The mobility and distribution of metals in the environment is related not only to their concentration but also to their availability in the environment. Most chromium (Cr) exists in oxidation states ...ranging from 0 to VI in soils but the most stable and common forms are Cr(0), Cr(III), and Cr(VI) species. Chromium can have positive and negative effects on health, according to the dose, exposure time, and its oxidation state. The last is highly soluble; mobile; and toxic to humans, animals, and plants. On the contrary, Cr(III) has relatively low toxicity and mobility and it is one of the micronutrients needed by humans. In addition, Cr(III) can be absorbed on the surface of clay minerals in precipitates or complexes. Thus, the approaches converting Cr(VI) to Cr(III) in soils and waters have received considerable attention. The Cr(III) compounds are sparingly soluble in water and may be found in water bodies as soluble Cr(III) complexes, while the Cr(VI) compounds are readily soluble in water. Chromium is absorbed by plants through carriers of essential ions such as sulfate. Chromium uptake, accumulation, and translocation, depend on its speciation. Chromium shortage can cause cardiac problems, metabolic dysfunctions, and diabetes. Symptoms of Cr toxicity in plants comprise decrease of germination, reduction of growth, inhibition of enzymatic activities, impairment of photosynthesis and oxidative imbalances. This review provides an overview of the chemical characteristics of Cr, its behavior in the environment, the relationships with plants and aspects of the use of fertilizers.
Aquaponics (AP) is a semi-closed system of food production that combines aquaculture and hydroponics and represents a new agricultural system integrating producers and consumers. The aim of this ...study was to test the effect of stocking densities (APL, 2.5 kg m-3; APH, 4.6 kg m-3) on water quality, growth performance of the European Carp (Cyprinus carpio L.), and yield of leafy vegetables (catalogna, lettuce, and Swiss Chard) in a low-technology AP pilot system compared to a hydroponic cultivation. The AP daily consumption of water due to evapotranspiration was not different among treatments with an average value of 8.2 L d-1, equal to 1.37% of the total water content of the system. Dissolved oxygen was significantly (p < 0.05) different among treatments with the lowest median value recorded with the highest stocking density of fish (5.6 mg L-1) and the highest median value in the hydroponic control (8.7 mg L-1). Marketable yield of the vegetables was significantly different among treatments with the highest production in the hydroponic control for catalogna (1.2 kg m-2) and in the APL treatment for Swiss Chard (5.3 kg m-2). The yield of lettuce did not differ significantly between hydroponic control and APL system (4.0 kg m-2 on average). The lowest production of vegetables was obtained in the APH system. The final weight (515 g vs. 413 g for APL and APH, respectively), specific growth rate (0.79% d-1 vs. 0.68% d-1), and feed conversion (1.55 vs. 1.86) of European Carp decreased when stocking density increased, whereas total yield of biomass was higher in the APH system (4.45 kg m-3 vs. 6.88 kg m-3). A low mortality (3% on average) was observed in both AP treatments. Overall, the results showed that a low initial stocking density at 2.5 kg m-3 improved the production of European Carp and of leafy vegetables by maintaining a better water quality in the tested AP system.
In the Mediterranean arid and semi-arid regions, large amounts of low quality waters could be used for crop irrigation, but the adoption of articulated classifications with too rigid quality limits ...can often reduce the recoverable quantities of water and make the monitoring of water quality too much expensive. Therefore, an evaluation of irrigation water quality based on only a few crucial parameters, which consider the crop species to be irrigated and the type of irrigation system and management adopted, can be an easy and flexible method for maximizing the reuse of wastewater and low-quality water for agricultural purposes. In this view, an irrigation water quality tool (IWQT) was developed to support farmers of arid and semi-arid regions on evaluating the use of low quality water for crop irrigation. The most significant and cheapest parameters of irrigation water quality were identified and clustered in three quality classes according to their effects on crop yield and soil fertility (agronomic quality indicators), human health (hygiene and health quality indicators), and irrigation systems (management quality indicators). According to IWQT parameters, a tool reporting a series of recommendations, including water treatment types, was implemented to guide farmers on the use of low quality irrigation water.
Aquaponics, the integrated multi-trophic fish and plants production in quasi-closed recirculating system, is one of the newest sustainable food production systems. The hydroponic component of the AP ...directly influences water quality (in turn influencing fish growth and health), and water consumption (through evapotranspiration) of the entire system. In order to assess the role of the design and the management of the hydroponic component on the overall performance, and water consumption of the aquaponics, 122 papers published from 1979 to 2017 were reviewed. Although no unequivocal results were found, the nutrient film technique appears in several aspects less efficient than medium-based or floating raft hydroponics. The best system performance in terms of fish and plant growth, and the highest nutrient removal from water was achieved at water flow between 0.8 L min-1 and 8.0 L min-1. Data on water consumption of aquaponics are scarce, and no correlation between the ratio of hydroponic unit surface/fish tank volume and the system water loss was found. However, daily water loss was positively correlated with the hydroponic surface/fish tank volume ratio if the same experimental conditions and/or systems were compared. The plant species grown in hydroponics influenced the daily water loss in aquaponics, whereas no effect was exerted by the water flow (reciprocating flood/drain cycle or constant flow) or type (medium-based, floating or nutrient film technique) of hydroponics.
► Different macrophytes treated well a reconstructed agricultural wastewater. ► Macrophytes had different nitrogen removal efficiency and allocation. ► Macrophytes choice and management is important ...in constructed wetland.
Five macrophyte species, Carex elata All., (Cae), Juncus effusus L. (Jue), Typhoides arundinacea (L.) Moench (syn. Phalaris arundinacea L.) (Pha) var. picta, Phragmites australis (Cav.) Trin. (Phr), and Typha latifolia L. (Ty), have been grown in mesocosms fed with a synthetic wastewater to acquire information on nitrogen balance and assess their capacity to abate nitrogen. The experiment, conducted during the growing seasons 2008–09 with four replicates, also included an unvegetated control. The mesocosms, filled with gravel, were fed with a solution of 105ppm of NO3–N and 100ppm of NH4–N in 2008 for a cumulative nitrogen load of 86g/m2 and with increased concentration in 2009 from 104ppm of NO3–N and 119ppm NH4–N, to 200ppm of NO3–N and 207ppm of NH4–N for a cumulative nitrogen load of 222g/m2. At the end of the experiment plants were harvested and N content in the above and belowground biomass was determined along with the amount of N contained in the roots and gravel microbial communities.
In the first growing season (8 months) Ty removed 82g/m2 (96% of the cumulative load) of TOT N, followed by Cae (94%), Jue (82%), Pha (81%), Phr (77%) and the control (48%). In the second growing season (6 months) all the vegetated treatments, except Jue, increased their efficiency, with Pha removing 216g/m2 (98% of the cumulative load) of TOT N, followed by Phr and Ty (97%), Cae (93%), Jue (75%) and the control (63%). Jue showed lower tolerance than the other species to high N concentration. Depending on the species, plants absorbed 53–75% of the two-seasons load and allocated 51–83% of this amount in the aerial tissues, showing the benefit of harvesting to remove N from the treatment site, at least in the medium short term. Application of the N balance allowed the gaseous losses to be estimated, giving values ranging from 51g/m2 in Ty to 114g/m2 in Pha, 17% and 37% of the total load respectively. If the target is the definitive elimination of the maximum amount of N from the treatment site, the sum of nitrogen harvested in the aerial part and the gaseous losses has to be considered. This value was maximum with Cae, with 227g/m2 over the two years.
Floating treatment wetlands (FTWs) represent a novel ecotechnology for the treatment of different types of wastewaters in natural or artificial water bodies, through the use of traditional rooted ...emergent macrophyte species supported by floating rafts. Although many studies have reported the treatment performances of FTWs, showing an excellent aptitude for removing nutrients, heavy metals as well as suspended solids, the investigation of vegetation has not received much attention up to now, especially for herbaceous ornamental plant species that could form an interesting opportunity to improve water quality and the esthetic-ornamental value of urban water bodies. For this reason, a pilot scale FTW was installed in Northern Italy to assess the growth performances of eleven wetland species having ornamental features: Canna indica L., Pontederia cordata L., Thalia dealbata Fraser ex Roscoe, Acorus calamus L., Juncus effusus L., Iris laevigata L., Mentha aquatica L., Oenanthe javanica (Blume) DC., Caltha palustris L., Sparganium erectum L. and Zantedeschia aetiopica (L.) Srengel. For these species, a suitability index was elaborated that considers plant survivability, above-mat biomass production, nitrogen uptake, root length and root-shoot ratio. On this basis, the results obtained clearly indicated that C. indica, P. cordata and T. dealbata were the most suitable species for FTW due to their high vigor and colonization of the floating mats (1638.9 g m–2, 483.4 g m–2, 566.1 g m–2 of above-mat dry biomass, respectively; 38.8 cm, 62.0 cm, 43.8 cm root length, respectively; 0.8, 0.9, 1.2 root-shoot ratio, respectively), survival (100%), nitrogen uptake (15.1 g m–2, 15.0 g m–2, 15.7 g m–2 respectively). On the contrary, A. calamus, S. erectum and Z. aetiopica did not present adequate features for use in FTWs.
Cover crops (CCs) can affect the cropping systems’ N dynamics and soil water content (SWC), but optimizing their potential effects requires knowledge of their growth pattern, N accumulation, and ...mineralization. For this purpose, a 3-year field experiment was initiated in northeast Italy involving a maize-soybean rotation. The objectives of this study were to (i) evaluate the use of time series vegetation indices (VIs) obtained from the Sentinel-2 satellite for monitoring the growth of CCs and estimating their biomass and N uptake at termination; (ii) investigate the effects of different CCs on cash crop yield and SWC; and (iii) use the simulation model CC-NCALC to predict the nitrogen contribution of CCs to subsequent cash crops. Three CC systems were tested: a fixed treatment with triticale; a 3-year succession of rye, crimson clover, and mustard; and a control with no CCs. Satellite imagery revealed that rye and triticale grew faster during the winter season than clover but slower compared to mustard, which suffered a frost winterkilling. Both grasses and mustard produced greater biomass at termination compared to clover, but none of the CC species affected SWC or yield and N uptake of the cash crop. A net N mineralization of all the CC residues was estimated by the model (except for the N immobilization after triticale roots residues). During the subsequent cash crop season, the estimated clover and mustard N released was around 33%, and the triticale around 3% of their total N uptake, with a release peak 2 months after their termination. The use of remote sensing imagery and a prediction model of CC residue decomposition showed potential to be used as instruments for optimizing the CCs utilization and enhancing cropping water and N fertilization management efficiency; however, it must be further analyzed with other CCs species, environmental conditions, and cropping systems.
► Median abatements were: 79% for COD, 64% for TN, 63% for NH4–N, and 61% for TP. ► For COD, the HF unit was more efficient than VF in reducing concentration. ► For TN and TP, VF and HF gave similar ...abatements. ► Average daily mass removal rates for COD was 31.4g/m2, for TN 17.5g/m2.
A full-scale hybrid constructed wetland (HCW) designed to treat 5m3/d of piggery wastewaters built in 2008 on a private pig farm in northern Italy was monitored from May to December 2009 to determine its efficiency in treating COD, total nitrogen (TN), ammonia nitrogen (NH4–N), nitrate nitrogen (NO3–N) and total phosphorus (TP). In situ measurements were also taken of pH, electrical conductivity (EC), dissolved oxygen (DO) and temperature (T). The system was composed of three vertical-subsurface flow wetlands (VF) (10m2 each, one planted with Canna indica and the other two with Symphytum officinale) working in parallel, followed by one horizontal-subsurface flow wetland (HF) connected in series (100m2 planted with Phragmites australis). The system was fed with pre-treated piggery wastewater with the total daily load (5m3) divided in two batches 11h apart. Wastewater samples were collected at the inflow (IN), outflow of VF unit (OUT-VF) and outflow HF unit (OUT-HF). Median COD concentration decreased from 1126 at the inlet to 235mg/L at the outlet (79% abatement). TN concentration was abated by 64% (671–240mg/L). NH4–N and NO3–N median inflow concentrations (390 and 6.61mg/L) were reduced by 63% and 53%, respectively, with median outflow concentrations of 145 and 3.14mg/L. Inflow phosphorus concentration of 23mg/L was abated by 61%. Average daily mass removal rates were 31.4g/m2 for COD, 17.5g/m2 for TN and 0.54g/m2 for TP.
The HF unit was more efficient than VF in reducing COD concentration; VF and HF gave similar abatements for TN and TP, but VF occupied a quarter of the surface of the HF.
The results show that the HCW is an effective solution for treating the excess pollutants deriving from animal wastewaters where sufficient land is not available for spreading.
Constructed wetlands (CWs) represent a green technology for digestate liquid fraction (DLF) treatment. However, previous research has warned about their performance when treating wastewater with high ...suspended solid and organic loads. In addition, the high NH4-N concentration typical of this wastewater can compromise vegetation establishment and activity. In view of this, a digestate pretreatment is needed. This study aimed to test the performance of filters filled with recovery materials, such as brick and refractory material, for DLF pretreatment. The effect on DLF physical (electrical conductivity, pH, dissolved oxygen, and temperature) and chemical (total nitrogen, ammonia–nitrogen, nitrate–nitrogen, total phosphorus, soluble phosphorus, and chemical oxygen demand) characteristics was monitored during eight weekly cycles. The effect of filtration on total nitrogen and ammonia–nitrogen removal began after about one month of loading, suggesting that an activation period is necessary for bacteria. For effective N removal, the presence of multiple digestate recirculations per day through the filters appears mandatory to guarantee the alternation of nitrification and denitrification conditions. For P removal, filling material particle size appeared to be more important than its composition. Unclear performances were observed considering chemical oxygen demand. Further studies on filling media and microbial community interactions, and the long-term efficiency of filters, are desirable.
The current agricultural system faces several challenges, the most important being the ability to feed the increasing world population and mitigate climate change. In this context, the improvement of ...fertilizers’ agronomic efficiency while reducing their cost and environmental impact is one of the biggest tasks. Available literature shows that many efforts have been made to develop innovative fertilizers defined as ‘smart fertilizers’, for which, different interpretations and definitions have been used. This paper aims to define, classify, and describe the new frontier of the so-called smart fertilizers with a particular focus on field-scale studies on herbaceous species. Most of the analysed papers associate the ‘smart’ concept to the controlled and/or slow release of nutrients, using both terms as synonymous. Some others broadened the concept, including the controlled release of nutrients to reduce the environmental impact. Based on our critical analysis of the available literature, we conclude that a fertilizer can be considered ‘smart’ when applied to the soil, it allows control over the rate, timing, and duration of nutrients release. Our new definition is: ‘Smart fertilizer is any single or composed (sub)nanomaterial, multi-component, and/or bioformulation containing one or more nutrients that, through physical, chemical, and/or biological processes, can adapt the timing of nutrient release to the plant nutrient demand, enhancing the agronomic yields and reducing the environmental impact at sustainable costs when compared to conventional fertilizers’. Highlights - A smart fertilizer allows to control the rate, timing and duration of nutrients release. - Nanofertilizers are powder or liquid formulations which involve the synthesis, design and use of materials at the nanoscale level. - Composite fertilizers are formulations containing nutrients mixed or coated with one or more materials that exploit synergy among materials. - Bioformulations are fertilizers containing active or dormant microorganisms capable to trigger physiological growth responses in plants. - Limited information is available for smart fertilizers on herbaceous crops in open field conditions.
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