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The evolution of environmental policy is increasingly driven by the emergence and interaction of policy concepts and the frameworks, knowledge, and ideas they employ. We argue that policy actors' creative use of policy concepts often leads to their combinatorial development. In this policy process, the concepts interact and shape each other's policy relevance and future development under the influence of ideas, knowledge, and political factors. We formulate this new research approach using ideational and policy process theories. In particular, we explicate internal and contextual combinatory elements that enable policy change resulting from mutual development of policy concepts. For an empirical demonstration, we analyze the conceptual innovation, rise, and ramifications of nutrient recycling as a new segment of Finnish environmental policy. [ABSTRACT FROM AUTHOR]

Aquaculture has grown rapidly to play a crucial economic and social role and meet the increasing global demand for seafood. As aquaculture intensifies, there is increasing pressure to find more sustainable practices that save resources and reduce waste. Major wastes and by-products from aquaculture were quantified across a full range of farming types. Key opportunities for wastewater treatment and by-product recovery include nutrient recycling through a combination of biofilters, bioaccumulation and multitrophic systems. To support a sustainable intensification of aquaculture, improvements in by-product harvesting, accumulation and processing methods require further investigation. Likewise, energy generated from by-products can potentially support intensified production through land-based recirculating aquaculture systems (RAS). Future challenges faced by the reuse of side streams include control of food safety and gaining consumer acceptance. Combined with increases in resource use efficiency across the aquaculture sector, from feeding methodologies to product storage, nutrient recycling can enable aquaculture to contribute sustainably toward the nutritional requirements of billions of people over the next century. [ABSTRACT FROM AUTHOR]

Residue management is one of the most difficult tasks in the modern-mechanized agriculture with the intensification of cropping systems, which leads to reduced sowing window between two crops and farmers prefer in-situ burning of crop residues. Therefore, the present study was conducted to assess the effect of zero tillage (ZT) based residue management on soil health parameters in maize (Zea mays L.)–chickpea (Cicer arietinum L.) rotation in black soils of central India. After 4 years of study, the soil bulk density was reduced by 3.0–10.2% and volumetric moisture content was improved by 10.2–19.3% at 0–10 cm soil depth in ZT with residue over conventional tillage (CT). The soil organic carbon and labile carbon were increased by 13.6–61.7% and 6.0–22.0%, respectively, at 0–10 cm soil depths. Similarly, ZT with residue increased the KMnO4-N, Olsen-P and NH4OAc-K, and total fungal and actinomycetes density in surface soil as compared to CT. Thus, our study advocates that ZT with residue retention (1.8–5.4 Mg ha–1 maize and 0.8–2.4 Mg ha–1 chickpea residue) should be implemented for sustainable soil health in Vertisols (Typic Haplustert) of central India and other similar agro-ecological systems. [ABSTRACT FROM AUTHOR]

Wastewater reuse from fertirrigation has become a new strategy for sustainable crop production, especially because there is a need to save fresh water. It can also reduce fertilizer costs and environmental pollution. This work aimed to evaluate the production of tomato and eggplant seedlings irrigated with wastewater reuse from fertirrigation. The experiment was carried out in a completely randomized design in a 2 × 4 factorial scheme with four replicates, where each replicate was represented by 25 seedlings. Treatments were represented by two crops (tomato and eggplant) and four concentrations of fertirrigation wastewater leachate (Treatment 1 (T1): 25%; Treatment 2 (T2): 50%; Treatment 3 (T3): 75% and Treatment 4 (T4): 100%). Seedlings were evaluated for the following parameters: number of leaves, seedling height, basal stem diameter, leaf area, total dry mass, and relative water content. With the exception of the basal stem diameter, eggplant seedlings were affected by leachate concentrations for all the other parameters evaluated, while tomato seedlings presented significant responses for all variables. It was observed that the use of concentrations between 50 and 75% of fertirrigation wastewater leachate can be a possible alternative to reduce the use of chemical fertilizers in the production of tomato and eggplant seedlings. [ABSTRACT FROM AUTHOR]

Integrating a combination of organic matter management (OMM) practices can increase soil fertility, biomass, and nutrient recycling, but evidence of this potential is limited. This study tested the impact of integrating a combination of OMM practices on soil fertility, biomass, and nutrient recycling on smallholder farms. Following a randomised complete block design, a four-season experiment was conducted in 2018-2019 on 10 farms. The treatments (T) included T1: cowpea-maize-bean-maize rotation; T2: cowpea-maize-bean-maize rotation + farmyard manure; T3: Faidherbia albida alleys + cowpea-maize-bean-maize rotation; T4: F. albida alleys + cowpea-maize-bean-maize rotation + farmyard manure; and T5 (control): maize monocrop with diammonium phosphate application at 50 kg/ha application rate. T1-T4 are the OMM practices. The maize in T2-T4 was undersown with Mucuna pruriens. Soil fertility parameters (i.e. pH, water holding capacity, nitrogen, phosphorus, and potassium), biomass, and nutrients in the biomass were determined. There were no differences in soil fertility parameters among all treatments (P > 0.05). From the second to the fourth season, biomass was consistently higher under T3 and T4 than in other treatments. Moreover, the nutrients in biomass were higher in T3 and T4 than in other treatments, an indicator that OMM practices with alley crops can increase nutrient recycling. [ABSTRACT FROM AUTHOR]

The circular economy (CE) is currently generating considerable expectations. The concept describes an aspired future but does not provide clear guidance for policy-making. As policy outcomes often rest on initiatives generated in a bottom-up fashion, our attention must be directed to the ways policies are made accessible and interesting to those who might take the initiative. We claim that on-line publicity plays a key role in this. Our findings from a hyperlink analysis focusing on a government funding call for nutrient recycling in Finland show how multiple versions of the policy topic unfold online, as emergent hyperlink clusters prioritize specific agents, material circuits, and policy visions over others. The topic becomes connected with activities and agendas to create path dependencies and to strengthen existing divisions rather than to advocate change. Thus, we argue that CE policy design must recognize the way policy is shaped through online publicity creation. [ABSTRACT FROM AUTHOR]

A completely randomized factorial experiment was conducted to evaluate the growth and biomass production of single- and mixed crop species inoculated with mycorrhizae. Radish, (R), safflower (SF), pearl-millet (PM), mustard (M), field peas ((FP), faba-bean (FB), common vetch (CV), and berseem clover (BC) and their blends as R-SF-PM-M, FP-FB-CV-BC, R-SF-PM-M-FP-FB-CV-BC, R-SF-M-FP-FB-CV-BC, and PM-FP-FB-CV-BC were planted in a pot culture. The mycorrhizal inoculum significantly influenced the cover crops growth and biomass production under sterilized soils than that of non-sterile soils. While the safflower produced the highest total biomass, the pearl millet and field peas produced the lowest total biomass. Generally, in sterile and mycorrhizal conditions plant grown better and have high total C fixation. Within non-sterile and mycorrhizal inoculation, Safflower (1383.1 g C m−2) and Berseem Clover (1235.5 g C m−2) as a single species have fixed highest amount of carbon as biomass. Mycorrhizae inoculated BC+CV+FB+FP+SF+PM blends had a return of 1365.0 g C m−2 in non-sterile soil. Our results suggested that cover crops in single or mixed stands with mycorrhizal inoculations are expected to provide a significantly greater amount of biomass, which would contribute to soil organic matter and nutrient recycling for crop production. [ABSTRACT FROM AUTHOR]

The successful sustainable production of high-quality and high-yielding tomatoes, particularly, by deploying precision agriculture with less water, nutrient, and energy consumption in a controlled environment has important roles in supporting plant and ecosystem sustainability, human nutrition and diet, and economic development worldwide. Among such methods, aquaponics provides more advantages than conventional and hydroponic cultivations by reusing the wastewater and, thereby, improving energy, water and nutrient use efficiency, financial gain, as well as plant and ecosystem sustainability. However, it requires more biological and technical knowledge to maintain the system's balance and optimal condition. The proper management of the greenhouse climate and the controlled environmental system, agricultural practices, inputs, and nutrients recycling are the foremost determinant factors of effectiveness, cost-efficiency, productivity, as well as plant and ecosystem sustainability. The knowledge of optimal growth and recycling conditions in aquaponics is still developing. Due to the differences of the materials and methods of the related studies and various types, combinations, and contents of growth media substrates and fertilizers, genetic diversities and differential responses, optimal growth conditions and interactive effects of the (micro)organisms, a deep understanding of the influence of the mentioned factors are required to reach the optimum results. Therefore, the most efficient tomato culture practices in aquaponics and most importantly in the vermi-ponic unit are discussed in this paper to provide insight into developing the most successful cost-effective sustainable systems for tomato production. [ABSTRACT FROM AUTHOR]

Six 1.2-m3 tanks were stocked with an initial biomass of 500 g m-3 of Litopenaeus vannamei juveniles (individual weight: 1.0±0.3 g), to evaluate the effect of biofloc promotion on water quality and on shrimp growth and production, and to identify the dominant taxa in the heterotrophic communities present in experimental closed cultures. Feeding was ad libitum twice daily with 35% protein shrimp feed. Three tanks were managed as biofloc technology (BFT) systems, adding daily an amount of cornmeal equivalent to 50% of the shrimp feed supplied. The remaining three received only shrimp feed and served as controls. Experiment lasted 21 days. The mean concentrations of P-PO43- and inorganic dissolved N species (TAN, N-NO2-, N-NO3-) were significantly lower (P<0.5) in BFT than in the control. The individual final weight, increase in biomass, food, and protein conversion rates were significantly better in BFT than in the control (P<0.05). The mean N content of the shrimp biomass gained in the BFT cultures was equivalent to 45.7% of the protein-N added as feed, and was significantly higher than the 34.7% recycled into shrimp biomass in the control cultures. Bacterial concentrations were not significantly different. Vibrionaceae dominated in both systems; in both some isolates were potential pathogens, and diversity was higher in the control than in the BFT treatment. The advantages of BFT technology are confirmed by the significantly lower TAN and N-NO2- concentrations, as well as by the better shrimp performance in terms of growth, biomass yield, and food and protein conversion efficiency. [ABSTRACT FROM AUTHOR]

The intensive breeding of beef cattle in Juncosa de les Garrigues (Catalonia, Spain) leads to the production of a large volume of manure that needs appropriate management. Land application in the area at agronomic rates is not enough to ensure good management practices, making necessary extended on-farm storage and the export of part of the production to long distances. In this context, the implementation of a collective treatment based on composting could help in enhancing the handling of manure. We assessed a full-scale composting process based on turned windrows (W), and involving treatment of beef cattle manure (CM) alone (two typologies were considered according to carbon-to-nitrogen ratios of ~25 (CM1, W1) and ~14 (CM2, W2)), or mixed with bulking agent (CM2/BA, W3) and dewatered digested sewage sludge (CM2/BA/DDSS, W4). Composting significantly improved the transportability of nutrients (final volumes were 40–54% of the initial volume). Temperature >55°C was reached in all the treatments but following different time patterns. Under the applied conditions of turning and rewetting, 14 weeks of processing did not ensure the production of stable, and mature, compost. Thus, only compost from W1 attained the maximum degree of stability as well as concentration of ammonium–N < 0.01% (with ammonium–N/nitrate–N ratio of 0.2) and low phytotoxicity. However, high pH, salinity, and heavy metal contents (Cu and Zn) may limit its final use. Addition of BA was advised to be kept to minimum, whereas use of DDSS as a co-substrate was not recommended in agreement to the higher loss of N and levels of heavy metals in the final compost. [ABSTRACT FROM AUTHOR]

A field experiment was conducted for 3 years during 2006–2009 in India to study the effects of plant nutrient recycling through crop residue management, green manuring, and fertility levels on yield attributes, crop productivity, nutrient uptake, and biofertility indicators of soil health in a rice–wheat cropping system. The study revealed that soil microbial biomass carbon (SMBC) and carbon dioxide (CO2) evolution were significantly greatest under crop residue incorporation (CRI) + Sesbania green manuring (SGM) treatment and were found at levels of 364μg g−1soil and 1.75μg g−1soil h−1, respectively; these were increased significantly by recycling of organic residues. Activities of dehydrogenase and phosphatase enzymes increased significantly after 3 years, with maximum activity under CRI + SGM treatment. The CRI with or without SGM significantly influenced the plant height, number of tillers m−2, number of grains panicle−1or ear−1, and 1000-grain weight. Mean yield data of rice and wheat revealed that CRI or crop residue burning (CRB) resulted in slightly greater yield over crop residue removal (CRR) treatment. The CRI + SGM treatment again observed significantly greatest grain yields of 7.54 and 5.84 t ha−1and straw yields of 8.42 and 6.36 t ha−1in rice and wheat, respectively, over other crop residue management treatments. Total nitrogen (N), phosphorus (P) and potassium (K) uptake in rice–wheat system was greatest with amounts of 206.7, 37.2, and 205.6 kg ha−1, respectively, in CRI + SGM treatment. Fertility levels significantly influenced the rice and wheat yield with greatest grain yields of 6.66 and 5.68 t ha−1and straw yields of 7.94 and 5.89 t ha−1in rice and wheat, respectively, with the application of 150% of recommended NPK. Total NPK uptake in rice–wheat system also increased significantly with increase in fertility levels with greatest magnitude by supplying 150% of recommended NPK. Overall, nutrient recycling through incorporation of crop residues and Sesbania green manuring along with inorganics greatly improved the crop productivity, nutrient uptake, and biofertility indicators of soil health with substantial influence on SMBC, CO2evolution, and dehydrogenase and phosphatase enzyme activities. This indicates that crop residue management along with Sesbania green manuring practice could be a better option for nutrient recycling to sustain the crop productivity and soil health in intensive rice–wheat cropping system in India as well as in similar global agroecological situations, especially in China, Pakistan, and Bangladesh. [ABSTRACT FROM AUTHOR]

Effective wastewater treatment through conventional methods that rely on heavy aeration are expensive to install and operate. Duckweed is capable of recovering or extracting nutrients or pollutants and is an excellent candidate for bio-remediation of wastewaters. Such plants grow very fast, utilizing wastewater nutrients and also yield cost effective protein-rich biomass as a by-product. Duckweeds being tiny surface-floating plants are easy to harvest and have an appreciable amount of protein (15%–45% dry mass basis) and a lower fiber (7%–14% dry mass basis) content. Besides nutrient extraction, duckweeds has been found to reduce total suspended solids, biochemical oxygen demand (BOD), and chemical oxygen demand in wastewater significantly. Depending on the initial concentrations of nutrients, duckweed-covered systems can remove nitrate (NO3−) at daily rates of 120–590 mg NO3−m−2(73%–97% of initial concentration) and phosphate (PO4−) at 14–74 mg PO4−m−2(63%–99% of initial concentration). Removal efficiencies within 3 days of 96% and 99% have been reported for BOD and ammonia (NH3). Besides several genera of duckweeds (Spirodela,Lemna,Wolffia), other surface-floating aquatic plants like water hyacinth (Eichhornia) are well known for their phyto-remediation qualities. [ABSTRACT FROM PUBLISHER]

Litter fall and its decomposition rate play an important role in nutrient recycling, carbon budgeting and in sustaining soil productivity. Litter production and the decomposition rate were studied on commonly planted broad-leaved Eucalyptus (Eucalyptus globulus, Eucalyptus camaldulensis, Eucalyptus saligna) and coniferous (Juniperus procera, Cupressus lusitanica, Pinus patula) plantation species and compared with the adjacent broad-leaved natural forest. The production of litter was recorded by litter traps and the decomposition rate was studied by nylon net bag technique. Litter production under broad-leaved plantation species and natural forest (that varied from 9.7 to 12.6 Mg ha−1 y−1) was significantly higher (p<0.05) than that under coniferous species (that varied from 4.9 to 6.6 Mg ha−1 y−1). The average concentration of C and N in fresh mature leaves was higher than in leaf-litter fall, implying that both C and N were either sorbed in the plant system or lost through decomposition, leaching or erosion during the leaf-litter fall period. The amount of N, which potentially returned to the soil through the leaf-litter fall, tended to be higher in natural forest than in Eucalyptus plantations. The residual litter mass in the litter bag declined with time for all species. The annual dry matter decay constant (k) varied from 0.07 m−1 in Pinus patula to 0.12 m−1 in Eucalyptus saligna. The half-time (t0.5) decay varied from 6.0 for Eucalyptus saligna to 9.7 months for Pinus patula. The results suggest that the decomposition rate in Pinus patula was relatively lower than the other species and the litter production under broad-leaved Eucalyptus was comparatively higher than that in coniferous species. Overall the litter decomposition was fast for all species. The higher litter production and its relative faster rate of decomposition is a positive aspect to be considered during species selection for the restoration of degraded habitats given other judicious management practices such as prolonging the rotation period are adhered to. [ABSTRACT FROM PUBLISHER]

Wood ash treatment can probably increase forest productivity on low fertility sites. However, the resulting effect on the carbohydrate concentration as the main carbon and energy reserve in trees is little studied. In 2000, a square of 0.1 ha sandy soil below a 19-year-old Scots pine (Pinus sylvestris) plantation was treated with raw fly ash (0.5 kg·m-2); untreated square was used as control. One year after the treatment, carbohydrates (glucose, fructose, sucrose, maltodextrins, starch and excess bound fructose) were analyzed enzymatically from current-year and one-year-old needles. The ratio K/N in needles suggested an improved balance between these elements in treated trees, in which the K concentration was higher. The largest relative differences (50% of control) were observed in glucose and fructose in summer. The squares did not differ in the concentration of the accumulated carbohydrate reserves in needles during low temperature stress in winter and before the growth of new shoots in spring. During the vegetation period decreased levels of soluble carbohydrates and starch were observed (max 70% of the control value around 100 mg total carbohydrates g-1 dry mass). Because the experiment was designed without true replicates, reasons for the observed differences require further study. [ABSTRACT FROM AUTHOR]

It is widely documented that vertical flow constructed wetlands are efficient for producing well nitrified effluent. However, because the treated effluent is oxygen saturated and has a low availability of carbon, the removal of total nitrogen is limited. We hypothesize that by recycling the fully nitrified effluent to the pretreatment unit and the sedimentation tank (where conditions are favorable for denitrification) the removal of total nitrogen from the wastewater can be enhanced. In order to assess the effects of recycling volumes, we monitored the nitrogen removal in an experimental vertical flow constructed wetland, consisting of a 2 m³ sedimentation tank, two vertical flow beds of 10 and 5 m², and the necessary pumping equipment and controllers to manage the loading and recycling volumes. The system was loaded with approximately 0.5 m³ d&sup-1;, and the recycling volumes evaluated were equal to the loading rate (100% recycling), as well as twice (200%) and three times (300%) the loading. The system produced a fully nitrified effluent independent of recycling rate. However, recycling increased removal of total-N in the system from ca. 1% removal when there was no recycling to 52%, 66%, and 68% removal with 100, 200, and 300% recycling, respectively. The optimal recycling rate seems to be 100-200%. At lower recycling rates, the removal of total-N was poor, and at higher recycling rates, the system became hydraulically overloaded, compromising both the denitrification capacity of the sedimentation tank and the nitrification capacity of the vertical bed. [ABSTRACT FROM AUTHOR]

Benthic macrofaunal populations through their feeding, bioturbation, burrow construction and sediment irrigation activities have profound influences on organic matter inputs to marine sediments (biodeposition) and on the vertical distribution of deposited organic matter within the sediment. These effects in turn influence the rates and pathways of organic matter mineralisation, and element cycles. Similarly, bioturbation, burrow construction and burrow irrigation are major determinants of sediment-water column fluxes of oxygen and nutrients. In this review, I discuss the influences of the different benthic macrofaunal feeding (functional) groups on mineralisation processes and sediment-water column fluxes of particulate and dissolved nutrients. How these effects influence diagenic processes, the balance between aerobic and anaerobic processes, and the redox status of the surficial sediments. Finally, I discuss some of the limitations of the predominantly laboratory techniques which have been used to study "macrofaunal effects" and how this hinders the inclusion of the effects in quantitative sediment biogeochemical models. [ABSTRACT FROM AUTHOR]

A wastewater-fed, partly indoor aquaculture plant (36 basins, 360 m2 and 420 m3 in total) was designed in Otelfingen/Zurich, Switzerland. It was charged with the effluent from a methanization plant processing organic household waste and started operation in spring 1998. The aim of the successive arrangement of the different modules and steps was to efficiently recycle water-borne nutrients in the form of aquatic biomass products, such as floating (ornamental) macrophytes, fish, zoo- and phytoplankton, suitable for selling on the Swiss market. Besides treating the effluent (total organic carbon [TOC], total nitrogen, nitrate [NO3-N], ammonium [NH4-N], and total phosphorus concentrations being 670 g/m3, 255 g/m3, 150 g/m3, 95 g/m3, and 52 g/m3, respectively) according to Swiss law requirements, the research focused on the search for suitable aquatic organisms and their testing at different environmental conditions. During the 16-week experimental period, a total of 2,150 kg fresh weight (FW) of biomass (97% as floating macrophytes) was harvested. This way, 176 g/week nitrogen and 47 g/week phosphorus were eliminated by assimilation, corresponding to 25-35% of the system's inflow. Due to relatively high evapotranspiration rates (on average 35.4 mm/week) and for water reconditioning purpose in the fish stocking basins, fresh water was added. Nevertheless, the system's final effluent was very low (21% of total inflow plus rainfall) and was carrying only about 2% and 0.5% of the input loads of nitrogen and phosphorus, respectively. Hence, the elimination rate was significantly above the average performance of a conventional system normally applied in Middle Europe, although the concentration values of most parameters in the outflow were comparable. Macrophyte production (and thus nutrient assimilation) was close to theoretical maxima in basins with high nutrient levels. Both plankton and fish growth were, at their best, only moderately satisfying. The semi-continual planktonic microalgae culture, and therefore also zooplankton culture, could be improved if the light absorbing humic substances were removed in a pre-treatment. Under given conditions (i.e., temperate climate) fish would rather play an accompanying role in the ecological production process. A wastewater-fed aquaculture facility resembles an integrated production plant rather than a wastewater disposal site. In addition to that, it has potential to prove advantageous over the highly developed conventional wastewater treatment plants established in Middle Europe. Further research in this field is essential and also recommended, considering political programs like Agenda 21, which contemplate the need for sustainable strategies for handling resources. [ABSTRACT FROM PUBLISHER]