Abstract
Conventional fertilization practices in agroecosystems concern the supply of bioavailable nutrients, such as mineral fertilizers. A consolidated alternative to restoring the long-term fertility of agricultural soils is their amendment with organic fertilizers. Soil amendment with biowaste compost or sewage sludge represents a sustainable strategy to avoid the landfilling of organic matter derived from urban waste and sewage sludge. This study aims at validating the use of quality biowaste compost and sewage sludge from secondary sedimentation (alone or in combination with mineral fertilizers) in a Mediterranean agroecosystem and their effects on soil chemical and biological quality, with a view to verifying the maintenance of soil fertility and functionality. In particular, the dynamics of soil organic matter, pH, potentially toxic elements and microbial community functionality were assessed, in experimental mesocosms, during 6 months of incubation. The research showed that, while soil amendment with biowaste compost induces positive effects on soil organic matter and phosphorous concentrations, as well as on microbial community functionality, the amendment with the selected sewage sludge does not determine any benefit to the microbial community or any danger in relation to soil potentially toxic element concentrations and toxicity. The quantity of sewage sludge employed, chosen according to regional directives, was thus not enough to stimulate the edaphic microflora activity.
Highlights
Soil organic matter (SOM) plays a major role at the global level in the context of climate change [1]
The 6 exposure conditions included the following scenarios (Table S1): (1) untreated reference soil (UNT), (2) soil amended with biowaste compost (BC) (CMP); (3) soil amended with sewage sludge (SS) (FNG), (4) soil amended with mineral NPK fertilizer (MIN), (5) soil treated with BC and mineral fertilizers (MFs) at half doses of those supplied in CMP and mineral fertilizer (MIN) treatments (C + M), and (6) soil treated with SS and MF at half doses of those supplied in FNG and MIN treatments (F + M)
The non-metric multidimensional scaling (NMDS) with the superimposition of confidence ellipses (Figure 1) clearly separated CMP and partly C + M treatments from the others (FNG, F + M, MIN and untreated soil (UNT)), with soil respiration, hydrolase activity, and microbial C and N relatively more abundant in mesocosms amended with BC
Summary
Soil organic matter (SOM) plays a major role at the global level in the context of climate change [1]. A loss of soil organic carbon (SOC) contributes to a reduction of soil productivity, and to climate change, since the carbon is partly lost through. SOM indirectly contributes to agro-ecosystem productivity and to food security, maintaining the fertility of cultivated soils, providing energy for edaphic microorganisms that allow the functioning of agroecosystems [3], and making inorganic and organic pollutants less available [4,5]. There is the need to implement management options that allow enhancing soil fertility and increasing SOC stocks, contributing to climate change mitigation. Within the Mediterranean area, facing a high risk of desertification, the increase in SOC is pivotal in counteracting the current trends of soil erosion and loss of fertility with the consequent long-term effects on ecosystem viabilities [6].
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