From the perspective of finding new, more environmental-friendly methods for the stabilization of sewage sludge to be used in agriculture, sludge treated with 15% bentonite, vermiculite or biochar was investigated as a soil amendment for white clover (Trifolium repens L.) growth, by means of a pot experiment. The sludge treatments, which were applied to two soils (an acid and an alkaline soil), in three replications, were the addition of 2% (≈80 Mg ha⁻¹) treated sludge with the clay minerals or biochar, as well as limed or untreated (air-dried) sludge (for comparison reasons). Additional treatments with inorganic fertilization or neither organic nor inorganic fertilization (control) were also included. The application of 2% sludge to both soils significantly increased salinity compared to the control, which remained below harmful levels for sensitive crops, except for the case of untreated sludge. Furthermore, it significantly increased the soil-available macronutrients N, P and K, and micronutrients Cu, Zn (several times, especially in the case of untreated sludge) and B (up to three times) compared with the control. Moreover, the pH of the acid soil was improved, except for the case of limed sludge, where an undesirable pH increase close to 8.5 was observed. Addition of the treated sludge with the clay minerals or biochar and untreated sludge to the acid and alkaline soil significantly increased the aboveground biomass yield of white clover by 117–233% and 114–153%, respectively, compared to the control, whereas limed sludge had no effect. Plant nutrient uptake increased as well. In general, the effect of sludge on soil microbiological properties and arbuscular mycorrhizal fungal root colonization was ambiguous. It was concluded that 2% soil addition of sewage sludge treated with 15% bentonite, vermiculite or biochar could improve soil fertility and enhance plant growth; however, caution is needed with respect to potential risks of soil salinization or Zn and B phytotoxicities.

Tulipa scardica (Balkan endemic) was last recorded in Greece in 1896, possibly attributed to longstanding taxonomic ambiguity, as it has frequently been considered as conspecific with T. gesneriana or T. undulatifolia. In the present study we aimed to investigate the historical Greek locality of T. scardica and to reassess its taxonomic status in comparison with the closely related T. undulatifolia (also native to Greece and member of T. scardica complex). Targeted field surveys were conducted to verify the presence of T. scardica in Greece. The newly identified tulip population was subjected to an integrated analytic approach, including qualitative and quantitative morphological assessment, seed micromorphology, DNA barcoding, karyological investigation, and habitat/soil properties analyses. These datasets were comparatively evaluated against four reference populations of T. undulatifolia. Molecular data did not provide consistent species-level resolution, whereas morphological and karyological evidence statistically supported their distinction. Mitotic metaphase chromosomes of T. scardica were documented herein for the first time, while first-time scanning electron microscopy (SEM) analysis revealed the presence of different types of stomatal complexes in seed coats of both taxa. In addition, soil parameters differed between the examined taxa, and those of the rediscovered population were consistent with habitat preferences of T. scardica. Although both taxa exhibited considerable variability, the combined evidence derived from the present study strongly supported the rediscovery of T. scardica in Greece after approximately 130 years, unless proven otherwise in a wider context across its Balkan range.