Effect of using conventional and controlled release fertiliser on nutrient runoff from various vegetated roof systems

Extensive vegetated roofs are becoming popular as a way to improve the environmental quality of cities. As more vegetated roofs are installed, there is a need for knowledge pertaining to maintenance and impact vegetated roofs have on stormwater quality. Our study investigated nutrient runoff, substrate nutrient storage and plant uptake following fertilisation of vegetation mats, shoot-established vegetation systems and unvegetated substrate using three levels of fertiliser applied as either controlled release fertiliser (CRF), or as a combination of CRF and conventional fertiliser. Conventional fertilisers caused high nutrient concentrations in the runoff water. Concentrations decreased during the duration of the experiment but at the end of the experiment they were still higher than after fertilisation with CRF. Conventional fertiliser also increased the total nutrient runoff. Vegetation system type influenced nutrient runoff and fertilisation of old vegetation mats reduced the risk for nutrient leaching compared to fertilisation of newly established surfaces. This can be attributed to temporary storage in substrate and increased uptake by vegetation. The temporary storage of nutrients following fertilisation indicated that there might be a risk for prolonged leaching. Thus, addition of conventional fertilisers or nutrient-rich material during production can reduce stormwater quality.     

Biomass production and nutrient accumulation in <Emphasis Type="Italic">Sparganium emersum</Emphasis> Rehm. after sediment treatment with mineral and organic fertilisers in three mesocosm experiments

The response of the aquatic plant Sparganium emersum to different sediment nutrient levels was studied in three mesocosm experiments. The aim was to assess plant growth parameters and nutrient accumulation in the plant tissue under conditions relevant for habitats with sediments affected by anthropogenic nutrient enrichment. The experimental treatments were produced by fertilisation of the rooting medium (washed river sand) with differing doses of either NPK mineral fertiliser or digested sludge from solid pig slurry waste. Growth inhibition by high nutrient levels was not observed in any treatment (highest nutrient concentrations in the sediment with mineral fertiliser: N 250 mg kg⁻¹, P 50 mg kg⁻¹; organic fertiliser: N 6300 mg kg⁻¹, P 1800 mg kg⁻¹), which confirms the tolerance of S. emersum to high nutrient loads. The sediment nutrient concentration was best reflected in shoot dry mass. Nutrient contents in plant tissues were similar for most nutrient concentrations in the rooting media; only N increased significantly with N levels in the sediment in belowground parts. Nutrient standing stocks in plants, however, generally corresponded to the nutrient supply, and reached highest values (max. N 3.7 g m⁻², P 1.2 g m⁻²) in the richest treatments with organic fertiliser. The capability of S. emersum to use nutrients from high sediment concentrations and in organically polluted environments recommends this species for use in water quality management including tertiary wastewater treatment.     

Manure application improves both bumblebee flower visitation and crop yield in intensive farmland

Pollinators provide vital ecosystem services across croplands, yet simultaneously they are influenced by agricultural practices. Nevertheless, only a few studies have explored the potential interactions between soil fertilisers and pollinators. The aim of the current study, which was carried out in Poland in 2015, was to investigate the effect of different fertiliser regimes on bumblebee flower visitation rate and seed yield in crops of the field bean (Vicia faba L.). Our results show that the number of bumblebee visits may be affected by the choice of crop fertiliser. We detected differences in bumblebee number between fertiliser treatments. The organic fertiliser (manure) treatment resulted in the highest bumblebee visitation, although this did not differ significantly from NP, no fertiliser and NK treatments. On the other hand, we observed lower numbers of bumblebees on field bean plots treated with N, NPK, and PK inorganic fertilisers. Manure application also boosted plant height and resulted in a high yield similar to other balanced fertilisers (NPK and PK). Therefore, manure was the only fertiliser that resulted in a high field bean yield and at the same time attracted the main pollinators of the crop. Thus, we suggest that appropriate management practices influence both plant growth and also pollination services and we show that modern agriculture can make compromise between effectiveness and nature conservation.     

Effect of nitrogen and phosphorus concentration on their removal kinetic in treated urban wastewater by Chlorella vulgaris

This study evaluates the feasibility of removing nutrients by the microalgae Chlorella vulgaris, using urban wastewater as culture medium, namely the effluent subjected to secondary biological treatment in a wastewater treatment plant (WWTP). For this, laboratory experiments were performed in batch cultures to study the effect of initial nitrogen and phosphorus concentrations on growth and reduction of nutrient performance of C. vulgaris. The microalga was cultivated in enriched wastewater containing different phosphorus (1.3-143.5 mg x L(-1) P.PO4(3-)), ammonium (5.8-226.8 mg x L(-1) N-NH4+) and nitrate (1.5-198.3 mg x L(-1) N-NO3-) concentrations. The nutrient removal and growth kinetics have been studied: maximum productivity of 0.95 g SS x L(-1) x day(-1), minimum yield factor for cells on substrate (Y) of 11.51 g cells x g nitrogen(-1) and 0.04 g cells x g phosphorus(-1) were observed. The results suggested that C. vulgaris has a high potential to reduce nutrients in secondary WWTP effluents.     

Identifying Amsterdam's nutrient hotspots: A new method to map human excreta at building and neighborhood scale

Recovering nutrients from human excreta and wastewater has been receiving increasing attention as a means to supplement or replace synthetic fertilizer production. Apart from technologies for nutrient recovery at centralized wastewater treatment plants, numerous decentralized, source‐separated sanitation systems, also known as new sanitation systems, have been developed to facilitate recovery. Decision‐making for the planning and implementation of new sanitation systems would benefit from a spatially explicit inventory of nutrient hotspots in urban areas. To provide visual representations of nutrient loads, we developed a methodology that combines spatial‐temporal modeling with geographic information system analysis, and used it for the city of Amsterdam. The methodology is new in the field of nutrient mapping, especially at the smallest geographical scale: building. Nitrogen, phosphorus, and potassium loads and hotspots are mapped at both building and neighborhood scale, drawing attention to the need for multiple scale analyses in decision‐making. This study concludes with a discussion on the potential to further develop the method proposed to include more detailed and verified data and to identify nutrient hotspots that are promising as nutrient recovery sites with new sanitation systems.     

Biomass allocation and nutrient use in fast-growing woody and herbaceous perennials used for phytoremediation

This study assessed the suitability of two deciduous woody perennials (Salix spp. and Populus spp.) and two summer green herbaceous perennials (Phragmites australis and Urtica dioica) for purification of nutrient enriched wastewater. The main hypothesis tested was that species with a particular trait combination of high relative growth rate (RGR), low nutrient productivity (A) and high mean residence time (MRT) of nutrients would be most effective in accumulating nutrients. The nitrogen and phosphorus use efficiency at the whole plant level was analysed. Four treatments comprising two possible phytoremediation substrates (municipal wastewater and landfill leachate) and two control plant nutrition situations (balanced nutrient solution and pure water) were applied in four replications to the four plant species. Generally, all four species studied showed a high RGR and a low P productivity in the balanced nutrient solution treatment, while the opposite (low RGR and high P productivity) was seen in the phytoremediation substrate and pure water treatments. The general conclusion is that if P is present in marginal proportions in the wastewater, a vegetation filter with Phragmites would have an advantage since biomass and nutrient accumulation in Phragmites does not decrease as much during phytoremediation as that in deciduous woody perennials.     

Agro-industrial waste materials and wastewater sludge for rhizobial inoculant production: a review

Inoculating legumes with commercial rhizobial inoculants is a common agriculture practice. Generally, inoculants are sold in liquid or in solid forms (mixed with carrier). The production of inoculants involves a step in which a high number of cells are produced, followed by the product formulation. This process is largely governed by the cost related to the medium used for rhizobial growth and by the availability of a carrier source (peat) for production of solid inoculant. Some industrial and agricultural by-products (e.g. cheese whey, malt sprouts) contain growth factors such as nitrogen and carbon, which can support growth of rhizobia. Other agro-industrial wastes (e.g. plant compost, filtermud, fly-ash) can be used as a carrier for rhizobial inoculant. More recently, wastewater sludge, a worldwide recyclable waste, has shown good potential for inoculant production as a growth medium and as a carrier (dehydrated sludge). Sludge usually contains nutrient elements at concentrations sufficient to sustain rhizobial growth and heavy metals are usually below the recommended level. In some cases, growth conditions can be optimized by a sludge pre-treatment or by the addition of nutrients. Inoculants produced in wastewater sludge are efficient for nodulation and nitrogen fixation with legumes as compared to standard inoculants. This new approach described in this review offers a safe environmental alternative for both waste treatment/disposal and inoculant production.     

Life cycle inventory practices for major nitrogen,phosphorus and carbon flows in wastewater and sludge management systems

Purpose

Nitrogen, phosphorus and carbon originating from wastewater and sludge can, depending on their partitioning during wastewater treatment, either become available as potential resources or leave as emissions. Several reviews have highlighted the dependence of life cycle assessment (LCA) results on the inventory data. To provide a foundation for future assessments of systems in which resources are utilised from wastewater or sludge, this paper identifies common practice and highlights deficiencies in the selection and quantification of nitrogen, phosphorus and carbon containing flows.

Methods

Inventories of major direct flows containing nitrogen, phosphorus and carbon in 62 studies on wastewater and sludge management operations have been reviewed. A special focus was put on flows of nitrogen, phosphorus and carbon originating from the wastewater and sludge and on how these are either leaving the system as emissions and hereby contributing to environmental impacts, or how potential resource flows of these elements are accounted for, in particular when sludge is used in agriculture.

Results and discussion

The current study shows a large variation between studies regarding what resource and emission flows were included in inventories on wastewater and sludge treatment, the type of data used (primary or secondary data) and, when flows have been modelled rather than measured, how the modelling has been done. Except for nitrogen and phosphorus emissions via the effluent, which were generally quantified using measured data or data modelled to represent the specific situation, direct emissions to air from the water and sludge lines at the wastewater treatment plant were mostly estimated using secondary data, sometimes of poor data quality. In systems where resources were recovered through agricultural application of sludge, studies often credited the system for avoided use of mineral fertiliser, but the considered replacement ratio differed.

Conclusions

The current review identified increased completeness and specificity in the modelling of the evaluated flows as particularly relevant for future studies and highlighted a need for improved transparency of data inventories. The review can be used as a support for LCA analysts in future studies, providing an inventory of common practices and pinpointing deficiencies, and can thereby support more conscious and well-motivated choices as regard which flows to include in assessments and on the quantification of these flows.

     

Plant–microbes interactions in enhanced fertilizer-use efficiency

The continued use of chemical fertilizers and manures for enhanced soil fertility and crop productivity often results in unexpected harmful environmental effects, including leaching of nitrate into ground water, surface run-off of phosphorus and nitrogen run-off, and eutrophication of aquatic ecosystems. Integrated nutrient management systems are needed to maintain agricultural productivity and protect the environment. Microbial inoculants are promising components of such management systems. This review is a critical summary of the efforts in using microbial inoculants, including plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi for increasing the use efficiency of fertilizers. Studies with microbial inoculants and nutrients have demonstrated that some inoculants can improve plant uptake of nutrients and thereby increase the use efficiency of applied chemical fertilizers and manures. These proofs of concept studies will serve as the basis for vigorous future research into integrated nutrient management in agriculture.     

Past, present and future of organic nutrients

Background

Slowing crop yield increases despite high fertiliser application rates, declining soil health and off-site pollution are testimony that many bioproduction systems require innovative nutrient supply strategies. One avenue is a greater contribution of organic compounds as nutrient sources for crops. That plants take up and metabolise organic molecules (‘organic nutrients’) has been discovered prior to more recent interest with scientific roots reaching far into the 19th century. Research on organic nutrients continued in the early decades of the 20th century, but after two world wars and yield increases achieved with mineral and synthetic fertilisers, a smooth continuation of the research was not to be expected, and we find major gaps in the transmission of methods and knowledge.

Scope

Addressing the antagonism of ‘organicists’ and ‘mineralists’ in plant nutrition, we illustrate how the focus of crop nutrition has shifted from organic to inorganic nutrients. We discuss reasons and provide evidence for a role of organic compounds as nutrients and signalling agents.

Conclusion

After decades of focussing on inorganic nutrients, perspectives have greatly widened again. As has occurred before in agricultural history, science has to validate agronomic practises. We argue that a framework that views plants as mixotrophs with an inherent ability to use organic nutrients, via direct uptake or aided by exoenzyme-mediated degradation, will transform nutrient management and crop breeding to complement inorganic and synthetic fertilisers with organic nutrients.     

A probabilistic framework for nutrient uptake length

The nutrient uptake length, the average displacement of a nutrient in a stream before being taken up by the biota, is an important quantity to characterize and compare streams and rivers, or to quantify certain aspects of their related ecosystems. This concept has been widely used for almost 30 years now, and uptake lengths have been estimated for several nutrients in many systems, but it also suffers from a number of limitations, one of them being the requirement of a spatially homogeneous stream or river. We combine recently advocated, transport-based models of stream processes with current concepts of dispersal theory into a novel framework for nutrient uptake length. The framework is based on the theory for dispersal kernels in terrestrial systems, where the entire distribution of dispersal distances is calculated and not only the average. Within this framework, we can re-derive all previous results and formulae for uptake length, and we can include spatially heterogeneous stream environments. In addition, we propose a number of new characteristic quantities that can complement nutrient uptake length when evaluating the health of a stream system or the impact of a source of nutrients. We illustrate our method with two examples of spatially non-homogeneous streams: point-source input of nutrients (e.g., wastewater treatment plant) and diffuse lateral input (e.g., agricultural run-off), and we show how to measure the relative contribution of the two sources to the uptake length and other characteristics.     

Nutrient availability and maize growth in a soil amended with earthworm casts from a South African indigenous species

The study was undertaken to assess the availability to maize of nutrients from earthworm casts (wormcasts) collected from a grazing paddock in the Eastern Cape province of South Africa. Maize (cv PAN 473) was grown in pots filled with ground wormcasts, non-casted surrounding soil and a mixture of the two media. Fertiliser application increased growth and uptake of nutrients by maize grown on both wormcast and non-casted soil. Maize grown on wormcasts had significantly (p < 0.05) higher plant height, stem diameter, dry weight and showed higher nutrient uptake and lower fertiliser response than that grown on corresponding non-casted surface soil. The uptakes of plant nutrients, growth and dry matter yields were in the order fertiliser>wormcasts>non-casted soil. Mixing worm casts with non-casted soil improved maize growth and nutrient uptake over non-casted soil. It is concluded that wormcasts could be used as a soil amendment for crop production, especially in small-scale production systems.     

Kinetic exploration of nitrate-accumulating microalgae for nutrient recovery

Within sustainable resource management, the recovery of nitrogen and phosphorus nutrients from waste streams is becoming increasingly important. Although the use of microalgae has been described extensively in environmental biotechnology, the potential of nitrate-accumulating microalgae for nutrient recovery has not been investigated yet. The ability of these marine microorganisms to concentrate environmental nitrate within their biomass is remarkable. The aim of this study was to investigate the application potential of nitrate-accumulating diatoms for nutrient recovery from marine wastewaters. The intracellular nitrate storage capacity was quantified for six marine diatom strains in synthetic wastewater. Amphora coffeaeformis and Phaeodactylum tricornutum stored the highest amount of nitrate with respectively 3.15 and 2.10 g N L^?1 of cell volume, which accounted for 17.3 and 4.6 %, respectively, of the total nitrogen content. The growth and nitrate and phosphate uptake of both diatoms were further analyzed and based on these features P. tricornutum showed the highest potential for nutrient recovery. A mathematical model was developed which included intracellular nitrate storage and the kinetic parameters were derived for P. tricornutum. Furthermore, a simulation study was performed to compare the performance of a proposed microalgal nutrient recovery unit with a conventional denitrification system for marine wastewater treatment. Overall, this study demonstrates the potential application of P. tricornutum for saline wastewater treatment with concurrent nitrogen and phosphorus recycling.     

Characterisation of the type and extent of nutrient limitation in grassland vegetation using a bioassay with intact sods

An important methodological problem in plant ecology concerns the way in which the type and extent of nutrient limitation in terrestrial communities should be assessed. Conclusions on nutrient limitation have been founded mainly on soil extractions, fertiliser trials and tissue nutrient concentrations. In order to avoid some of the problems associated with these methods, we employed a special technique using intact sods which rooted both in the intact soil and in a nutrient solution, from which N, P and K were omitted stepwise. The method was applied to hay-field communities which differed in their history of fertiliser application. Four fields were compared which were not fertilised for 2, 6, 19 or 45 years, while hay making continued. This was done to restore former species-rich grassland communities. We tested the hypothesis that the increase in species diversity in these grasslands was attended by an increase in the number of limiting nutrients.We observed clear shifts in the type and extent of nutrient limitation. Fields which were recently fertilised were characterised by nitrogen and potassium limitation, while phosphorus limitation increased in importance towards the later stages of succession. In the last field (45 years unfertilised) N, P and K equally limited production at the community level. These conclusions differed from those drawn from a fertiliser trial in these same four fields, which failed to detect phosphorus limitation.It is concluded that the use of this method provides a valuable extra source of information while studying relationships between nutrient limitation and species diversity in grassland communities.     

Phycoremediation: key issues for cost-effective nutrient removal processes

Phycoremediation applied to the removal of nutrients from animal wastewater and other high organic content wastewater is a field with a great potential and demand considering that surface and underground water bodies in several regions of the world are suffering of eutrophication. However, the development of more efficient nutrient removal algal systems requires further research in key areas. Algae growth rate controls directly and indirectly the nitrogen and phosphorus removal efficiency. Thus, maximum algae productivity is required for effective nutrient removal and must be considered as a key area of research. Likewise, low harvesting costs are also required for a cost-effective nutrient removal system. The use of filamentous microalgae with a high autoflocculation capacity and the use of immobilized cells have been investigated in this respect. Another key area of research is the use of algae strains with special attributes such as tolerance to extreme temperature, chemical composition with predominance of high added value products, a quick sedimentation behavior, or a capacity for growing mixotrophically. Finally, to combine most of the achievements from key areas and to design integrated recycling systems (IRS) should be an ultimate and rewarding goal.     

Size-related auto-fragment production and carbohydrate storage in auto-fragment of <Emphasis Type="Italic">Myriophyllum spicatum</Emphasis> L. in response to sediment nutrient and plant density

Size-related asexual reproduction of submersed macrophytes is still poorly understood. Here, we investigate how size-related auto-fragmentation in Myriophyllum spicatum L. responds to sediment nutrients and plant density. An experiment was carried out with sediments containing two different nutrient levels and with two levels of plant density. The results show that sediment nutrients and plant density brought about a strong dependency of auto-fragment production and the amount of total non-structural carbohydrate (TNC) storage in auto-fragments on individual plant size (total plant biomass). However, these two factors acted differently on size dependency. Sediment nutrients positively affected auto-fragment production and the amount of TNC in auto-fragments of M. spicatum. High concentrations of sediment nutrients significantly increased these two traits in absolute value and the value relative to plant size. Although the auto-fragment biomass and the amount of TNC in auto-fragments did not differ between density treatments when plant size was considered, the absolute values of these two traits were much larger in the low plant density treatment than in the high plant density treatment, which suggested an indirect negative effect of plant density on the auto-fragmentation of M. spicatum. In addition, higher percentages of large auto-fragments (>100 mg) were produced by plants that grew in nutrient poor sediment and low plant density environment than plants in nutrient rich sediment and high plant density environment. These results do not solely highlight a size-dependent effect, but also a size-independent effect of auto-fragment production and the amount of TNC in auto-fragments of M. spicatum. Furthermore, such size-independent effects can be explained by the significant biomass partitioning differences and the similar TNC-concentrations in auto-fragments under different environmental conditions.     

Allelopathy as a Tool in the Management of Biotic Resources in Agroecosystems

In modern agriculture, natural plant communities may be replaced by a single crop species. Weeds, some microorganisms, and viruses, as well as some herbivores are organisms that should be eliminated. Pesticides and fertilizers not only affect the pests and crops, but soil, non-pest species, water, food, and humans. In traditional agriculture weeds are components with an important ecological role in the maintenance of the system. Some weeds have been used as tools to control the growth of other weeds in traditional agroecosystems. Researchers on sustainable and organic agriculture get valuable information from traditional agriculture and currently are conducting research on plant breeding, soil fertility and tillage, crop protection, and cropping systems. Allelopathy and chemical ecology are directly involved in each of these fields and can play an important role in crop productivity, conservation of genetic diversity, and maintenance of ecosystems stability. Allelopathy has been shown to be related with problems of chemical interference between crops and weeds, crops and crops, toxicity of crops and weeds residues, and/or crops and weeds exudates. Problems of autotoxicity, orchard replanting, and forest regeneration are also referred as allelopathic. Allelopathy is strongly coupled with other stresses of the environment, including insects and disease, temperature extremes, nutrient and moisture variables, radiation, and herbicides. These stress conditions often enhance allelochemical production and increase the potential for allelopathic interference. Allelopathy offers potential for weed control through the production and release of allelochemicals from plants. Allelochemicals may impact the availability of nutrients through effects on the symbiotic microbes. Destruction and changes in the use of soils in the tropics have decreased biodiversity, bringing about the loss of valuable natural products. Many different types of useful products such as natural pesticides and drugs can arise from allelopathy studies. New methods must be generated for allelopathy as a part of the biotic resources management strategies.     

Low ratios of silica to dissolved nitrogen supplied to rivers arise from agriculture not reservoirs

Coastal marine systems are greatly altered by toxic marine algae, eutrophication and hypoxia. These problems have been linked to decreased ratios of dissolved silica to inorganic nitrogen (Si : DIN) delivered from land. Two mechanisms for this decline under consideration are enhanced nitrogen (N) fertiliser losses from agricultural lands or Si sequestration in reservoirs. Here we examine these mechanisms via nutrient concentrations in impoundments receiving water from 130 watersheds in a landscape representative of the agriculture that often dominates coastal nutrient inputs. Decreased Si : DIN was correlated with agriculture, not impoundment. Watersheds with > 60% agricultural land yielded highest DIN, whereas Si was uncorrelated with agricultural intensity. Furthermore, eutrophic lakes were dominated by Cyanobacteria that use little Si, so reservoirs did not diminish Si : DIN. Instead, Si : DIN increased slightly as reservoir residence time increased. These data suggest that impoundments in agricultural watersheds may enhance the water quality of coastal ecosystems, whereas fertiliser losses are detrimental.