1,721,028 research outputs found
Aquaponics: smart system for food production in smart cities
Full text linkThis study aimed to test the rearing of common carp (Cyprinus carpio) at two stocking densities on water quality, fish growth and leaf vegetables (Cichorium intybus L. Catalogna group, Lactuca sativa L., and Beta vulgaris L.) yield in an aquaponic low-tech system compared to a hydroponic cultivation. Three treatments with three replications were studied: low fish density (AP1, 2.5 kg/m3), high fish density (AP2, 4.6 kg/m3) and hydroponic (HP). The trial lasted 133 days. The average daily evapotranspirated water from the systems was about 1.4% of the total (600 L). Fishes reached higher specific growth rates (0.79 vs. 0.68% d-1; P<0.001) and final body weights (516 vs. 413 g; P<0.05) in AP1 than AP2 treatment. However, the biomass production increased with increasing stocking density (4.45 kg/m3 vs. 6.88 kg/m3 for AP1 and AP2, respectively; P=0.01). On average, the highest total vegetables production was obtained in AP1 treatment (10.1 kg/m2) followed by HP (9.1 kg/m2) and AP2 (7.1 kg/m2) (P<0.05). The vegetables produced in aquaponic systems had a higher glucose content (+28.4%) than HP treatment, regardless of fish density. Water O2 content did not change among crop cycles in the HP treatment, while it decreased as fish load increased. The water NH4-N content was always below the thresholds for the reared fish. Our data show the fundamental importance of fish load in aquaponic systems suggesting that, in the proposed low-tech system, an initial fish density of 2.5 kg/m3 is suitable
Vegetation contribution on phosphorus removal in constructed wetlands
No full textConstructed wetlands have been proven as efficient natural-like technologies to treat different wastewater types. However, phosphorus (P) removal with these systems is still a challenge due to their low performance. This study aims to compare, in microcosm subsurface flow constructed wetland system, the PO4-P apparent balance of five macrophytes (Carex elata All., Juncus effusus L., Phalaris arundinacea L. var. picta, Phragmites australis (Cav.) Trin., and Typha latifolia L.) and an unvegetated control to evaluate plants' contribution in P removal. Compared with unvegetated systems, plant presence increased the PO4-P removal between 5.4% (P. arundinacea) and 9.4% (C. elata). Only T. latifolia was able to remove more than the PO4-P load (13.05 g m−2) whereas the removal reached 86.2%, 48.1%, 37.6% and 36.0% for P. aundinacea, C. elata, J. effusus and P. australis, respectively. Considering the total P load (51 g m−2), its removal from wastewater reached the highest value with T. latifolia (21.8% of inlet quantity) whereas the other species had an average removal value of 6.5%. The biennial study indicates: 1) T. latifolia as the best solution to remove PO4-P from the wastewater being able to remove more than PO4-P load (1.5 times); 2) P. aundinacea as other possible choice able to remove about 86% of PO4-P load
Maize yield and N dynamics after cover crops introduction
Full text linkThe use of cover crops (CCs) is widely suggested as a sustainable agricultural practice. Nevertheless, conflicting results have been reported about the short-term effect of CCs on cash crop yields and the soil nitrogen (N) dynamics. Within this framework, the present study aims to examine the short-term impact of CC introduction into a conventional agricultural system on silage maize yield and the N dynamics (maize N uptake, N use efficiency (NUE), soil nitrate content (Nmin), and apparent soil N mineralization and immobilization processes) in northern Italy. The CC systems (∼5.5 ha) included a fixed treatment (FI) with a gramineous species (triticale), a 2-year gramineous-legume species succession (SU) (rye, clover), and a weed-covered control treatment (NoCC). In the first year, triticale and rye had the same total (aboveground + root) final biomass (2.5 Mg ha−1 on average), C:N ratio (29), and N uptake (36.4 kg ha−1). However, triticale developed faster in the first winter months. Both grass species equally reduced the soil Nmin content over the winter season (as valid catch crops), but they caused apparent N immobilization during the following maize growing season. In the second year, clover produced the same total biomass as triticale did (1.8 Mg ha−1), but with a higher total N content (72.5 kg ha−1) and lower C:N ratio (27) which determined a lower apparent N immobilization. The introduction of CCs did not affect the yield of maize. During the maize growing season, lower N uptake and NUE were recorded after CCs grasses species cultivation compared to clover and NoCC. These observations suggest that a key aspect to be considered when dealing with CCs is understanding the N mineralization-immobilization processes related to CC residue decomposition, which might determine N availability for the subsequent crop and in turn its production quality (N uptake), even when the yield is not affected
Agronomic management strategies to increase soil organic carbon in the short-term: evidence from on-farm experimentation in the Veneto region
Full text linkBackground and aims: Organic fertilizers and cover crops (CC) are considered crucial strategies to pursue the objective of increasing soil organic carbon (SOC). The present research focuses on an ‘on farm experimentation’ to assess the combined effects of organic fertilization with different biomasses, CC and irrigation on SOC stock. Methods: A 4-year on-farm experimentation was co-developed with local farmers and a land reclamation authority in north-eastern Italy on a biennial maize-soybean rotation. We examined the effects of two organic fertilizers (compost or digestate), three CC treatments (a fixed cover crop species – x triticosecale; a succession of cover crop species – Sinapis alba and Lolium multiflorum; no CC) under rainfed and irrigated conditions on the SOC content and stock, and crops yields. Results: All these integrated practices – except when digestate was applied in the field in the absence of a CC under rainfed conditions – determined a significant increase of the SOC stock after 4 years, matching the goals set by the ‘4 per mille’ initiative. The highest SOC increase was observed under irrigated management and compost fertilization, regardless of the presence or absence of a CC (range: 9.3–10.3 Mg ha−1 in the first 0–40 cm of soil). Soybean grain yields were comparable with those obtained in farms of the same rural district under business as usual, but maize grain yields were lower. Conclusion: SOC accumulation is achievable in the short term with abundant applications of organic biomass, but the strategy might lead to economic loss such as lower maize productivity
Short-term climate change effects on maize phenological phases in Northeast Italy
No full textThis study evaluates the response of maize growing cycle length to meteorological variables at regional scale particularly, in the short-term period, considering global climate change. The experiment was carried out in Veneto Region (Northeast Italy) where maize phenological data collected by the regional network from 2005 to 2007 were combined with temperature data to analyse the relationship between BBCH stages and thermal sum. The effects of climatic changes in the near and medium term on maize phenology and on water requirements were also evaluated over a grid of climatic data obtained from different climatic models. The piecewise analysis gave the best fitting between BBCH and Growing Degree Days observed data characterized by two lines with different slopes with BBCH 70 (beginning of fruit develop-ment) as changing stage. The angular coefficient of the first line was 2.6 times than the second one (0.028) suggesting that the early stages of the growing cycle are more sensitive to air temperature. The simulation of maize phenology evolution highlights a modest variation at the 2020-time horizon, while an expected reduction of maize growing cycle of about 10 days has been estimated for 2030-time horizon. Long-term phenological observation are desirable to confirm our findings and to improve the strength of dataset
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