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Evaluation of the sustainability and environmental footprint of different agricultural production systems, such as organic and conventional systems, is an open scientific debate. Presently, several agri-environmental indicators have been proposed; however, their reliability and interpretation are still under discussion. The investigation of biological, chemical, and physical soil health variables has been advocated for understanding the sustainability of agricultural systems, even though they are not univocal indicators. In the present study, both biological (abundances of ammonia-oxidizing archaea, AOA; ammonia-oxidizing bacteria, AOB; and nosZ) and physicochemical (pH; soil organic carbon, SOC; total Kjeldahl nitrogen, TKN; available phosphorus, P; and texture) soil variables were investigated to compare two soils under organic (OS) and conventional (CS) management after 15 years. Among the physicochemical variables analyzed, TKN content was higher whereas P content and pH values were lower in the OS than in the CS. The SOC content was not affected by agricultural management. Biological indicators showed significant differences in the soil nitrogen cycle. After 15 years, the OS showed a higher potential for N2O emission reduction (higher nosZ) and NO3- losses in the environment (higher AOA) than the CS. Therefore, we conclude that biological (AOA and nosZ) and chemical (P, TKN, and pH) variables can be regarded as soil health indicators for comparing different agricultural management systems.

Agricultural management affects soil fertility through the frequency and type of agronomic practices such as mechanical operations, type and rate of fertilizers, crop rotations, and residue management. This study evaluated the evolution of soil chemical properties (pH; electrical conductivity; soil organic carbon, SOC; total Kjeldahl nitrogen, TKN; and available phosphorous, PO4-P) over time in two farming systems, organically and conventionally managed, after 5 and 14 years after the establishment of both systems, in northeastern Italy. SOC content remained stable in the conventional farming system, but slightly decreased in the organic farming system, despite inputs from organic amendments. In contrast, soil TKN remained consistently higher in the organic farming system. The PO4-P increased over time, in both farming systems. Moreover, we observed that an increase of 1% in soil clay content resulted in increases of 0.0534 and 0.0053 g kg–1 in SOC and TKN, respectively. In conclusion, our results indicate that organic management does not have an advantage over conventional management in terms of soil organic matter accumulation.

Aquaponics is not only a forward-looking technology but it has also been proposed as a tool for teaching natural sciences at all school levels, from primary school to university. Life cycle assessment (LCA) has become a widely accepted method of evaluating the environmental impact of products and services. In this context, the aims of this paper were:1) to create a low-price AP system for possible use as didactic tool using recovered material; 2) to evaluate the environmental impact of a micro AP model (1.5 m2) through LCA analysis; 3) to verify whether this micro AP model is representative of full-scale AP systems (>50 m2) in terms of water quality and water consumption. Both, the water quality and the average daily water consumption of our system were in line with data reported in literature for larger aquaponics. LCA shows that materials and energy flows linked to the system management practices and energy consumption principally contribute to environmental impacts. The cumulative annual energy demand of micro aquaponic system was 1040.5 kWh; assuming that this system was built for a class of 25 students, the energy consumption of the learning activity using the proposed micro aquaponic system would be 41.6 kWh student−1 year−1. The results showed that the micro aquaponic system reliably mimics a full-scale unit and that it is a teaching tool with a relatively low environmental impact.