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The extent to which different agricultural strategies may affect the uptake of potentially toxic elements (PTEs) by cropped plants is not entirely understood at a field scale. This study addresses the effect of seasonality, Trichoderma inoculation alone, or combined with different applications of commercial-grade clinoptilolite (i.e., foliar action, fertigation, and pellet) on the PTE content of early- and late-ripening cultivars of Cucumis melo L. Two similar field experiments were performed in spring and summer. For each cultivar/treatment combination, the input of PTEs [namely, chromium (Cr), copper (Cu), and lead (Pb)] into the soil-crop system through irrigation water, fertilizers, pesticides, and treatment products (i.e., Trichoderma and clinoptilolite products), as well as the PTE content of melon stem, leaves, and fruit, were measured through inductively coupled plasma-optic emission spectrometry (ICP-OES). Neither Trichoderma alone nor with clinoptilolite had a visible effect on PTE uptake by plants, whereas early season cultivation was strongly associated with reduced uptake of Cu and Pb. The high correlation of Cu and Pb content with stem and leaf calcium (Ca) content (used as a proxy for different transpiration rates under different growing seasons) indicated a possible uptake of these metals through Ca nonselective cation channels as a defense against drought stress. Reduced Cu and Pb concentrations were found in early-ripening fruit cultivated in spring. Concerning Cu and Pb risk management, in case of significant contamination in Mediterranean calcareous soils, early-ripening Cucumis melo L. cultivars are suggested instead of late-ripening ones.

Agriculture can play a primary role in the context of nutrients recovery by promoting the use of organic fertilizers (OFs). In order to use them efficiently, it is necessary to predict the nitrogen (N) bioavailability, which is a challenging matter due to the different physical-chemical characteristics of commercially available OFs. This study aims to evaluate hot-water extractable N as a rapid and cheap chemical indicator of bioavailable N. The trial was conducted on nine animal-based OFs obtained from different raw materials and treatment processes. They were fully characterized and the bioavailable N was determined by a 7-week soil incubation experiment. The results showed that hot-water extractable N underestimated bioavailable N in the case of leather meal based OFs; however, a significant linear regression fitting was achieved (R2 = 0.53). The C:N ratio was also assessed, which showed a negative correlation (−0.87) and a better linear regression fitting (R2 = 0.76) with the bioavailable N, but manifested some limitations in the prediction of leather meal based products. This experiment showed that both hot-water extractable N and C:N ratio can provide useful information for farmers in managing this class of OFs.

In agriculture, the use of soil biodegradable mulch films could represent an eco-friendly alternative to conventional plastic films. However, soil biodegradable mulch films incorporated into the soil through tillage, being not only a physical but also a biogeochemical input, is expected to influence the soil quality by affecting its functions. Therefore, the eco-compatibility of these biodegradable plastics needs to be evaluated for their impact on different soil functions. To understand the effect of biodegradable plastics on soil quality (i.e. microbial biomass, nitrogen cycle, and activity of soil enzymes involved in the biochemical processes of carbon and nitrogen), we added increasing quantities of biodegradable plastics in two different soils: a loamy (Cambisol) and sandy (Arenosol) soil. The results highlight that the carbon added through the biodegradable plastics influenced the processes linked to carbon and nitrogen cycles. Significant effects were observed mainly with the highest dose of biodegradable plastics added (1%), resulting in a higher growth of microbial biomass, increased carbon mineralisation, and increased immobilisation of available nitrogen. The results also underline the importance of evaluating the impact of biodegradable plastics in different soils because all the processes considered are also influenced also by soil physicochemical characteristics.