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Background and aims: The intake of selenium, an essential element for animals and humans, in ruminants is largely determined by selenium concentration in ingested forages, which take up selenium mainly from soil. Ruminant excreta is a common source of organic fertilizer, which provides both nutrients and organic matter. This study aims to unentangle the unclear effect of applying different types of ruminant excreta in soils of different organic matter contents on selenium uptake by forage. Methods: Perennial ryegrass (Lolium perenne) was grown in soils of different organic matter contents. Urine and/or feces collected from sheep fed with organic or inorganic mineral supplements, including selenium, were applied to the soils. The selenium in the collected samples were analyzed using ICP-MS. The associated biogeochemical reactions were scrutinized by wet chemistry. Results: The application of urine and/or feces resulted in either the same or lower selenium concentrations in perennial ryegrass. The excreta type did not affect total selenium accumulation in grass grown in low organic matter soil, whereas in high organic matter soil, feces resulted in significantly lower total selenium accumulation than urine, which was attributed to a possible interaction of selenium sorption in soil and microbial reduction of Se. Conclusion: This one-time excreta application did not increase, but further decrease in some treatments, selenium concentration and accumulation in the perennial ryegrass. Consequently, to increase ruminant selenium intake, supplementing selenium directly to animals is more recommended than applying animal manure to soil, which might drive selenium reduction and decrease selenium uptake by grass. [ABSTRACT FROM AUTHOR]

Purpose: The incorporation of ryegrass (Lolium multiflorum Lam.; RG), a winter manure, could partly replace chemical N and reduce N loss during the succeeding rice seasons, but little is known about its impact on greenhouse gas emission. This study investigated the effect of different RG-urea substitution ratios (0% RG and 100% urea, 25% RG and 75% urea, 50% RG and 50% urea, 75% RG and 25% urea, 100% RG and 0% urea,) on net C and N mineralization, CH4 and N2O emissions in a paddy soil. Methods: Gas samples for CH4 and N2O fluxes were collected by using a closed chamber and determined by chromatograph method. Net C and N mineralization from the incorporated RG residue were tested by a mesh bag method. Results: Net C and N mineralization from RG followed a single exponential decay model, with 95.5%-97.8% of the original C and 98.7%-99.3% of N released during 192 days. The RG-urea substitution ratio increased CH4 emission, but was negatively correlated with N2O emission. In comparison with 0% substitution, global warming potential (GWP) and greenhouse gas intensity (GHGI) were not significantly different for the 25% and 50% RG substitutions, but were significantly higher for the 75% and 100% substitutions (P < 0.05). Soil redox, C and N remaining in litter residue were key characteristics explaining CH4 emission, while NH4+-N and NO3−-N were correlated with N2O emission. Conclusion: The increased GWP by CH4 emission after RG incorporation could be offset by N2O reduction when RG-urea substitution ratio was 50% or less. [ABSTRACT FROM AUTHOR]

Purpose : Nitrogen (N) transfer from white clover (Trifolium repens cv.) to ryegrass (Lolium perenne cv.) has the potential to meet ryegrass N requirements. This study aimed to quantify N transfer in a mixed pasture and investigate the influence of the microbial community and land management on N transfer. Methods: Split root 15N-labelling of clover quantified N transfer to ryegrass via exudation, microbial assimilation, decomposition, defoliation and soil biota. Incorporation into the microbial protein pool was determined using compound-specific 15N-stable isotope probing approaches. Results: N transfer to ryegrass and soil microbial protein in the model system was relatively small, with one-third arising from root exudation. N transfer to ryegrass increased with no microbial competition but soil microbes also increased N transfer via shoot decomposition. Addition of mycorrhizal fungi did not alter N transfer, due to the source-sink nature of this pathway, whilst weevil grazing on roots decreased microbial N transfer. N transfer was bidirectional, and comparable on a short-term scale. Conclusions: N transfer was low in a model young pasture established from soil from a permanent grassland with long-term N fertilisation. Root exudation and decomposition were major N transfer pathways. N transfer was influenced by soil biota (weevils, mycorrhizae) and land management (e.g. grazing). Previous land management and the role of the microbial community in N transfer must be considered when determining the potential for N transfer to ryegrass. [ABSTRACT FROM AUTHOR]

Aims: The aim of this work was to evaluate the fertilizing effect of three anaerobic co-digestates on the growth of the herbaceous plant Lolium rigidum. Methods: Nine treatments, combining different nutritional solutions (organic and inorganic) and number of fertilizations (one or two) were evaluated. Organic nutritive solution: plants grown with different olive mill solid waste (OMSW) -microalgae co-digestates: 75% OMSW-25% Raphidocelis subcapitata, volatile solids (VS) basis (OMSW-Rs); 50% OMSW- 50% Chlamydomonas Reinhardtii, VS basis (OMSW-Chl); and 75% OMSW-25% Secenedesmus quadricauda, VS basis (OMSW-Sq). Inorganic nutritive solution (INS): plants grown with inorganic Hoagland nutrient solution at 50%. After 60 days of experimentation, biometric and nutritional characteristics and photosynthetic activity were measured. Results: The results showed a favourable growth, development and nutritional quality of L. rigidum plants when digestates obtained from the anaerobic co-digestion of OMSW-microalgae are used as organic nutritional solutions as opposed to INS ones. The highest total biomass of L. rigidum was obtained with the treatments that involved two fertilizations. No inhibition due to excess nutrients was observed. A higher root/shoot ratio was achieved with the digestates of OMSW-Rs and OMSW-Ch as compared to that obtained with OMSW-Sq (F = 17.23 p ≤ 0.001). The nitrogen shoot biomass obtained after the organic treatments with the above-mentioned co-digestates was higher than that obtained after the inorganic treatment. Net photosynthesis rates did not present differences in the co-digestates treatments, being equal or superior to the INS treatments. Conclusions: The use of the anaerobic co-digestates from OMSW-microalgae can be considered a viable and promising alternative to inorganic fertilization. [ABSTRACT FROM AUTHOR]

Background and aims: Incorporation of biochar into the soil sequesters C for millennia, but the concomitant effects on plant rhizodepositions and nutrient (e.g., nitrogen; N) trade-offs via interactions of heterotrophic microbiota, might offset this sequestration. Methods: Ryegrass (Lolium perenne L.) with and without biochar amendment were pulse labelled in a 13CO2 atmosphere and 15N fertilizer added. Ryegrass and soils were destructively sampled at 16 and 30 days after seedling emergence. Isotope analysis was coupled with MiSeq sequencing of bacterial (16s rRNA) and fungal (ITS) genes to identify the effect of biochar on the associated microbiota involved in 13C allocation into soil aggregates and promotion of 15N uptake by L. perenne. Results: Biochar increased root biomass and 15N uptake but decreased rhizodeposited-13C recovery from large and small macroaggregates (by 12–57% and 57–72%, respectively). These changes in 13C flow and 15N uptake were accompanied by an increase in microbial biomass, and enhanced negative correlations between bacteria and fungi. O2PLS indicated members of seventeen genera that were correlated with soil stabilization of rhizodeposits in soil and plant N-uptake. For instance, Xanthomonadales (Proteobacteria) and RB41 (Acidobacteria), previously reported to be plant growth promoting rhizobacteria, were found to be positively correlated with 15N uptake by L. perenne. Conclusions: Our research explored the genera associated with biochar-modified 15N uptake by Lolium perenne and photosynthate 13C allocation into soil aggregates. Future research with SIP is required to fully assess microbial turnover, the ubiquity of similar rhizosphere microbiota and their fundamental importance for sequestration in the plant-soil-microbe-biochar systems. [ABSTRACT FROM AUTHOR]

Aims: An Italian ryegrass cultivar (Lolium multiflorum Lam. cv. Bb2067), selected and bred for increased leaf magnesium (Mg) concentration in the 1970s, reduced the incidence of hypomagnesaemia in sheep under experimental grazings. Here, we report evidence from archival experiments showing that cv. Bb2067 had consistently greater Mg concentrations at multiple sites. We also aimed to quantify variation in leaf Mg concentration among modern perennial ryegrass (Lolium perenne L.), hybrid ryegrass (Lolium perenne × multiflorum), and tall fescue (Festuca arundinacea Shreb.) cultivars. Methods: Data are reported from unpublished 1980s field-plot experiments for cv. Bb2067 and contemporaneous reference cultivars, sown at two UK locations in 1983 and 1984, and from 397 cultivars of modern forage grass in 13 UK-based breeding experiments sampled in spring 2013. Results: Across sites, years and cuts, cv. Bb2067 had a consistently greater leaf Mg concentration and lower potassium (K) concentration and forage tetany index (FTI) than reference cultivars in the 1980s experiments. Seasonal variation in leaf Mg and K concentrations and FTI were observed in the 1980s experiments, with K concentrations being generally greatest and Mg concentrations smallest in spring. Among modern forage grasses, there was large variation in leaf Mg concentration (up to 6.3-fold) and FTI (up to 2.1-fold), both within and between species, which varied independently of yield. Among a subset of hybrid ryegrass cultivars, there is evidence that the high Mg trait is already present in some modern breeding lines, albeit previously unreported. Conclusions: The variation in leaf Mg concentration and FTI among old and new cultivars shows there is considerable potential to breed forages with improved mineral quality to improve livestock health, potentially without compromising yield or other nutritional traits. [ABSTRACT FROM AUTHOR]

Background and aims: Interactions between functional groups of soil fauna and plants are poorly explored although they drive functional processes such as nutrient availability and therefore plant performance. Here, we investigated the separated and combined effects of two collembolan functional groups on soil properties and growth of Lolium perenne, a typical grass species from temperate grasslands. Methods: Under microcosm conditions, we established four treatments based on the presence and combination of two collembolan functional groups: (1) control without Collembola; (2) epedaphic species; (3) euedaphic species; (4) epedaphic + euedaphic species. After five months of experiment, we measured the effect of those treatments on both nutritional and morphological variables of L. perenne and on soil properties. Results: Collembolan presence stimulated plant performance. Individuals of L. perenne growing with euedaphic species presented higher numbers of leaves and nutrient contents compared with individuals growing with epedaphic species. Further, the combination of both collembolan functional groups enhanced plant performance and soil nutrient availability, demonstrating that a functionally diversified soil fauna assemblage cause overyielding of ecological processes. Conclusion: Our results provide evidences of complementarity interactions between different functional groups of soil fauna causing overyielding of primary production. [ABSTRACT FROM AUTHOR]

Background and aims: Low temperature stress is a common hazard during plant growth. Endophyte infection has been shown to increase cold tolerance in host plants. Many Lolium perenne cultivars contain low to moderate levels of endophyte. This study was done to explore cultivar improvement by segregation of endophyte containing individuals from the original cultivar to create a high endophyte subpopulation. Methods: Endophyte-infected plants were segregated over the first 3 years to produce high-endophyte subpopulation, and field and greenhouse experiments were carried out in the forth and fifth to determine the cold tolerance of the L. perenne subpopulation with high endophyte infection rates (N), the parent (F), the control endophyte-free subpopulation (E) and the control local variety (L). Results: (1) After 3 years of screening, high endophyte infection rates in the tillers and seeds of plants were still observed (96.5%), and agronomic traits (crown width, plant height, panicle number, withering, regreen-up, the growth cycle and the over-wintering rate) was also improved with increased Epichloë colonization of host plant. (2) The subpopulation with high endophyte infection rates and improved agronomic traits had better cold tolerance than the parent, the control endophyte-free subpopulation and the control local variety. The possible mechanisms by which high endophyte infection enhances cold resistance in the field include increased root system, increased the over-wintering rate, reduced regrowth periods with the sowing date being October 15th. (3) The high-endophyte subpopulation significantly increased SOD, POD, CAT, and APX activities at 0, 5, and 10 °C by 11.8%–44.6%, compared with the parent population. Conclusions: The subpopulation had a high endophyte infection rate, improved agronomic traits and higher enzymatic activities. These results indicate that increasing endophyte infection rates by selection, effectively improved agronomic traits and cold tolerance. [ABSTRACT FROM AUTHOR]

Aims: Deep-rooted agricultural crops can potentially utilize deep soil moisture to reduce periods where growth is water limited. Chicory (Cichorium intybus L.) is a deep-rooted species, but the benefits of deep roots to water uptake has not been studied. The aim of this study was to investigate the value of deep roots (>2 m) under topsoil water limitation. Methods: Chicory grown in 4 m deep soil-filled rhizotrons was exposed to either topsoil drought or resource competition from the shallow-rooted species ryegrass (Lolium perenne L.) and black medic (Medicago lupulina L.). The effect on deep water uptake was assessed using non-destructive measurements of roots, soil water and tracers. Results: Water uptake occurred below 1.7 m depth in 2016, and below 2.3 m depth in 2017 and contributed significantly to chicory water use. However, neither surface soil drying nor intercropping increased deep water uptake to relieve water deficit in the shoots. Conclusion: Chicory benefits from deep-roots during drought events, as it acceses deep soil moisture unavailable to more shallow rooted species, yet deep water uptake was unable to compensate for the reduced topsoil water uptake due to soil drying or crop competition. [ABSTRACT FROM AUTHOR]

Aims: We tested if chicory acquires nutrients from soil layers down to 3.5 m depth and whether the deep nutrient uptake increases as a result of drought or intercropping with ryegrass and black medic. We also tested whether application of the trace elements Cs, Li, Rb, Sr and Se, as tracers, result in similar uptake rates. Methods: The methodological tests were carried out in a pilot experiment where the tracers were applied to 1 m depth in lucerne and red beet grown in tube rhizotrons. The dynamics of deep nutrient uptake in chicory was studied in large 4 m deep rhizoboxes. A drought was induced when roots had reached around 2 m depth. Results: Chicory acquired 15N from 3.5 m depth and trace element tracers from 2.3 m depth. We found no compensatory tracer uptake with depth during drought. We found some indications of a compensatory tracer uptake from 2.3 and 2.9 m depth in intercropped chicory. Application of equimolar amounts of trace elements resulted in similar excess tracer concentrations within species. Conclusion: Chicory demonstrates nutrient uptake from below 3 m but does not increase deep nutrient uptake as a response to limited topsoil nutrient availability induced by drought or intercropping. [ABSTRACT FROM AUTHOR]

Aims: Roots are vital organs for plants, but the assessment of root traits is difficult, particularly in deep soil layers under natural field conditions. A popular technique to investigate root growth under field or semi-field conditions is the use of minirhizotrons. However, the subsequent manual quantification process is time-consuming and prone to error. Methods: We developed a multispectral minirhizotron imaging system and a subsequent image analysis strategy for automated root detection. Five wavelengths in the visible (VIS) and near-infrared (NIR) spectrum are used to enhance living roots by a multivariate grouping of pixels based on differences in reflectance; background noise is suppressed by a vesselness enhancement filter. The system was tested against manual analysis of grid intersections for both spring barley (Hordeum vulgare L.) and perennial ryegrass (Lolium perenne L.) cultivars at two time-points. The images of living roots were captured in wet subsoil conditions with dead roots present from a previous crop. Results: Under the soil conditions used in the study, NIR reflectance (940 nm), provided limited ability to separate between rhizosphere components, compared to reflectance in the violet and blue light spectrum (405 nm and 450 nm). Multivariate image analysis of the spectral data, combined with vesselness enhancement and thresholding allowed for automated detection of living roots. Automated image analysis largely replicated the root intensity found during manual grid intersect analysis of the same images. Although some misclassification occurred, caused by elongated structures of dew and chalkstone with similar reflectance pattern as living root, the system provided similar or in some cases improved detection of genotypic differences in the total root length within each tube. Conclusion: The multispectral imaging system allows for automated detection of living roots in minirhizotron studies. The system requires considerably less time than traditional manual recording using grid intersections. The flexible training strategy used for root segmentation offers hope for the transfer to other rhizosphere components and other soil types of interest. [ABSTRACT FROM AUTHOR]

Background and aims: Microbial denitrification is the primary driver of nitrogen losses from the plant-soil system and the key process for the closure of the global N cycle. All major controls of denitrification might be directly or indirectly affected by plants. However, there is a lack of research of the direct effects of plants on soil denitrification and how this effect might be mediated by soil properties. This study assesses the effect of three common crop species and two agricultural soils on denitrification potentials. Methods: We conducted a factorial experiment under controlled conditions to analyze the effects of (1) different plant species (barley, wheat or ryegrass), (2) two different soils (texture/ SOC) and (3) two different soil moisture levels on Denitrification Enzyme Activity (DEA) in bulk and rhizosphere soil. Results: The SOC richer clay loam soil showed on average higher DEA (+81%) compared to the SOC poorer silty loam soil. All three plants were found to stimulate denitrification with significant differences between certain species: rye grass (+92% ± 14%) ≥ barley (+75% ± 26%) ≥ wheat (+50% ± 19%). Conclusions: DEA in agricultural soils is interactively controlled by plant species and soil type with an overall stimulating effect of plants on the denitrification potential. Future research should focus on disentangling single mechanisms of plant control on actual denitrification rates and N gas product ratios. [ABSTRACT FROM AUTHOR]

Aims: Belowground legume nitrogen (N) composed of roots and rhizodeposition is an important N input to soils, but published data of belowground N vary broadly, probably due to extrapolation from short-term experiments and dissimilar growing conditions. We quantified belowground N inputs of red clover (Trifolium pratense L.) during two consecutive years in a clover-grass sward along a soil nutrient availability gradient.Methods: We established a red clover-perennial ryegrass (Lolium perenne L.) model sward in microplots located in field plots of the DOK experiment, which has a 33-year history of organic and conventional cropping, resulting in a soil nutrient availability gradient. Four treatments were examined: the zero fertilisation control, bio-organic with half and full dose manure application, and the conventional system with mineral fertilisation at full dose. We studied the development of clover aboveground and belowground N using multiple pulse 15N urea leaf labelling.Results: Belowground clover N increased over time and with rising nutrient availability and was proportional to aboveground clover N at all times. Belowground clover N amounted to 40% of aboveground clover N during two consecutive years, irrespective of the nutrient availability status. Belowground clover N development was initially dominated by fast root growth, followed by enhanced root turnover during the second year. Potassium availability limited clover growth and total N accumulation in treatments with low nutrient availability.Conclusions: Belowground red clover N inputs could be estimated from aboveground N by a constant factor of 0.4, regardless of the nutrient availability and cultivation time. Root turnover led to a distinct absolute increase of N rhizodeposition over time. Hence, N rhizodeposition, with an 80% share of belowground N, was the predominant N pool at the end of the second year. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the efficiency of acidified (to pH 5.5) and dried digestate solids as a fertilization product in a pot experiment with ryegrass. Methods: The NH-N pool of the solids was labelled with N prior to acidification and drying to estimate plant N uptake efficiency. The effect of digestate solids on plant growth and N and P uptake was compared to the effect of different mineral N-P fertilization combinations. Results: Non-acidified dried digestate solids showed inferior N fertilization performance compared to their raw and acidified counterparts, and higher drying temperature reduced solids N mineralization. More than 40% of the NH-N in the raw, raw acidified and acidified dried solids treatments was recovered by the ryegrass over 5-months, similar to recovery with medium mineral N rates, resulting in mineral fertilizer equivalency of 32-41%. Digestate solids treatment altered the water extractable P of the solids, but less so the ryegrass P uptake, mainly due to the buffer capacity of the soil. However, ryegrass P uptake in non-acidified dried solids treatments was probably inhibited by poor growth due to low N availability. Conclusions: Acidification of digestate solids prior to drying may be an important treatment to maintain the solids fertilizing value while enhancing its manageability. [ABSTRACT FROM AUTHOR]

Background and aims: Nitrogen balances are useful tools to increase our understanding of soil N processes and the efficiency of plants in taking up animal urine-N. This study aimed to investigate the effect of forage type on the fate of autumn-applied urine-N (700 kg N ha). Methods: In a 17-month lysimeter study the recoveries of N in herbage, leachate, nitrous oxide, and soil + roots (at the end of the trial) were determined for three forage types: perennial ryegrass-white clover (RGWC, Lolium perenne L. -Trifolium repens L.), Italian ryegrass (Italian RG, Lolium multiflorum Lam.), and lucerne ( Medicago sativa L.) under simulated autumn grazing. Results: We recovered 81.5-85.5% of the N applied in the urine. Italian RG had the greatest amount of urine-N recovered in the herbage (49.5%) and the least recovered in leachate (16.8%) making it the most efficient of the three forages for utilizing urine-N. For RGWC, herbage and leachate recoveries were 40.1% and 23.7% , respectively. Lucerne was the least efficient with recoveries of N in herbage and leachate equaling 18.4% and 52.5%, respectively. Conclusions: This study demonstrates that Italian ryegrass could offer benefits in reducing urine-N leaching losses through its ability to take up more urine-N over winter. [ABSTRACT FROM AUTHOR]

Background and aims: There is substantial evidence that legume-derived Nitrogen (N) is transferred to neighboring non-legumes in grassland mixtures. However, there is sparse information about how deep rooted non-legume forage herbs (forbs) influence N transfer in multi-species grasslands. Methodology: Red clover ( Trifolium pretense L.) was grown together with perennial ryegrass ( Lolium perenne L.) and one of three forb species: chicory ( Cichorium intybus L.), ribwort plantain ( Plantago lanceolata L.) or caraway ( Carum carvi L.) in a field experiment. During the first year after the establishment, red clover leaves were labeled with N-urea to determine the N transfer from red clover to companion ryegrass and forbs. Results: On an annual basis, up to 15 % of red clover N was transferred to the companion ryegrass and forbs, but predominantly to the grass. The forb species did not differ in their ability to take up clover N, but biomass production and soil N acquisition was higher in chicory and plantain than in caraway. Conclusions: Grass relied to a great extent on clover N, whereas forbs relied on soil N. Soil N-enrichment indicated that N transfer occurred in the upper soil layers and that a dependence on clover-derived N did not necessarily give grass a growth advantage. [ABSTRACT FROM AUTHOR]

Aims: Increasing the input and turnover of root tissue is considered to be one method that may increase carbon (C) inputs and storage in soil. The use of herbicide during pasture renewal (periodic re-sowing of pasture) is expected to increase root inputs and turnover as plants die. The objective of this study was to quantify the short-term impact of pasture renewal on root turnover and C input to soil of ryegrass-clover pastures. Methods: Pastures were labelled in the field using a C isotope pulse labelling method within 1 m clear chambers. Five daily labelling events were carried out during one week in paired treatment plots within 3 replicate paddocks. One plot per paddock was sprayed with herbicide and then the pasture was renewed by direct drilling of seed. The C of roots and soil (0-100 mm) was measured at regular intervals over an 89-day period. Results: Herbicide application caused an initial rapid turnover time of 17 days followed by a slower turnover time of 524 days, compared to unsprayed pasture which had a root turnover of 585 days. Faster root turnover following herbicide application resulted in greater cumulative C input to soil over 89 days with approximately double the C input in the sprayed treatment (3238 ± 378 kg C ha) compared to the unsprayed treatment (1726 ± 540 kg C ha). Conclusions: The use of glyphosate during pasture renewal increased root turnover and resulted in a greater short term cumulative C input to soil. This study provides the first values of root turnover and C input to soil during a pasture renewal event in New Zealand pasture systems and contributes to the understanding of how pasture roots may influence the soil C input following plant death in grassland systems. [ABSTRACT FROM AUTHOR]

Aim: A principal goal of grassland management is to minimize the use of artificial fertilizers by maximising the productivity of nitrogen-fixing leguminous plants such as clovers. The objective of this study was to investigate whether a plant-growth-promoting strain of the free-living rhizosphere fungus Trichoderma hamatum (GD12) could be used as a natural and sustainable means of enhancing the competitiveness of white clover ( Trifolium repens) while allowing increased productivity of both clover and ryegrass ( Lolium perenne) in mixed species systems. Methods: An assay was conducted in rhizotrons with white clover and ryegrass sown alone and in mixture and in soils inoculated and non-inoculated with GD12. Plant height, growing rate, phenological stage, number of Rhizobium nodules and biomass were assessed. A histological study of Rhizobium nodules and a stable isotopes analysis was conducted to determine the N fixation capacity of white clover. Results: When introduced as a soil inoculant, the fungus increased biomass production of both plant species and shortened their phenological cycles. Furthermore, in clover, GD12 enhanced plant height and growth rate and stimulated Rhizobium nodulation, while N stable isotope analysis demonstrated increased N fixation. Conclusion: This shows that soil amendment with a beneficial strain of saprotrophic fungus bestows a competitive advantage to white clover in clover-ryegrass mixtures and provides a sustainable mechanism for improving the mixture productivity. [ABSTRACT FROM AUTHOR]

Background and aims: Plant uptake of active pharmaceutical ingredients (APIs) is increasingly leading to concerns about their potential exposure to humans and wildlife via dietary intake. Due to the extraordinary ability of biochars to bind organic compounds, plant uptake experiments were conducted to assess the effect of soil-amendment of three different biochars on the uptake of APIs from spiked soil. Methods: Pot experiments were undertaken to assess the extent of sorption and corresponding bioaccessibility of two APIs (carbamazepine - CBZ and propranolol -PRL) to ryegrass ( Lolium perenne) grown in an API-spiked loamy sand, with and without biochar amendment (5 t/ha equivalent). The soil was amended with three different biochars produced from eucalyptus wood and wheat residues. Results: Both APIs were taken up by ryegrass, with CBZ preferentially accumulated (14.3 mg/kg CBZ, 3.8 mg/kg PRL in unamended soil) due to its comparatively high concentration in porewater. Soil amendment with biochars increased partitioning of the two APIs by up to three- fold, with corresponding decreases in porewater (34-72 % of unamended soil) and plant tissue (17-64 %) concentrations. Conclusions: Biochars were effective in reducing the uptake of APIs into plant tissues from a contaminated soil and may be effective in the management of API residues in contaminated soils. [ABSTRACT FROM AUTHOR]

Background and aims: A strategy to increase soil C under pasture-based systems is to increase the root mass inputs or increase rooting depth of plants. Our objective in this study was to measure the seasonal dynamics of root mass and C inputs under two different pasture types (ryegrass-clover vs moderately diverse) that differ in plant diversity and which are commonly used in New Zealand agriculture. Methods: This study was carried out on an existing plant diversity field trial containing six replicate paddocks of both moderately-diverse and ryegrass-clover pastures. Soil cores (0-100-200-300 mm sections) were collected seasonally across 1 year and individual root traits assessed from all species. Results: The moderately diverse pasture had greater root mass (5320-9350 kg ha) than the ryegrass-clover pasture (3810-5700 kg ha) for all seasons and had greater root mass lower in the soil profile. A secondary objective demostrated no significant difference in root mass between high and low sugar ryegrass cultivar. Increased root mass results in an estimated increase of C input to the soil of about 1203 kg C ha (0-300 mm depth) under the moderately diverse pasture, excluding root exudates. Root trait measurements demonstrated a greater diversity of root traits in the moderately diverse sward compared to the ryegrass-clover pasture. Conclusions: Moderately diverse pasture systems offer scope to increase soil C under grazed pastures through increased root mass inputs and rooting depth. [ABSTRACT FROM AUTHOR]

Aims: The objectives of this study were to compare techniques for measuring biological nitrogen fixation (BNF) and to assess how fertiliser N input affects the balance between BNF and sustainable herbage production on perennial ryegrass ( Lolium perenne L.)/white clover ( Trifolium repens L.) grassland. Methods: Biological N fixation and herbage production by white clover based grassland was measured in 2011 and 2012 under four nominal annual fertiliser N inputs: 0 (0N), 86 (86N), 140 (140N) and 280 kg ha (280N). Biological N fixation was measured using the N isotope dilution and N natural abundance techniques under all fertiliser N inputs and also using the nitrogen difference technique under 0N. Results: The two N techniques produced similar annual estimates of above-ground BNF across the range of fertiliser N inputs. Fertiliser N input resulted in higher herbage dry matter yield, but reduced annual BNF which averaged 80, 64, 66 and 47 kg ha on 0N, 86N, 140N and 280N, respectively, across both techniques and years. Conclusions: The two N techniques were comparable in estimating BNF. Intermediate fertiliser N inputs achieved a balance between minimising detrimental impact on BNF and potential N loss while producing more herbage DM yield than clover swards receiving no fertiliser N. [ABSTRACT FROM AUTHOR]