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Reducing the deleterious effects of intensive tillage and fertilization on ecosystem integrity and human health is challenging for sustainable agriculture. The use of cover crops has been advocated as a suitable technique for this purpose, but scientific evidence to support this has been scarce. After four years and a complete rotation, including wheat, maize, and green pea as main crops in a ploughing system, we investigated the respective and combined effects of cover crops and nitrogen fertilization on soil chemical and biological properties using a controlled experiment combining soil chemical analyses, high‐throughput sequencing and community level physiological profiles. Cover crops impeded the soil carbon and nitrogen depletion induced by intensive tillage, not only in the topsoil but also within deeper soil horizons, where more specialized bacterial communities established. Cover crops induced a significant shift in soil bacterial community diversity and composition, which was associated with changes in soil chemical features and bacterial metabolic activities along the entire soil profile. Cover crops enhanced soil resilience to nitrogen fertilization by increasing functional redundancy and complementarity within soil bacterial communities and across soil horizons. Synthesis and applications. In the ploughing systems commonly used for intensive agriculture in Western Europe, the use of cover crops fosters a high functional diversity among soil bacteria and thus can help to achieve a more sustainable agriculture by reducing nitrogen fertilization while maintaining yields.

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Low soil fertility in ultramafic soils limits the efficiency of nickel phytoextraction. Developing more efficient cropping systems for agromining can be achieved by the association of a hyperaccumulator with a legume by enhancing soil fertility. However, legume crops can result sensitive to ultramafic soil conditions, including nickel Ni availability. We assessed here whether Lens culinaris is adapted to ultramafic environments by growing on soils displaying a wide range of Ni concentrations and consequently producing functional nodules. The soil was enriched with different Ni concentrations ([Ni]) (0-90 mg Ni kg À1). Natural 15 N abundance was used to assess N 2 fixation (%Ndfa). Biotic parameters were investigated (nodule number, Ni, carbon and nitrogen concentrations, plant biomass. . .). Soil parameters were investigated (total [Ni], DTPA-extractable Ni, C and N concentrations. . .). Most of the physicochemical and biological parameters were significantly affected by the increased soil [Ni]. Nodule numbers per plant was lower under high [Ni] than control (soil without Ni). Nodules lost their capacities to fix N 2 under high Ni addition (90 mg Ni kg À1). For many parameters, there were no significant differences between control and treatments up to 60 mg of Ni kg À1 added to the soil. Lentil is able to grow on a soil containing amounts of Ni-DTPA similar to those generally found in serpentine soils. It could be used in association with a hyperaccumulator plant as a nitrogen provider in order to optimize Ni agromining. 2016 Elsevier B.V. All rights reserved.

The environment is witnessing a downgrade caused by the amelioration of the industrial and agricultural sectors, namely, soil and sediment compartments. For those reasons, a comparative study was done between soil cores and sediments taken from two locations in the Qaraaoun reservoir, Lebanon. The soil cores were partitioned into several layers. Each layer was analyzed for several physicochemical parameters, such as functional groups, particle size distribution, ζ-potential, texture, pH, electric conductivity, total dissolved solids, organic matter, cation exchange capacity, active and total calcareous, available sodium and potassium, and metal content (cadmium, copper, and lead). The metal content of each site was linked to soil composition and characteristics. The two sites showed distinguishable characteristics for features such as organic matter, pH, mineral fraction, calcareous, and metal content. The samples taken toward the south site (Q1), though contain lower organic matter than the other but are more calcareous, showed higher metal content in comparison to the other site (Q2) (average metal content of Q1 > Q2; for Cd 3.8 > 1.8 mg/kg, Cu 28.6 > 21.9 mg/kg, Pb 26.7 > 19 mg/kg). However, the metal content in this study did not correlate as much to the organic matter; rather, it was influenced by the location of the samples with respect to the dam, the reservoir's hydrodynamics, the calcareous nature of the soil, and the variation of the industrial and agricultural influence on each site.