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Highlights: [•] Chitin, marigold and anearobic soil disinfestation were better than chemical control. [•] Grass–clover, biofumigation, Cultivit and compost were not effective alternatives yet. [•] All treatments caused yield increases as a consequence of changes in the soil biota. [•] No negative side effects on soil suppressiveness or non-target soil organisms. [•] These treatments could be implemented in arable crop rotations worldwide. [Copyright &y& Elsevier]

Litter decomposition and nutrient mineralization are crucial in agricultural systems to maintain soil fertility and plant growth. Given that these processes are governed by soil microbial activity, agricultural management that affects soil microbial communities may significantly alter rates of decomposition and N release of the same litter. We hypothesized that organic compared to conventional management enhances litter decomposition and litter N release, and that this effect is stronger for litter of low quality (high C:N ratio). We tested these hypotheses using litter from 4 maize cultivars with varying initial litter quality (different C:N ratios and lignocellulose index). These litters were left to decompose in soil with different management history, yet in the same experimental field site. The field experiment consisted of randomized plots with 11 years of organic or conventional agricultural management (organic vs. mineral fertilization). During the 11 years, in year 3 and 4, two specific organic amendments were applied as soil health treatments (SHT: chitin or compost, and a control without SHT). The maize litter was contained in litter bags, buried in the top 10–15 cm soil and collected after 1, 2 and 3 months. We quantified the litter carbon (C) and nitrogen (N) loss, and soil dissolved organic carbon (DOC), mineral and dissolved organic nitrogen (DON) at each sampling time. We also determined the fungal biomass in the decomposing litter after 3 months of decomposition. Litter C loss was higher in soil under organic compared to conventional management, irrespective of litter quality. In contrast, the rate of N release from the litter was determined by initial litter quality (higher N release from low C:N litter) and not by agricultural management. In soil under organic management the concentrations of DOC, mineral N and DON were larger than in conventional managed soil, which may have stimulated microbial activity and therefore, litter decomposition. Fungal biomass in the decomposing litter negatively correlated with the amount of N in the decomposing litter, but was not affected by management system or litter cultivar. Overall, we found that in agroecosystems initial litter quality (C:N) is a main driver of litter N release, whereas soil management is a main driver of decomposing litter C loss. Our results show the importance of integrating both litter quality and soil management to enhance our understanding of litter decomposition and N release, and to harness the ecosystem services provided by crop litter in agricultural fields. In agroecosystems, the main driver of litter C loss is agricultural practice (conventional vs. organic) while litter quality of the cultivar is the main driver of N loss. Agricultural practice and litter quality also influence the microbial community and the availability of soil nutrients which has an effect on the decomposition process. Image 1 • Management is a main driver of litter decomposition regardless of litter quality. • Litter quality, not management, is a main driver of litter nitrogen release. • Organic management enhances litter decomposition. • Cultivar selection based on decomposability traits can be used to enhance C cycling. • No 7 year legacy effects of compost and chitin on litter C and N loss. [ABSTRACT FROM AUTHOR]

We examined the relationship between plant species diversity, productivity and the development of the soil community during early secondary succession on former arable land across Europe. We tested the hypothesis that increasing the initial plant species diversity enhances the biomass production and consequently stimulates soil microbial biomass and abundance of soil invertebrates. We performed five identical field experiments on abandoned arable land in five European countries (CZ, NL, SE, SP and UK) which allowed us to test our hypothesis in a range of climate, soil and other environmental factors that varied between the experimental sites. The initial plant diversity was altered by sowing seed mixtures of mid-successional grassland species with two or five grass species, one or five legumes and one or five forbs. The results of low and high sown diversity treatments were compared with plots that were naturally colonized by species present in the seed bank. In three out of the five field sites, there was no correlation between plant species number and plant biomass production, one site had a positive and the other a negative relation. Treatments with a high diversity seed mixture had a higher biomass than the naturally colonized plots. However, there was no significant difference between high and low sown diversity plots at four out of five sites. The three-year study did not give any evidence of a general bottom-up effect from increased plant biomass on biomass of bacteria, saprophytic fungi or abundance of microarthropods. The biomass of arbuscular mycorrhizal was negatively related to plant biomass. The abundance of nematodes increased after abandonment and was related to plant biomass at four sites. Our results support the hypothesis that plant species diversity may have idiosyncratic effects on soil communities, even though studies on a longer term could reveal time lags in the response to changes in composition and biomass production of plant communities. [ABSTRACT FROM AUTHOR]