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As exotic plants invade into a new range, they can escape from specialist enemies. However, they may support generalist enemies, including both native and introduced fungal pathogens, which creates the potential for spillover and apparent competition from exotic to native plants in communities.To assess the potential for spillover of putatively pathogenic, root‐associated fungi (hereafter, 'pathogens') in communities invaded by exotic plants, we conducted a two‐phase plant–soil feedback experiment: a monoculture experiment with native and exotic plants grown alone and a multi‐species, community‐level experiment that ranged in the extent of exotic dominance. We used next‐generation sequencing to characterise sharing of pathogens between native and exotic plants in communities.Exotic plants outperformed natives in communities, despite harbouring higher relative abundance of generalist pathogens. The higher generalism of pathogens supported by exotic plants made them more prone to be shared with natives. The proportion of pathogens shared between exotic and native plants in communities correlated with reduced competitive ability of native compared with exotic plants.Synthesis: These data suggest that exotic plants host more generalist pathogens that are shared with native plants, which may confer an indirect benefit to exotic over native plants through apparent competition. [ABSTRACT FROM AUTHOR]

The efficiency of soil phosphorus (P) mobilization and uptake by plants depends on a complex combination of factors, including plant P acquisition strategies and soil P availability. The objective of this study was to assess and compare the capabilities of three legume species (blue lupin (Lupinus angustifolius L.), faba bean (Vicia faba L.), and chickpea (Cicer arietinum L.)), which may be used as green manures in temperate crop systems to acquire P from a soil with different levels of plant‐available P. Three cycles of each legume were grown in a glasshouse over a 6 month period in the same soil type with high (Olsen P: 47 mg kg−1) and low (Olsen P: 9 mg kg−1) levels of plant‐available P. Measurements included above—and below—ground plant biomass and P uptake, in addition to determination of acid and alkaline phosphomonoesterase activities, microbial P, and P fractions in soil at the end of the experiment. In both soils, plant biomass, P uptake, and microbial P were all higher under faba bean compared to blue lupin and chickpea (p <.05). In the low‐P soil, faba bean increased alkaline phosphomonoesterase activity (p <.05). Significant depletion of inorganic P in the soluble (46%–69%), labile (29%–42%), and moderately labile (15%–16%) pools and increase of organic P in the labile (13%–18%) and total (7%–13%) pools occurred under faba bean compared with blue lupin, while changes under chickpea were between those determined for faba bean and blue lupin (p <.05). The findings of this study indicated that inclusion of faba bean green manure may have the potential to improve overall P use efficiency by enhancing mobilization of labile soil inorganic P, although further research is required to investigate mobilization of more stable forms of soil legacy P and quantify the potential of faba bean as a green manure crop under field conditions. [ABSTRACT FROM AUTHOR]

A defining feature of the Anthropocene is the distortion of the biosphere phosphorus (P) cycle. A relatively sudden acceleration of input fluxes without a concomitant increase in output fluxes has led to net accumulation of P in the terrestrial‐aquatic continuum. Over the past century, P has been mined from geological deposits to produce crop fertilizers. When P inputs are not fully removed with harvest of crop biomass, the remaining P accumulates in soils. This residual P is a uniquely anthropogenic pool of P, and its management is critical for agronomic and environmental sustainability. Managing residual P first requires its quantification—but measuring residual P is challenging. In this review, we synthesize approaches to quantifying residual P, with emphasis on advantages, disadvantages, and complementarity. Common approaches to estimate residual P are mass balances, long‐term experiments, soil test P trends and chronosequences, with varying suitability or even limitations to distinct spatiotemporal scales. We demonstrate that individual quantification approaches are (i) constrained, (ii) often complementary, and (iii) may be feasible at only certain time–space scales. While some of these challenges are inherent to the quantification approach, in many cases there are surmountable challenges that can be addressed by unifying existing P pool and flux datasets, standardizing and synchronizing data collection on pools and fluxes, and quantifying uncertainty. Though defined as a magnitude, the distribution and speciation of residual P is relatively less understood but shapes its utilization and environmental impacts. The form of residual P will vary by agroecosystem context due to edaphoclimatic‐specific transformation of the accumulated P, which has implications for management (e.g., crop usage) and future policies (e.g., lag times in P loading from non‐point sources). Quantifying the uncertainty in measuring residual P holds value beyond scientific understanding, as it supports prioritization of monitoring and management resources and inform policy. [ABSTRACT FROM AUTHOR]

Microbial community structure and function were assessed in the organic and upper mineral soil across a ~4000‐year dune‐based chronosequence at Big Bay, New Zealand, where total P declined and the proportional contribution of organic soil in the profile increased with time. We hypothesized that the organic and mineral soils would show divergent community evolution over time with a greater dependency on the functionality of phosphatase genes in the organic soil layer as it developed. The structure of bacterial, fungal, and phosphatase‐harbouring communities was examined in both horizons across 3 dunes using amplicon sequencing, network analysis, and qPCR. The soils showed a decline in pH and total phosphorus (P) over time with an increase in phosphatase activity. The organic horizon had a wider diversity of Class A (phoN/phoC) and phoD‐harbouring communities and a more complex microbiome, with hub taxa that correlated with P. Bacterial diversity declined in both horizons over time, with enrichment of Planctomycetes and Acidobacteria. More complex fungal communities were evident in the youngest dune, transitioning to a dominance of Ascomycota in both soil horizons. Higher phosphatase activity in older dunes was driven by less diverse P‐mineralizing communities, especially in the organic horizon. [ABSTRACT FROM AUTHOR]

Soil microbes and phosphatase enzymes play a critical role in organic soil phosphorus (P) cycling. However, how long‐term P inputs influence microbial P transformations and phosphatase enzyme activity under grazed pastures remains unclear. We collected top‐soil (0–75 mm) from a grazed pasture receiving contrasting P inputs (control, 188 kg ha−1 year−1 of single super phosphate [SSP], and 376 kg ha−1 year−1 of SSP) for more than 65 years. Olsen P, microbial biomass P, and acid and alkaline phosphatase enzyme activities were measured regularly over a 2‐year period. Pasture dry matter and soil chemical properties were also investigated. Results showed that long‐term P inputs significantly increased pasture dry matter, total N, and the concentrations of NO3––N but significantly decreased soil pH and the concentrations of NH4+–N. Total C was not affected by P fertilization. Although Olsen P significantly increased with increasing long‐term P inputs, microbial biomass P was similar under P fertilized treatments. Long‐term P inputs decreased acid phosphatase activity but increased alkaline phosphatase activity. Microbial biomass P was similar across seasons in the control but decreased in spring and autumn while increased in summer and winter under P fertilized treatments. Acid and alkaline phosphatase activities were significantly affected by season and followed similar seasonal trends being maximum in summer and minimum in winter regardless of P treatment. Correlation and principal component analysis revealed that acid and alkaline phosphatase activities were significantly positively correlated with soil temperature and significantly negatively correlated with soil moisture. In contrast, Olsen P and microbial biomass P were weakly correlated with environmental conditions. The findings of this study highlight the intertwined relationship between organic P cycling and the availability of C and N in soil systems and the need to integrate both soil moisture and temperature in models predicting organic P mineralization, especially in the context of global climate change. [ABSTRACT FROM AUTHOR]

New Zealand's ancient kauri (Agathis australis) forests are under threat from the spread of dieback disease, caused by the soil‐borne pathogen Phytophthora agathidicida. Characterizing the response of the soil microbiota to the infection of kauri with P. agathidicida is essential to identify how they may form a protective response to pathogen invasion and disease expression. This study infected 18‐month‐old kauri seedlings with a standardized inoculum load of P. agathidicida for 6 weeks under controlled environmental conditions. Following this, changes in the diversity, composition and biomass of soil microbial communities associated with kauri seedlings were characterized using high‐throughput 16S rRNA and ITS gene region sequencing and phospholipid fatty acid analysis. Significant differences were found in the composition of soil bacterial communities associated with inoculated and non‐inoculated kauri seedlings. Furthermore, soils of inoculated seedlings had a significantly higher relative abundance of bacteria previously reported to be associated with plant disease suppression, which included several members of the Firmicutes. Significant reductions were found in the fungal: bacterial biomass of soils from inoculated seedlings. This finding contrasts to previous field‐based research that observed an increased diversity of soil fungal communities associated with diseased kauri in old growth kauri forests. Further research that aims to isolate members of the kauri soil microbiota and study their interactions with P. agathidicida is required for us to begin selecting potential biocontrol agents against kauri dieback. [ABSTRACT FROM AUTHOR]

Erosion leading to sedimentation in surface water may disrupt aquatic habitats and deliver sediment‐bound nutrients that contribute to eutrophication. Land use changes causing loss of native vegetation have accelerated already naturally high erosion rates in New Zealand and increased sedimentation in streams and lakes. Sediment‐bound phosphorus (P) makes up 71–79% of the 17–19 t P y−1 delivered from anthropogenic sources to Lake Rotorua in New Zealand. Detainment bunds (DBs) were first implemented in the Lake Rotorua catchment in 2010 as a strategy to address P losses from pastoral agriculture. The bunds are 1.5–2 m high earthen stormwater retention structures constructed across the flow path of targeted low‐order ephemeral streams with the purpose of temporarily ponding runoff on productive pastures. The current DB design protocol recommends a minimum pond volume of 120 m3 ha−1 of contributing catchment with a maximum pond storage capacity of 10 000 m3. No previous study has investigated the ability of DBs to decrease annual suspended sediment (SS) loads leaving pastoral catchments. Annual SS yields delivered to two DBs with 20 ha and 55 ha catchments were 109 and 28 kg SS ha−1, respectively, during this 12‐month study. The DBs retained 1280 kg (59%) and 789 kg (51%) of annual SS loads delivered from the catchments as a result of the bunds' ability to impede stormflow and facilitate soil infiltration and sediment deposition. The results of this study highlight the ability of DBs to decrease SS loads transported from pastures in surface runoff, even during large storm events, and suggests DBs are able to reduce P loading in Lake Rotorua. [ABSTRACT FROM AUTHOR]

Bloom et al. proposed that rising atmospheric CO2 concentrations 'inhibit malate production in chloroplasts and thus impede assimilation of nitrate into protein of C3 plants, a phenomenon that will strongly influence primary productivity and food security under the environmental conditions anticipated during the next few decades'. Previously we argued that the weight of evidence in the literature indicated that elevated atmospheric [CO2] does not inhibit NO3− assimilation in C3 plants. New data for common bean (Phaseolus vulgaris) and wheat (Triticum aestivum) were presented that supported this view and indicated that the effects of elevated atmospheric [CO2] on nitrogen (N) assimilation and growth of C3 vascular plants were similar regardless of the form of N assimilated. Bloom et al. strongly criticised the arguments presented in Andrews et al. Here we respond to these criticisms and again conclude that the available data indicate that elevated atmospheric [CO2] does not inhibit NO3− assimilation of C3 plants. Measurement of the partitioning of NO3− assimilation between root and shoot of C3 species under different NO3− supply, at ambient and elevated CO2 would determine if their NO3− assimilation is inhibited in shoots but enhanced in roots at elevated atmospheric CO2. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) can accumulate in soil from the application of phosphorus fertilizer. However, there is little information on what happens to soil Cd concentrations when Cd inputs stop. This study used soil and pasture samples collected from a long‐term field trial to measure changes in Cd concentrations in soil for 22 yr after Cd inputs from fertilizer had stopped and assessed whether the application of nitrogen (N) (50 kg ha−1 yr−1) could increase plant uptake of Cd and reduce soil Cd concentrations. It was found that there was no significant change in total or labile soil Cd (1 M CaCl2 extractable) concentrations after Cd inputs stopped. The application of N did not significantly (P <.05) increase dry matter yield or increase Cd solubility. As a result, N did not enhance plant uptake of Cd. A mass balance that included Cd loss via plant uptake and Cd leaching confirmed they were insufficient to result in a detectable decrease in soil Cd concentration over the 22‐yr interval of the trial. It appears that even an acid soil with low amounts of carbon (2.67%), iron/aluminum oxides, and clay can still strongly retain Cd, preventing Cd depletion from the soil, despite stopping Cd inputs and trying to enhance plant uptake of Cd from the application of N fertilizer. [ABSTRACT FROM AUTHOR]

The added value of biochar when applied along with fertilizers, beyond that of the fertilizers themselves, has not been summarized. Focusing on direct comparisons between biochar additions (≤20 t ha−1) – separately considering the addition or not of inorganic fertilizers (IF) and/or organic amendments (OA) along with biochar – and two different controls (with and without the addition of IF and/or OA), we carried out a meta‐analysis to explain short‐term (1‐year) field responses in crop yield across different climates, soils, biochars and management practices worldwide. Compared with the non‐fertilized control, a 26% (CI: 15%–40%) increase in yield was observed with the use of IF only, whereas that of biochar along with IF caused a 48% (CI: 30%–70%) increase. Compared with the use of IF only, the addition of biochar along with IF caused a 15% (CI: 11%–19%) increase in yield, indicating that biochar was as effective as fertilizers in increasing crop yields when added in combination. The use of biochar alone did not increase crop yield regardless of the control considered. Whereas in the short term, liming may have partly contributed to the beneficial effect of biochar (>90% was plant‐derived) when added along with IF, a separate meta‐analysis – using those studies that reported crop yields for different years after a single biochar application – showed a 31% (CI: 17%–49%) increase in crop yield over time (≥ 3 years), which denotes the influence of biochar properties other than liming (i.e. an increase in CEC). Our results also suggest that biochar application rates > 10 t ha−1 do not contribute to greater crop yield (at least in the short term). Data limitations precluded identification of the influence of feedstock, production conditions or climatic conditions without bias. As the response of crop yield to biochar addition was less a result of climatic zones or soil type than fertilizer use (chiefly N additions), the choice of nutrient addition along with biochar should be priorities for future research and development regardless of the region. [ABSTRACT FROM AUTHOR]

The use of phosphorus (P) fertilizers in arable crop and pastoral systems is expected to change as modern agriculture is challenged to produce more food with fewer inputs. Agricultural systems models offer a dual purpose to support and integrate recent scientific advances and to identify strategies for farmers to improve nutrient efficiency. However, compared with nitrogen and carbon, advances in P modeling have been less successful. We assessed the potential opportunity of P modeling to increase P efficiency for modern agriculture and identified the current challenges associated with modeling P dynamics at the field scale. Three major constraints were (i) a paucity of detailed field datasets to model strategies aimed at increasing P use efficiency, (ii) a limited ability to predict P cycling and availability under the local effects of climate change, and (iii) a restricted ability to match measured soil P fractions to conceptual and modelable pools in soils with different mineral properties. To improve P modeling success, modelers will need to walk a tightrope to balance the roles of assisting detailed empirical research and providing practical land management solutions. We conclude that a framework for interdisciplinary collaboration is needed to acquire suitable datasets, continually assess the need for model adjustment, and provide flexibility for progression of scientific theory. Such an approach is likely to advance P management for increased P use efficiency. Core Ideas: Models can complement research and identify strategies to increase P efficiency.A variety of quality long‐term field trials is needed to advance model capabilities.Well‐calibrated soil models are needed to assess climate change impacts on P cycling.A framework is needed to streamline multidisciplinary research to improve P management. [ABSTRACT FROM AUTHOR]

Phosphorus derived from agricultural systems has been found to cause eutrophication of surface waters. To combat this, the specific location of soil profile P release is necessary for development of effective mitigation strategies. This paper describes a P leaching study of two Swedish arable soils, an organic (Typic Haplosaprist) and a mineral soil (Typic Hapludalf), both with high P content. Undisturbed soil columns isolated 0- to 20-, 20- to 40-, 40- to 60-, and 60- to 80-cm depth intervals. These were placed in a rainfall simulator and subjected to four 50-mm rainfall events to identify the origin of P leachate as a function of soil depth interval and physicochemical properties. Phosphorus losses were greatest from the two uppermost layers of both soils after 200 mm of artificial rainfall was applied at 5 mm h-1. Total P concentration in leachate from the 0- to 20-cm layer ranged from 2.1 to 8.8 mg L-1 for the mineral and 3.7 to 10.3 mg L-1 from the organic soil, with most (95-100%) in dissolved reactive P form. Degree of P saturation correlated well with total P leaching losses from the organic soil (R = 0.84) but not the mineral soil (R = 0.69), suggesting that the presence of Al and Fe (hydr) oxides has a stronger influence on P leaching in the organic soil. Results indicate that both soils have the potential to contribute concentrations of P above those known to cause eutrophication of surface waters. [ABSTRACT FROM AUTHOR]

Reduction of the potent greenhouse gas nitrous oxide (N2O) occurs in soil environments by the action of denitrifying bacteria possessing nitrous oxide reductase (N2 OR), a dimeric copper (Cu)-dependent enzyme producing environmentally benign dinitrogen (N2). We examined the effects of increasing Cu concentrations on the transcription and activity of nitrite reductase ( NIR), nitric oxide reductase ( NOR) and N2 OR in Pseudomonas stutzeri grown anaerobically in solution over a 10-day period. Gas samples were taken on a daily basis and after 6 days, bacterial RNA was recovered to determine the expression of nirS, norB and nosZ encoding NIR, NOR and N2 OR respectively. Results revealed that 0.05 mM Cu caused maximum conversion of N2O to N2 via bacterial reduction of N2O. As soluble Cu generally makes up less than 0.001% of total soil Cu, extrapolation of 0.05 mg l−l soluble Cu would require soils to have a total concentration of Cu in the range of, 150-200 μg g−1 to maximize the proportion of N2O reduced to N2. Given that many intensively farmed agricultural soils are deficient in Cu in terms of plant nutrition, providing a sufficient concentration of biologically accessible Cu could provide a potentially useful microbial-based strategy of reducing agricultural N2O emissions. [ABSTRACT FROM AUTHOR]

The bacterium Burkholderia sp. Ha185 readily solubilizes inorganic phosphate by releasing the low molecular weight organic anion, 2-ketogluconate. Using random transposon mutagenesis and in silico analysis, a mutation that caused almost complete abolition of phosphate solubilization was located within hemX, which is part of the hem operon. Burkholderia sp. Ha185 HemX is a multidomain protein, predicted to encode a bifunctional uroporphyrinogen-III synthetase/uroporphyrin-III C-methyltransferase, which has not previously been implicated in phosphate solubilization. Complementation of hemX restored the ability of the mutant to solubilize phosphate in both plate and liquid cultures. Based on a combination of organic-anion profiling, quantitative polymerase chain reaction and in silico analyses, hemX was confirmed to be solely responsible for hydroxyapatite solubilization in Burkholderia sp. Ha185. It is proposed that the biosynthesis of a yet to be determined redox cofactor by HemX is the main pathway for generating 2-ketogluconate via a haem-dependent gluconate 2-dehydrogenase in Burkholderia sp. Ha185. [ABSTRACT FROM AUTHOR]

The functional resistance and resilience of soils from across the South Island of New Zealand were assessed. Soils were collected from under varying land-uses (pasture, pine forest, native forest) at each of four different locations ( Hokitika, Craigieburn, Eyrewell, Orton Bradley Park). Soil function was measured using carbon utilization profiles ( Micro Resp technique), and responses to freeze-thaw disturbance assessed in a multivariate approach. Resistance was defined as the amount of change in functional profiles (multivariate distance) before, and then 10 h after, disturbance. Resilience was defined as the stability in ecosystem function over time (6 sample points spanning 17 days after initial freeze-thaw disturbance). The functional resistance of soils was not linked to land-use nor sampling location ( permanova P > 0.05) but was negatively correlated with soil Olsen- P levels (biological-environmental matching (BIO-ENV test); ρ = 0.604, P = 0.04). Secondary factors associated with soil organic matter status were associated with functional resistance in soil of low Olsen- P. This was explicitly tested by repeating the experiment in soils collected from a long-term P fertilizer management trial; functional resistance remained linked to the underlying P status of the soils ( P = 0.002). The functional stability of soil (post-disturbance) was associated with long-term rainfall (canonical analysis on principal coordinates - CAP analysis; P = 0.039); soils from high rainfall sites were more stable after disturbance. The results show that variables linked to functional resistance and resilience in soils are different. Furthermore, resilience was not correlated with resistance, or with measures of functional diversity (e.g. evenness of substrate mineralization). Alteration of the P status of soils is likely to impact on the capacity of soils to rapidly respond to disturbance, whereas drivers of climate, such as global warming, may impact soil functional resilience. [ABSTRACT FROM AUTHOR]

Many factors affect the magnitude of nutrient losses from dairy farm systems. Bayesian Networks (BNs) are an alternative to conventional modeling that can evaluate complex multifactor problems using forward and backward reasoning. A BN of annual total phosphorus (TP) exports was developed for a hypothetical dairy farm in the south Otago region of New Zealand and was used to investigate and integrate the effects of different management options under contrasting rainfall and drainage regimes. Published literature was consulted to quantify the relationships that underpin the BN, with preference given to data and relationships derived from the Otago region. In its default state, the BN estimated loads of 0.34 ± 0.42 kg TP ha-1 for overland flow and 0.30 ± 0.19 kg TP ha-1 for subsurface flow, which are in line with reported TP losses in overland flow (0-1.1 kg TP ha-1) and in drainage (0.15-2.2 kg TP ha-1). Site attributes that cannot be managed, like annual rainfall and the average slope of the farm, were found to affect the loads of TP lost from dairy farms. The greatest loads (13.4 kg TP ha-1) were predicted to occur with above-average annual rainfall (970 mm), where irrigation of farm dairy effluent was managed poorly, and where Olsen P concentrations were above pasture requirements (60 mg kg-1). Most of this loading was attributed to contributions from overland flow. This study demonstrates the value of using a BN to understand the complex interactions between site variables affecting P loss and their relative importance. [ABSTRACT FROM AUTHOR]

The physicochemical and biological gradients of soil and vegetative succession along the Franz Josef chronosequence in New Zealand were used to test whether bacterial communities show patterns of change associated with long-term ecosystem development. Pyrosequencing was conducted on soil-derived 16S rRNA genes at nine stages of ecosystem progression and retrogression, ranging in age from 60 to c. 120 000 years since glacial retreat. Bray- Curtis ordination indicated that the bacterial communities showed clear patterns of change that were closely aligned with ecosystem development, pedogenesis and vegetative succession ( Mantel test; r = 0.58; P < 0.001). Eighty per cent (80%) of the explained variability in bacterial community structure was observed during the first c. 1000 years of development, when bacterial richness ( Simpson's 1/ D) declined from 130 to 30. The relatively high turnover of soil bacterial communities corresponded with an integrative 'plant-microbial successional feedback' model that predicts primarily negative feedbacks between plants and soil bacterial communities during progression and early pedogenesis. Positive feedbacks, similar to those of the plant community, could explain the long periods of community stability during later retrogressive stages of ecosystem development. This hypothesized model provides a consistent description linking belowground communities to ecosystem development and succession. The research, using deep sequencing technology, provides the first evidence for soil bacterial community change associated with the process of long-term ecosystem development. How these bacterial community changes are linked to the processes of primary ecosystem succession is not known and needs further investigation. [ABSTRACT FROM AUTHOR]

The inventory of soil phosphorus (P) is subject to significant changes over time. The main primary form, bedrock-derived apatite P, becomes progressively lost through leaching, or transformed into more immobile and less plant-accessible, secondary organic and mineral forms. Here we studied the rejuvenating effect of dust deposition on soil P along an active dust flux gradient downwind of a braided river. Along the gradient, we measured soil P fractions to 50 cm depth of six Spodosols and one Inceptisol, supplemented by tree foliage P concentrations. While an increasing dust flux correlates with a twofold increase of foliar P and soil organic P along the gradient, apatite P declines from ~50 to 3 g m-2 and total P shows no response. Compared to dust-unaffected Spodosols, depth distribution of total P becomes increasingly uniform and organic P propagates deeper into the soil under dust flux. Further, the effect of topsoil P eluviation attenuates due to higher organic P content and the zone of high apatite P concentrations associated with un-weathered subsoil becomes progressively removed from the upper 50 cm. We interpret these patterns as being consistent with upbuilding pedogenesi and conclude that dust-derived mineral P is assimilated in the organic surface horizon and does not reach the mineral soil. Dust-derived mineral P is temporarily stored in the living biomass and returns to the soil with plant and microbial detritus as organic P, which is subsequently buried by further dust increments. We further conclude that (1) the efficiency of P fertilization of the ecosystem by dust accession is higher than through P advection in dust-unaffected Spodosols and (2) organic P may serve as an important source of labile P in a high-leaching environment. [ABSTRACT FROM AUTHOR]

The article offers information on a research conducted on the in situ effect of incorporating biochar into soil on nitrous oxide emissions from bovine urine patches and linked pasture uptake of nitrogen (N). It mentions that ruminant urine derived nitrous oxide fluxes has been used to investigate the effects of biochar rate following soil incorporation. It reports that nitrous oxide emissions from control plots reduces the emission factor from urine by 70 percent. It informs that soil concentrations decrease with increasing biochar rate during first urine deposition process.

The article focuses the association of biochar with the nitrogen (N) cycle in the soil. It explores several studies related to biochar's ammonia (NH3) adsorption capacity and to the exchange ability of soil cation including one on the effect of pyrolysis temperature on NH3 adsorption capacity of bamboo-manufactured biochar. It tackles the improvement of nitrification rates in forest systems due to phenol and terpene adsorption. It discusses several researches on biochar and N cycle perturbation including the possible application of biochar to animal waste composting as a bulking agent. It suggests to study the rate of cation exchange capacity (CEC) development and the role of biochar in N losses reduction.

Atmospheric concentrations of the greenhouse gas nitrous oxide (N2O) have continued to rise since the advent of the industrial era, largely because of the increase in agricultural land use. The urine deposited by grazing ruminant animals is a major global source of agricultural N2O. With the first commitment period for reducing greenhouse gas emissions under the Kyoto Protocol now underway, mitigation options for ruminant urine N2O emissions are urgently needed. Recent studies showed that increasing the urinary concentration of the minor urine constituent hippuric acid resulted in reduced emissions of N2O from a sandy soil treated with synthetic bovine urine, due to a reduction in denitrification. A similar effect was seen when benzoic acid, a product of hippuric acid hydrolysis, was used. This current laboratory experiment aimed to investigate these effects using real cow urine for the first time. Increased concentrations of hippuric acid or benzoic acid in the urine led to reduction of N2O emissions by 65% (from 17% to <6% N applied), with no difference between the two acid treatments. Ammonia volatilization did not increase significantly with increased hippuric acid or benzoic acid concentrations in the urine applied. Therefore, there was a net reduction in gaseous N loss from the soil with higher urinary concentrations of both hippuric acid and benzoic acid. The results show that elevating hippuric acid in the urine had a marked negative effect on both nitrification and denitrification rates and on subsequent N2O fluxes. This study indicates the potential for developing a novel mitigation strategy based on manipulation of urine composition through ruminant diet. [ABSTRACT FROM AUTHOR]

Phosphorus losses from soils have been reported to impair the water quality, resulting in deaths of fish and other marine animals, and can harm haman health. The objective of this study was to determine the seasonal distribution of P forms and losses in leachate collected from intact soil monoliths (70-cm depth, 50-cm diam.) of a Lismore stony silt loam soil (fine-loamy, mixed, superactive, frigid Aquic Camulic Hapludoll) during a 2-yr period. The experiment included different combinations of mineral P fertilizer at 45 or 90 kg P ha-1 yr-1 and/or farm dairy effluent (FDE) at 200 or 400 kg N ha-1 yr-1, which contained 41 to 95 kg P ha-1 yr-1. Amounts and forms of P in leachate collected during the irrigation (IR; November-April) and nonirrigation (NIR; May-October) seasons were compared. Results showed that P losses were higher in particulate forms (mainly particulate unreactive phosphorus, PUP) during the IR seasons. This may be because of regular inputs of high intensity flood IR (92 mm per application), which increased the dislocation of particles in the soil profile, thereby resulting in higher PUP losses. On the other hand, the amount of natural rainfall was much lower (usually <20 mm per event) during the NIR seasons that resulted in less dislocation of particles compared with the IR seasons; hence, lower P losses as PUP but higher losses as dissolved unreactive phosphorus (DUP). Variation in P losses during the different seasons suggest the need to develop mitigation strategies that should focus on reducing DUP losses during the NIR and PUP losses during the IR season. [ABSTRACT FROM AUTHOR]

Methanotrophic bacteria oxidize methane (CH4) in forest soils that cover ∼30% of Earth's land surface. The first measurements for a pristine Southern Hemisphere forest are reported here. Soil CH4 oxidation rate averaged 10.5±0.6 kg CH4 ha−1 yr−1, with the greatest rates in dry warm soil (up to 17 kg CH4 ha−1 yr−1). Methanotrophic activity was concentrated beneath the organic horizon at 50–100 mm depth. Water content was the principal regulator of ( r2=0.88) from the most common value of field capacity to less than half of this when the soil was driest. Multiple linear regression analysis showed that soil temperature was not very influential. However, inverse co-variability confounded the separation of soil water and temperature effects in situ. Fick's law explained the role of water content in regulating gas diffusion and substrate supply to the methanotrophs and the importance of pore size distribution and tortuosity. This analysis also showed that the chambers used in the study did not affect the oxidation rate measurements. The soil was always a net sink for atmospheric CH4 and no net CH4 (or nitrous oxide, N2O) emissions were measured over the 17-month long study. For New Zealand, national-scale extrapolation of our data suggested the potential to offset 13% of CH4 emissions from ca. 90 M ruminant animals. Our average was about 6.5 times higher than rates reported for most Northern Hemisphere forest soils. This very high was attributed to the lack of anthropogenic disturbance for at least 3000–5000 years and the low rate of atmospheric nitrogen deposition. Our truly baseline data could represent a valid preagricultural, preindustrial estimate of the soil sink for temperate latitudes. [ABSTRACT FROM AUTHOR]

Abstract We studied soil organic carbon (C) chemistry at the mountain birch forest-tundra ecotone in three regions of the Fennoscandian mountain range with comparable vegetation cover but contrasting degrees of continentality and latitude. The aim of the study was to identify functional compound classes and their relationships to decomposition and spatial variation across the ecotone and latitudinal gradient. Solid-state 13 C nuclear magnetic resonance (CPMAS 13 C NMR) was used to identify seven functional groups of soil organic C: alkyls , N-alkyls , O-alkyls , acetals , aromatics , phenolics and carboxyls . N-alkyls , O-alkyls and acetals are generally considered labile substrates for a large number of saprotrophic fungi and bacteria, whilst phenolics and aromatics are mainly decomposed by lignolytic organisms and contribute to the formation of soil organic matter together with aliphatic alkyls and carboxyls . All soils contained a similar proportional distribution of functional groups, although relatively high amounts of N-alkyls , O-alkyls and acetals were present in comparison to earlier published studies, suggesting that large amounts of soil C were potentially vulnerable to microbial degradation. Soil organic matter composition was different at the most southerly site (Dovrefjell, Norway), compared with the two more northerly sites (Abisko, Sweden, and Joatka, Norway), with higher concentrations of aromatics and phenolics , as well as pronounced differences in alkyl concentrations between forest and tundra soils. Clear differences between mountain birch forest and tundra heath soil was noted, with generally higher concentrations of labile carbon present in tundra soils. We conclude that, although mesic soils around the forest-tundra ecotone in Fennoscandia are a potential source of C to the atmosphere in a changing environment, the response is likely to vary between comparable ecosystems in relation to latitude and continentality as... [ABSTRACT FROM AUTHOR]

Soil P composition can be conveniently determined in alkaline extracts using solution [sup 31]P nuclear magnetic resonance (NMR) spectroscopy, but spectral assignments are based on fragmentary literature reports of model compounds in various extraction matrices. We report solution [sup 31]P NMR chemical shills of model P compounds, including inorganic phosphates, orthophosphate monoesters and diesters, phosphonates, and organic polyphosphates, determined in a standard, ed soil P extractant (0.25 M NaOH and 0.05 M EDTA). Signals from nucleic acids (DNA -0.37 ppm, RNA 0.54 ppm) and phospholipids (phosphatidyl choline 0.78 ppm, phosphatidyl serine 1.57 ppm, phosphatidyl ethanolamine 1.75 ppm) could be differentiated in the orthophosphate diester region, and were identified in a sample of cultured soil bacteria. Inorganic and organic polyphosphates could be differentiated by the presence of a signal at -9 ppm from the α phosphate of organic polyphosphates. Some orthophosphate diesters, notably RNA and phosphatidyl choline, degraded rapidly to orthophosphate monoesters in NaOHEDTA although DNA, other phospholipids, and orthophosphate monoesters were more stable. Changes in probe temperature had a marked influence on signal intensities and the relative magnitude of signals from orthophosphate monoesters and inorganic orthophosphate, and we suggest that solution [sup 31]P NMR spectroscopy of soil extracts be performed at 20°C. [ABSTRACT FROM AUTHOR]

Phytophthora agathidicida is the accepted causal agent of dieback in remnant stands of long‐lived indigenous New Zealand kauri (Agathis australis) and poses a significant threat to the long‐term survival of this species. Little is known about the effect of key soil physicochemical characteristics on the growth of P. agathidicida. In this study, we investigated the growth of P. agathidicida in soils collected from adjacent areas under original kauri forest, short rotation pine (Pinus radiata) plantation forest and grazed pastures. A growth response assay was used to quantify asexual (sporangia) and sexual (oospore) spore counts over 8 days in soils sampled from each land‐use. Significantly higher numbers of sporangia (p < 0.001) and oospores (p < 0.01) were found in pasture and pine forest soil within 2 days of the growth assay trials, suggesting these soils may favour asexual/sexual reproduction in the early stages of P. agathidicida establishment compared to kauri forest soils. Additionally, oospore production significantly increased over 8 days in pine forest soil, suggesting that with an increase in inoculum loads, these soils potentially act as pathogen reservoirs. The soil physicochemical properties (e.g., pH, C and N, phosphorus content and electrical conductivity) investigated in this study did not significantly correspond to spore count data between land‐uses, suggesting that differences in growth response are driven by other edaphic factors not explored in the present study. [ABSTRACT FROM AUTHOR]

Reduction of the potent greenhouse gas nitrous oxide (N(2)O) occurs in soil environments by the action of denitrifying bacteria possessing nitrous oxide reductase (N(2)OR), a dimeric copper (Cu)-dependent enzyme producing environmentally benign dinitrogen (N(2)). We examined the effects of increasing Cu concentrations on the transcription and activity of nitrite reductase (NIR), nitric oxide reductase (NOR) and N2 OR in Pseudomonas stutzeri grown anaerobically in solution over a 10-day period. Gas samples were taken on a daily basis and after 6 days, bacterial RNA was recovered to determine the expression of nirS, norB and nosZ encoding NIR, NOR and N(2)OR respectively. Results revealed that 0.05 mM Cu caused maximum conversion of N(2)O to N(2) via bacterial reduction of N(2)O. As soluble Cu generally makes up less than 0.001% of total soil Cu, extrapolation of 0.05 mg l(-l) soluble Cu would require soils to have a total concentration of Cu in the range of, 150-200 μg g(-1) to maximize the proportion of N(2)O reduced to N(2). Given that many intensively farmed agricultural soils are deficient in Cu in terms of plant nutrition, providing a sufficient concentration of biologically accessible Cu could provide a potentially useful microbial-based strategy of reducing agricultural N(2)O emissions., (© 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.)