The fate and transport of 34 veterinary pharmaceuticals (PhACs) is investigated in swine slurry and dairy cattle manure-amended agricultural soils, from an experimental field site, by using both analytical and modelled data. Potential differences on PhACs fate, attributed to the application of distinct swine slurry fractions (total, solid, and liquid), are herein assessed for the first time. Surface and deep soil layers, up to a depth of 120 cm, were analyzed at different periods after an annual fertilization event. Using input data representing typical agricultural soil conditions and the PhACs concentration measured in organic fertilizers the transport of these pollutants was modelled for a period of 10 years, including the monitored annual fertilization event. Fluoroquinolone, tetracycline and pleuromutilin antibiotics, together with anti-helmintics and analgesic and anti-inflammatories, were detected in manure-amended soils, at average concentrations ranging from 0.078 to 150 µg/kg dw in surface layers, with the highest levels found in the fields fertilized with the swine slurry solid fraction. Even though severe disagreements were observed between experimental and simulated PhACs concentrations along the soil column, both approaches pointed out that target compounds strongly adsorb onto surface layers, showing limited mobility along the soil profile. Thus, repeated manure and slurry fertilizations will contribute in building up persistent PhACs residues in the uppermost layers of the soil, while leaching will be a minor process governing their fate towards the subsurface. The ecotoxicological risks posed by the occurrence of PhACs in soils were estimated to be low for terrestrial organisms. Nevertheless the antibiotic enrofloxacin showed some potential to induce negative effects to crops.

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The agri-food sector has moved towards a more linear production economy, partly caused by worldwide food demand. One clear example is the intensification of livestock production, with consequent manure-management and feed-production challenges, the effects of which have led to large environmental problems. Currently, efforts are being made to move the agricultural sector towards closed-loop alternatives. To ensure high environmental performance of these alternatives, realistic quantification of environmental impacts is needed. Thus, using Life Cycle Assessment (LCA) tools, we analyzed the environmental profile of six closed-loop maize scenarios focusing on different combinations of mineral fertilizer, digested organic fertilizer (digestate) from a manure co-digestion biogas plant, and rotation with (or without) catch crops (CCs) as a strategy to prevent nitrate leaching to groundwater and as a co-substrate in the biogas plant.Results demonstrated that replacing a large portion of the mineral fertilizers with digestate could help offset much of the total potential impact of global warming (by 25-35 %), resource depletion (by 94-96%), photochemical ozone formation (by 17-22 %), ozone depletion (by 96-99%) or even avoid it entirely as in freshwater eutrophication. However, digestate production and application contributed greatly to acidification (51%) and particulate matter (51-52%) categories, with minor differences depending on the species of CC used. An optimal combination of both digestate and mineral fertilizers is recommended. The incorporation of CCs in a maize rotation can reduce freshwater eutrophication impacts but increase global warming potential. Conclusions were drawn suggesting better management strategies to decrease environmental impacts of maize production.

The efficient use by crops of nitrogen from manures is an agronomic and environmental issue, mainly in double-annual forage cropping systems linked to livestock production. A six-year trial was conducted for a biennial rotation of four forage crops: oat-sorghum (first year) and ryegrass-maize (second year) in a humid Mediterranean area. Ten fertilization treatments were introduced: a control (without N); two minerals equivalent to 250 kg N ha-1 yr-1 applied at sowing or as sidedressing; dairy cattle manure at a rate of 170, 250 and 500 kg N ha-1 yr-1 and four treatments where the two lowest manure rates were supplemented with 80 or 160 kg mineral N ha-1 yr-1. They were distributed according to a randomized block design with three blocks. The highest N mineral soil content was found in the summer of the third rotation, in plots where no manure was applied. The yearly incorporation of manure reduced, in successive cropping seasons, the amount of additional mineral N needed as sidedressing to achieve the highest yields. Besides, in the last two years, there was no need for mineral N application for the manure rate of 250 kg N ha-1 yr-1. This amount always covered the oat-sorghum N uptake. In the ryegrass-maize sequence uptakes were as high as 336 kg N ha-1 yr-1. In the medium term, the intermediate manure rate (250 kg N ha-1 yr-1) optimizes nutrient recycling within the farming system, and it should be considered in the analysis of thresholds for N of organic origin to be applied to systems with high N demand.

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