time after abandonment. Late-successional species in primary tropical rainforests, e.g. Shorea sp., was found 1, 5 and 10 years after abandonment. Soil organic carbon and total nitrogen levels were low in all plots and at all soil depths except in surface soil (0-2 cm), and did not significantly differ between among plots. Available phosphorous content was significantly different between the plot that had been fallow for one year and the rest of the plots, for both combined and each soil depth. It was concluded that changes in vegetation composition did not affect the status of soil nutrients in the young fallow plots, which can support the growth of late-succession species. [ABSTRACT FROM AUTHOR]

Maintenance of soil physical health at its optimum level is essential for sustainable crop production and rational use of natural resources without jeopardizing their quality. The ongoing conventional tillage practices for crop production using intensive ploughing and removal of crop residue from the field have resulted in an increase in surface crusting, soil compaction, soil erosion, decrease in water infiltration and ultimately aggravation of the overall soil physical health deterioration. In recent years, many agricultural scientists across the world have recommended conservation agriculture as a solution to overcome the adverse effects of conventional tillage practices on soil physical health. Conservation agriculture is mainly an integration of three crop management practices, viz. minimum or no-tillage, permanent retention of crop residue and crop rotation. The present data indicates that conservation agriculture can improve soil physical properties and associated processes especially, soil water infiltration and storage, soil aeration, soil structure and soil porosity. It reduces soil erosion, soil compaction and crusting, and optimizes the soil temperatures for successful crop production. This article reviews the role of conservation agriculture in improving soil physical health and its associated processes. [ABSTRACT FROM AUTHOR]

Questions Ellenberg nutrient values based on indicator plant species composition of vegetation plots (mN) are widely used to measure temporal and spatial patterns of nutrient deficiency and eutrophication. The widespread use is in contrast to the lack of direct calibration against soil chemical proxies of nutrient availability. Lack of calibration and range contraction due to averaging of a bounded ordinal scale hinder the interpretation of mN across studies. Based on a large set of concomitant vegetation-soil data we asked: (1) which is the best single soil predictor of mN, (2) which combination of soil variables best explains mN; and (3) can a meaningful relative scale of mN be provided for comparative purposes? Location Forests in Germany, sampled in a systematic 8 km × 8 km grid. Methods The German National Forest Soil Inventory ( NFSI) provides a large, representative sample of joint soil and vegetation plots, which were additionally intersected with modelled background N deposition. Values of mN of vegetation plots were related to measured 36 soil and three deposition variables by correlation and multiple regression. The distribution of mN was partitioned based on quantiles. Results In NFSI mN was most closely related to the C/N ratio of the topsoil ( r² = 0.31). Multiple analysis regression showed that soil acidity, soil P and K, humus quality and deposition were complementary predictors (multiple r² = 0.47) of mN. Conclusions Values of mN are moderately, but consistently, related to measurable chemical properties of forest soils. The 10, 30, 70 and 90% quantiles of the frequency distribution of mN in the NFSI data are proposed to define a relative scale of macronutrient availability in forest soils, distinguishing very oligotrophic (mN < 3.38), oligotrophic (3.38-4.8), mesotrophic (4.80-5.75), eutrophic (5.75-6.21) and highly eutrophic (>6.21) sites, which broadly correspond to conventional classes of C/N ratio used in forest site mapping. This proposed five-class trophic scale can be used to compare mN and its trends across studies in forest vegetation of Central Europe. [ABSTRACT FROM AUTHOR]

Virgilia divaricata is an indigenous forest margin legume growing in nutrient richer soils, but it is also known to invade the N and P poorer soils of the mature fynbos, a nutrient-poor ecosystem in the Cape Floristic Region of South Africa. Although this implies that the legume has a wide functional tolerance for variable soil N and P levels, it is not known how the plant utilizes inorganic N under variable P supply. The aim of this experiment was therefore to identify the nodulating bacterial species and their biological N 2 fixing (BNF) efficiencies in V. divaricata during P deficiency. Furthermore, the aim was to integrate plants C and N metabolism to the N product exported via xylem to the shoots. Plants were grown at high and low P levels, both the high and low P plants were then supplied with either 500 μM NH 4 NO 3 as soil nitrogen (N) source or exclusively relied on BNF. Although the bacterial composition of nodules remained seemingly unchanged by P and N supply, the nodule function was greatly altered. In this regard, plants reliant on only N 2 at both P levels had higher and more efficient BNF, which resulted in greater plant N. This may have resulted from two physiological strategies at high and low P, when plants relied only on N 2 fixation. The declines in both sugars and organic acids may imply a reduced energy supply to the bacteroid during P stress. Furthermore altered bacteroid function may be inferred from BNF, and the N compounds synthesized and exported. At high P, plants exported more amino acids relative to inorganic N and ureides in their xylem sap, whereas at low P the plants exported more ureides relative to amino acids and NH 4 . The bacterial tolerance for changes in P and N via nodule metabolites and xylem export might be a major factor that underpins the growth of V. divaricata under these variable soil conditions. [ABSTRACT FROM AUTHOR]

Ant-plant interactions have mainly been considered as a protection mutualism where ants increase plant performance through protection from herbivory. However, host plants may also benefit from nutrients deposited by ants. Nitrogen limits the plant growth in most terrestrial ecosystems and the nutrient exchange between ants and plants may be an important mechanism operating in ant-plant interactions. In this study, we quantified the exchange of macronutrients (carbon and nitrogen) between ants and plants, using the Asian weaver ant Oecophylla smaragdina as a model species in a mango agroecosystem. A method was developed with which the amount of nitrogen retrieved to their host trees could be predicted by the trail density of O. smaragdina. Ant nutrient consumption was calculated based on data on O. smaragdina abundance and per capita consumption rates obtained in laboratory colonies. On a yearly basis, the influx of nitrogen to the host tree, originating from captured prey, averaged 14.4 (range 8.0-46.4) kg N ha y. The loss of carbon from the host tree due to ant consumption of exudates from nectaries and tended homopterans averaged 278.1 (range 149.3-939.9) kg C ha y. O. smaragdina may provide their host plant with a significant source of nitrogen albeit a substantial amount of carbon is consumed from the host plant. This study reveals that the flow of nutrients between ants and plants may play a critical and underestimated role in ant-plant mutualisms. [ABSTRACT FROM AUTHOR]

Priming of soil organic matter decomposition by fresh carbon inputs is a key ecological process determining soil carbon (C) and nutrient cycling in terrestrial ecosystems. Although this priming effect (PE) has been studied under various environmental conditions, the conclusions are inconsistent across space and time and the underlying mechanisms unclear. We used a meta-analysis with extensive datasets of CO 2 effluxes from soils with 13 C or 14 C labelled fresh C inputs and without fresh C inputs under various soil conditions to synthesize and assess the temporal dynamics of the PE. The results indicated that the PE declined in 20 days on average from 67 − 21 + 26 % (95% confidence interval) immediately following the fresh C inputs to less than 7.6 − 1.8 + 2.0 % and remained relatively stable thereafter. We also assessed the variability of the temporal dynamics of the PE in the collected datasets and the underlying drivers. The results showed that the magnitude of PE at a specific time (i.e., the instantaneous PE after the fresh C inputs) was significantly and positively correlated with the instantaneous quantity of remaining fresh C. Under the same quantity of remaining fresh C, the PE varied significantly across ecosystems (in the order of grasslands < farmlands < forests < other ecosystems such as lake beds and volcanic soils), but, contrary to our expectation, the PE was independent of the quality of the added fresh C. We found that the PE experienced a faster decrease in soils with higher clay and moisture contents. These results describe the temporal dynamics of PE and the underlying drivers, underpinning the robust predictions of PE dynamics and their impact on soil C and nutrient balances. [ABSTRACT FROM AUTHOR]

The extent to which the wetted soil area of a urine patch influences surrounding pasture is relatively unknown. The study objective was to use15N tracer to quantify pasture N uptake in the ‘wetted’ and periphery areas of a spring deposited bovine urine patch over 311 days. Ruminant15N enriched urine was applied to soil creating a circular wetted area, ‘zone A’ (800 kg N ha−1), with and without urea fertiliser (35 kg N ha−1). Pasture yields,15N recovery and soil inorganic-N dynamics were monitored from zone A and two peripheral zones, B and C. Fertiliser had no effect on cumulative urinary15N recovery in pasture (50%–52%). Average cumulative pasture15N recovery in zones A, B and C were 30.6%, 17.3% and 4.2%, respectively. Soil inorganic-15N recovery occurred in zones A and B, declining with distance from the wetted area. The results suggest an effective urine patch area of 0.95 m2or 3.4 times the wetted area. [ABSTRACT FROM PUBLISHER]

Composts and soil conditioners may be useful soil amendments to provide organic matter as well as nutrients such as N and P, but net N mineralized and P released can vary greatly among materials. Consequently, it is important to identify the material characteristics that control these processes. Furthermore, the magnitude of these processes may be affected by particle size. We conducted two laboratory studies at 30°C to: (i) identify variables that can be used to estimate N mineralized and Mehlich-1 P released from 14 composts and soil conditioners; and (ii) evaluate net N mineralized from three size fractions (<1.0 mm, 1.0-2.0, and 2.0-4.0 mm) of five different composts. Organic N content and C/N ratio explained 83% of the variability in the amount of net N mineralized or immobilized per unit of material from the 14 composts or conditioners in 214 d. Similarly, organic N content and total P content explained 99% of the variability in the amount of Mehlich-1 P released per unit of material. In the study with size fractions, we found that larger size fractions (1-4 mm) mineralized more N (4% of applied N) than the 0- to 1-mm size fraction (0.5%). These results indicate that sieving composts to obtain specific size fractions may affect the rate of N mineralization. [ABSTRACT FROM AUTHOR]

The study was conducted during 2010 at Pir Mehr Ali Shah, Arid Agriculture University Rawalpindi, Pakistan, to screen soil additives with improved water retention. Different soil additives i.e. Qemisoyl, gypsum, compost and farm yard manure (FYM) were evaluated to quantify plant available water under controlled conditions. The samples of clay loam soil were subjected to various pressure levels (33 to 1500 kpa) to develop soil moisture characteristic curves. The results revealed that highest soil moisture content at field capacity (0.284 m3 m-3), permanent wilting point (0.146 m3 m-3) and plant available water content (0.138 m3 m-3) was recorded with the application of Qemisoyl @ 15 kg ha-1 as compared to control (0.251, 0.128 and 0.123 m3 m-3, respectively). Generally, the combined use of various soil additives was equivalent to their sole applications. The results indicated that soil moisture retention can be enhanced with the application of soil additives especially Qemisoyl @ 15 kg ha-1 that gave about 12% higher moisture retention than control to achieve higher levels of crop production in drought-hit areas to ensure food security. Further comprehensive field studies based on results of present laboratory study may help develop useful water harvesting/capturing interventions at the farm scale. [ABSTRACT FROM AUTHOR]

Gravel is common in soil profiles of alpine grassland on the Qinghai-Tibetan plateau (QTP). However, little is known about the effect of gravel on soil and vegetation properties. In this study, we investigated the gravel content in the topsoil (0–40 cm) at three sites with different surface gravel mulch and analyzed the influence of gravel on soil organic carbon (SOC), soil total nitrogen (TN), fractional vegetation cover (FVC), and aboveground biomass (AGB). Results showed that (1) gravel content was the highest in sites with high surface gravel mulch, and the lowest in sites with light surface gravel mulch; (2) gravel was significantly negatively correlated with SOC, TN, FVC and AGB, and (3) gravel of 2–20 mm in size was the most important factor determining soil and vegetation properties. Our results suggested that the presence of gravel in the soil profile is not beneficial to soil nutrition sequestration and vegetation growth of alpine grassland on the QTP and should be considered in ecosystem modeling studies. [ABSTRACT FROM AUTHOR]

Small-scale heterogeneity strongly affects plant fitness and many ecological processes, and it can significantly influence the growth of individual plants, populations and communities. Generally, clonal species achieve significantly more growth when essential resources are patchily distributed than when resources are uniformly distributed. In this study, we aim to determine the effect of spatial heterogeneity in soil resources on intraspecific competition in the clonal plant Glechoma hederacea. We report the outcomes of a greenhouse experiment where high and low densities of plants were exposed to patchy and uniform distribution of nutrients. Our results showed that patchy distribution of resources exacerbated intra-specific competition between clonal systems. We found a reduction of total mass of clonal systems growing at high-density, especially under patchy conditions. Patchy distribution of resources conduct to high concentration of resources located in small areas, and as consequence increase the competition interaction between plants. This study demonstrates that full understanding of plant-plant competitive interactions requires consideration of spatial heterogeneity in nutrient supply. [ABSTRACT FROM AUTHOR]

Aims The volume of soil beyond a plant’s roots from which that plant is able to acquire a particular nutrient depends upon the mobility of that nutrient in the soil. For this reason it has been hypothesized that the strength of competitive interactions between plants vary with soil nutrient mobility. We aimed to provide an experimental test of this hypothesis. Methods We devised two experimental systems to investigate specifically the effect of nutrient transport rates upon intraspecific competition. In the first, the exchange of rhizosphere water and dissolved nutrients between two connected pots, each containing one plant, was manipulated by alternately raising and lowering the pots. In the second experiment, the roots systems of two competing plants were separated by partitions of differing porosity, thereby varying the plants’ access to water and nutrients in the other plant′s rhizosphere. In this second experiment, we also applied varying amounts of nutrients to test whether higher nutrient input would reduce competition when competition for light is avoided, and applied different water levels to affect nutrient concentrations without changing nutrient supply. Important findings In both experiments, lower mobility reduced competitive effects on plant biomass and on relative growth rate (RGR), as hypothesized. In the second experiment, however, competition was more intense under high nutrient input, suggesting that low nutrient supply rates reduced the strength of the superior competitor. Competitive effects on RGR were only evident under the low water level, suggesting that under lower nutrient concentrations, competitive effects might be less pronounced. Taken together, our results provide the first direct experimental evidence that a reduction in nutrient mobility can reduce the intensity of competition between plants. [ABSTRACT FROM AUTHOR]

The article presents research on the correlation between soil respiration and belowground carbon allocation, with a focus on carbon cycling across global forest ecosystems. Topics include the allometric constraints on carbon allocation, the effect of climate change and global warming on soil respiration, heterotrophic respiration, nitrogen deposition, root respiration, and soil carbon dioxide (CO2) efflux.

The influence of tree species on soils has received much attention, but we know little about either the pattern and underlying mechanisms of net nutrient and carbon inputs under canopy for various tree species or the effects of net nutrient input on soil nutrient contents. To address these issues, we selected three tree species with distinct leaf sizes and arranged litter traps around the target individuals to test what affected net nutrient and carbon inputs under canopy of target individuals, and how net nutrient inputs influenced soil nutrient contents. The results showed that net litter manganese (Mn) and lignin inputs were significantly different among these tree species, as well as soil exchangeable potassium (K), available iron (Fe) and available Mn. The results also revealed that the species with the smallest sized leaves may stimulate more net Mn and lignin inputs than the species with the largest sized leaves. At the same time, net nutrient inputs correlated with soil available Fe, while the ratio of lignin to nitrogen of net litter correlated with total phosphorus contents. These results demonstrated that litter production may be the main factor deciding net nutrient and carbon inputs under different tree species' canopy, which significantly differentiated soil iron's availability. [ABSTRACT FROM AUTHOR]

The authors discuss aspects of phloem functions in whole-plant economy wherein it stand as an enigmatic central banker. They state that phloem transfer carbohydrates to sink photosynthetic tissue for growth, storage and respiration which drawn water from the xylem through osmosis. The authors note that the tree height may replace to response short trees to lower soil due to the difference in water potential from gravity.

Sustainable nutrient cycling in agroecosystems combining grazing and crops has global ramifications for protecting these ecosystems and for the livelihoods they support. We sought to understand environmental, management, and social drivers of nutrient management and sustainability in Andean grazing/crop systems. We assessed the impact of farmer wealth, fields’ proximity to villages, topography, and rangeland net primary productivity (NPP) on mass balances for nitrogen (N), phosphorus (P), and potassium (K) of 43 fields. Wealthier farmers applied greater total amounts (kg) of manure nutrients. However, higher manure application rates (kg ha −1) were associated with field proximity and NPP rather than wealth. Manure P inputs in far fields (> 500-m distant) were half those in near fields. Harvest exports increased with manure inputs ( P < 0.001) so that balances varied less than either of these flows. Erosion nutrient losses in steeper far fields matched crop exports, and yields declined with increasing field slope ( P < 0.001), suggesting that erosion reduces productivity. Balances for P were slightly positive in near and far fields (+2.2 kg P ha −1 y −1, combined mean) when calculated without erosion, but zero in near fields and negative in far fields with erosion included (−6.1 kg P ha −1 y −1 in far fields). Near/far differences in both inputs and erosion thus drove P limitation. Crop K exports dominated K balances, which were negative even without accounting for erosion. Modeled intensification scenarios showed that remediating far field deficits would require P addition and erosion reduction. Management nested within environmental constraints (NPP, erosion) rather than socioeconomic status drives soil nutrient sustainability in these agroecosystems. Time-lags between management and long-term degradation are a principal sustainability challenge to farming in these montane grazing/crop agroecosystems. [ABSTRACT FROM AUTHOR]