Herein, we applied DNA barcoding for the genetic characterization of Sideritis syriaca subsp. syriaca (Lamiaceae; threatened local Cretan endemic plant) using seven molecular markers of cpDNA. Five fertilization schemes were evaluated comparatively in a pilot cultivation in Crete. Conventional inorganic fertilizers (ChFs), integrated nutrient management (INM) fertilizers, and two biostimulants were utilized (foliar and soil application). Plant growth, leaf chlorophyll fluorescence, and color were assessed and leaf content of chlorophyll, key antioxidants (carotenoids, flavonoids, phenols), and nutrients were evaluated. Fertilization schemes induced distinct differences in leaf shape, altering quality characteristics. INM-foliar and ChF-soil application promoted yield, without affecting tissue water content or biomass partitioning to inflorescences. ChF-foliar application was the most stimulatory treatment when the primary target was enhanced antioxidant contents while INM-biostimulant was the least effective one. However, when the primary target is yield, INM, especially by foliar application, and ChF, by soil application, ought to be employed. New DNA sequence datasets for the plastid regions of petB/petD, rpoC1, psbK-psbI, and atpF/atpH were deposited in the GenBank for S. syriaca subsp. syriaca while the molecular markers rbcL, trnL/trnF, and psbA/trnH were compared to those of another 15 Sideritis species retrieved from the GenBank, constructing a phylogenetic tree to show their genetic relatedness.

Origanum dictamnus L. (Lamiaceae), a local endemic plant of Crete (Greece), creates polysaccharide-containing subcuticular compartments presenting biological activity against phytopathogenic fungi, and, among others, significantly affects the fungal cell wall polysaccharides. This field study introduces a fertilization scheme for O. dictamnus, which was developed and refined to optimize the yield as well as critical herbal quality aspects. Five fertilization schemes were investigated, based on a polysaccharide-based Integrated Nutrient Management (INM), a mixture of conventional inorganic fertilizers (ChF) and two biostimulants (not algae) via foliar and soil application. Plant growth, together with leaf chlorophyll fluorescence and color (SPAD meter, DA meter, Chroma Meter) were determined. The leaf content of chlorophyll, three critical antioxidant compounds (carotenoids, flavonoids, phenols) and nutrients were also assessed. Considering all three antioxidants together, the enhanced efficiency, non-toxic, water-soluble, polysaccharide-based INM by foliar application was the most stimulatory scheme, playing an important role in plant growth and development. The present field study provides, for the first time, baseline fertilization data improving key herbal quality features in O. dictamnus and unravels the attainment of high antioxidant properties. The latter may be exploited in favor of its further utilization as a raw material for tea preparation, medicinal purposes, natural food flavoring and/or food preservative.

Due to the combined climate and biodiversity crisis, the sustainable utilization of phytogenetic resources stands as a one-way alternative, while nutrient management strategies are gaining an increasing role in agriculture. Building on previous studies regarding the Endangered local endemic of Crete (Greece) Carlina diae (Asteraceae), with medicinal and ornamental value, this investigation focused on its pilot cultivation and fertilization (foliar or soil application). Foliar application comprised inorganic fertilization (conventional) or integrated nutrient management (INM). Soil application consisted of conventional inorganic fertilizers, biostimulants, or INM with biostimulants. Above-ground biomass content of nutrients, leaf chlorophyll fluorescence, and color parameters (SPAD meter, DA meter, Chroma Meter) were estimated. The leaf chlorophyll content, three key antioxidant compounds, and nutrient titers were also determined. The fertilization scheme did not influence plant growth and visually perceived quality (leaf color and shape). Notably, foliar INM fertilization increased biomass partitioning to inflorescences (harvestable organs for either medicinal or ornamental purposes) and decreased tissue water content (facilitating processing). Considering all three antioxidants together, INM with biostimulant appeared the optimum scheme, being associated with the highest (carotenoids, phenolics) or the second highest (flavonoid) content. In C. diae, therefore, INM fertilization was optimal for upgrading yield (foliar) and herbal quality in terms of antioxidant profile (INM with biostimulant), which might be embraced as an eco-friendly approach for high-quality yields.

In the perspective of finding environmental-friendly and cheap methods for the stabilization of sewage sludge to be used in agriculture, sludge treated with bentonite, mixed saponite-attapulgite, or zeolite was evaluated as soil amendment for ryegrass (Lolium perenne L.) growth. The clay minerals or Ca(OH)2 were added to dewatered sewage sludge at rates 30% or 10%, respectively. Control sample without additives was also prepared. All materials were added to two soils (alkaline and acid) at rates 10 and 30 g kg−1 and used in a pot experiment with ryegrass. Additional treatments of inorganic N-P-K fertilization and no fertilization (control) were included. For both soils, the amendments affected differentially pH and increased their electrical conductivity (below 4 dS m−1). Moreover, they increased available NO3-N, P, and K compared to control, with their respective concentrations being 23–107, 29–79, and 132–675 mg kg−1 for the alkaline and 10–29, 33–87, and 70–570 mg kg−1 for the acid soil. Total concentrations of heavy metals were below the permissible levels. Basal respiration and microbial biomass C responded to application of all amendments at the highest rate. Both rates increased ryegrass’s aboveground-biomass yield, which was 37–67% and 54–79% higher than control for the lower and higher rate, respectively, as nutrients’ uptake. Sewage sludge stabilized with certain clay minerals could be used in agriculture with application rates less than 30 g kg−1 (≈120 Mg ha−1) to be considered both beneficial for crops’ growth and safe, regarding soil salinization, NO3-N leaching, P, and heavy metals build-up risks.

Domestication of wild plant species of interest coupled with introduction of pilot cultivation practices and appropriate fertilization schemes could be an efficient alternative for addressing sustainable exploitation needs of threatened and/or declining wild phytogenetic resources. In this field study focusing on four threatened wild-growing plants ( Carlina diae , Origanum dictamnus , Origanum microphyllum , and Sideritis syriaca subsp. syriaca ) confined to Crete (local endemics), the effects of three types of fertilization (inorganic, plain semi-organic or co-applied with commercial biostimulants based on edible raw plant materials) by two methods (foliar/soil application) on plants’ growth were investigated. Specifically, plant parameters such as aboveground biomass yield, content and uptake of nutrients by plants as well as arbuscular mycorrhizal fungi root colonization were evaluated. Results revealed a distinction in plants’ multi-elemental stoichiometry, except in the case of Origanum species, in which the variance of their ionomics showed a significant overlap. The elements most closely related to yield were K and Zn, while Pearson tests showed various correlations between studied essential nutrients. Among them, the positive correlations between B and Ca, and Mg (with r value up to 0.9 at p ≤ 0.001, in all studied species except O. dictamnus ); the negative correlations between K and Mg (in O. dictamnus and S. syriaca subsp. Syriaca , r = − 0.5 at p ≤ 0.001); and the positive correlation patterns between Fe and Mn, or Cu and Zn, respectively (in all studied species) , were observed. Biostimulant application alone or in combination with semi-organic fertilizers increased the yield of C. diae (up to 161%) and of the two Origanum species studied (up to 70% and 68% for O. dictamnus and for O. microphyllum , respectively), while inorganic fertilization was beneficial for S. syriaca subsp. syriaca (up to 170% increase) and O. microphyllum (up to 79% increase). However, no solid conclusions could be derived in respect of the preference of the four species for any fertilizers' application method (foliar or by soil).

Wild phytogenetic resources are threatened by overexploitation. This pressure on species and natural ecosystems can be alleviated in part by recruiting and domesticating wild-growing species under pilot cultivation with tailor-made fertilization schemes. This study focused on the pilot cultivation of Origanum microphyllum—a critically endangered local endemic plant of Crete, Greece—investigating the effect of conventional and integrated nutrient management (ΙΝΜ) fertilizers by foliar or root application and biostimulant. Above-ground biomass together with leaf chlorophyll fluorescence and color (SPAD meter, DA meter, Chroma Meter) were determined. Leaf chlorophyll, antioxidant compound (carotenoids, phenols, flavonoids), and nutrient contents were also assessed. The results showed that fertilization did not significantly affect plant growth and leaf nutrient content. Root fertilization was associated with greener leaves compared to foliar. The same trend was generally evident for antioxidant compound content. The small size of leaves may have impeded the efficiency of the foliar application. In conclusion, root application of conventional or INM fertilizers seems more suitable to promote visual quality and herbal antioxidant profile of O. microphyllum, than the foliar one.

The domestication of wild-growing plants, including cultivation and fertilization protocols, is able to alleviate the ecological risks posed by the uncontrolled harvesting of range-restricted local endemic plants. In this field study focused on Verbascum arcturus, a vulnerable local endemic of Crete (Greece), the effect of two kinds of fertilization applied by two methods (foliar/root) was investigated. The foliar application included conventional or integrated nutrient management (INM) fertilization. Root application included the application of conventional fertilizers, biostimulants, or INM with biostimulants. Several properties of plant growth, physiology and nutrition were determined. The results showed that fertilization treatment affected neither leaf color and shape nor plant growth, morphology, dry mass partitioning or nutrient content. However, both kinds of foliar-applied fertilization enhanced Zn and B in leaves and soil-applied biostimulant increased leaf Ca. Considering both chlorophyll and antioxidant compounds’ content, foliar application of the INM fertilizers, as well as soil application of the conventional fertilizers or biostimulants, could be considered as accepted options. This study reports for the first time an assessment of the total phenolic and flavonoids content evidenced in V. arcturus and encourages the use of fertilization in promoting the herbal antioxidant profile without compromising visual quality or yield. The findings of this study could be considered as a documented contribution toward the sustainable exploitation of V. arcturus.

Liquid dairy cattle (Bos taurus) manure effect on corn (Zea mays L.) yield and nutrients’ uptake and soil fertility were studied, in comparison to the crop’s common and recommended inorganic fertilization, by means of a 5-year field experiment. The treatments applied each year in the same plots were: (i) manure, (ii) common inorganic fertilization, (iii) recommended inorganic fertilization, and (iv) no fertilization. Each year from each plot, surface soil samples were collected before sowing, corn aboveground biomass was collected at silage, they were analyzed, and grain yield was determined at harvest. Upon all kinds of fertilization, corn silage yield increased in comparison to control and ranged between 51 and 194, 50 and 190, and 39 and 189% for the manure, recommended, and common inorganic fertilization treatment, respectively. Similarly, grain yield and the macro- and micronutrients’ plant uptake were increased. Soil fertility improved regarding the NO3-N, which upon organic or inorganic fertilization increased 10–46% in comparison to the control. Manure application significantly increased K by 32–81%. However, in the case of P, an excessive increase was observed, which was two to three times higher than the inorganic fertilization (30–44 mg kg−1). Consequently, repeated annual applications of liquid cattle manure to soil can enhance crop yield, nutrients’ uptake, and soil fertility, at levels higher or similar to the common or recommended inorganic fertilization for the crop. However, the possibility of P build up should also be considered.

Preserving sewage sludge’s N is important for its agronomic use and this could possibly be achieved by treating sludge with certain clay minerals. Nine clay minerals and additionally Ca(OH)2 were added to dewatered sewage sludge at 0–30 % rates (wet weight basis) (treatments). After 70 days of equilibration, all mixtures were analyzed for certain properties and the mineral-sludge mixtures which showed the highest microbial load reduction were further assayed, along with the limed and untreated sludge. From all minerals’ treatments, the fecal indicators of sludge treated with 30% of two bentonites, attapulgite, saponite–attapulgite, and zeolite decreased considerably compared to the control. These treatments were performed also well regarding sludge’s retention capacity of available inorganic N, with the attapulgite and zeolite treatments containing the significantly highest amounts of NO3–N and NH4–N, respectively. For the water-soluble inorganic N, similar results were obtained for the zeolite treatment, whereas the treatments with the two bentonites had the significantly highest NO3–N content. Also, considerable amounts of water-soluble P were obtained in all cases of the treated sludge with minerals. Limed sludge had the lowest content of the water-soluble inorganic N and P. As far as the micronutrients are concerned, only Zn and B were detectable in the water-soluble fraction of all five minerals’ treatments. The heavy metals, which regulate sludge’s agronomic use, were far below the respective permissible limits and lower than the untreated sludge, except for Ni and Cr in the attapulgite and saponite–attapulgite treatments. In conclusion, certain clay minerals, i.e., bentonite, attapulgite, mixed clay of saponite and attapulgite, and zeolite, seem promising materials for the stabilization of sewage sludge in the perspective of using them as a fertilizer. In addition, they seem to have higher fertilizing value than limed sludge. However, environmental (in respect of Ni and Cr) and agricultural (in respect of Zn and B) impacts must be considered.

Purpose Preserving sewage sludge's N is important for its agronomic use, although N losses are not considered by the most common sludge's stabilization processes. This could possibly be achieved by treating sludge with certain clay minerals, which could retain N as NH4 + into their structure. Methods Nine clay minerals, i.e. low and high grade bentonite, low and high grade bentonite treated with Na2CO3, saponite, attapulgite, mixed clay of saponite and attapulgite, thermally modified attapulgite and zeolite (i.e. clinoptilolite), and Ca(OH)2 were added to dewatered sewage sludge at rates of 0, 10, 20 and 30% (wet weight basis) (treatments). The mixtures were equilibrated for 70 days and analyzed for certain properties. Results The microbial indicators (load) of sludge treated with both untreated bentonite, attapulgite, mixed clay of saponite and attapulgite and zeolite, added at the rate of 30%, decreased compared to the control, drastically in certain cases (100%), and as it was expected, were not detectable in all Ca(OH)2 treatments. All the aforementioned minerals' treatments were performed also well regarding sludge's retention capacity of inorganic N, with the attapulgite and zeolite treatments containing the significantly highest amounts of NO3-N and NH4-N, respectively. On the other hand, the treatments with both bentonites treated with Na2CO3 had the lowest inorganic N concentration, which was similar to that of the Ca(OH)2 treatment. Conclusions Certain clay minerals, such as natural bentonite, attapulgite, mixed clay of saponite and attapulgite and zeolite, seem promising materials for the stabilization of sewage sludge and preservation of its N content.

The effect of sewage sludge, stabilized with steelmaking slag, on soil chemical properties and fertility and on wheat (Triticum aestivum L) growth was evaluated. Dewatered sewage sludge [75% (wet weight basis)] stabilized with steelmaking slag (25%) and three soils with different pH values were used in a pot experiment with winter wheat. The following treatments were applied: (i) sludge addition of 30 g kg(-1) (approximate to 120 Mg ha(-1), rate equivalent to the common inorganic N fertilization for wheat, based on sludge's water soluble NO3-N), (ii) sludge addition of 10 g kg(-1) (approximate to 140 Mg ha(-1), rate equivalent to the common inorganic N fertilization for wheat, based on sludge's Kjeldahl-N), (iii) addition of the common inorganic N fertilization for wheat (120 kg N ha(-1)) as NH4NO3, (iv) control (no fertilizer, no sludge). Sludge application at both rates to all soils resulted in a significant increase of pH, electrical conductivity of the saturation extract (ECse) and soil available NO3-N and P, in comparison to the other two treatments and this increase remained constant till the end of the pot experiment. In sludge treatments pH did not exceed the critical value of 8.5, whereas ECse, although it did not reach the limit of 4 dS m(-1), exceeded the value of 2 dS m(-1) at the rate of 30 g kg(-1). Concentrations of heavy metals, which regulate the agronomic use of sewage sludge according to the established legislation, ranged from not detectable to lower than the respective permissible levels. Both rates of sludge's addition in all soils improved wheat's growth, as judged by the significant increase of the aboveground biomass yield and the total plant uptake of almost all nutrients, compared to the other two treatments. It was concluded that sewage sludge stabilized with steelmaking slag could be used in agriculture, applied at rates based on sludge's Kjeldahl-N content and crop's demand for N. However, potential environmental impacts must also be considered. (C) 2017 Elsevier Ltd. All rights reserved.