Impact of Nutrients and Trace Elements in Soil on Plant Growth: Case of the Second-Generation Energy Crops

This editorial belongs to the Special Issue “Impact of Nutrients and Trace Elements in Soil on Plant Growth: Case of the Second-Generation Energy Crops”.

The harmonious development of renewable energy sources, including biomass, is becoming increasingly important nowadays as a contribution to energy security. In this regard, second-generation energy crops are attracted a special attention. These groups of plants can be cultivated on the different lands including marginal, with receiving lignocellulose biomass used for energy production; a substantial contribution to the alleviation of climate change is ensured if high yields can be sustained [1].

The production of energy crops’ biomass requires appropriate policies to secure long-term support to improve crop productivity and to ensure the environmental, economic, and social benefits of the cropping systems [2]. Additionally, second-generation energy crops are successfully applied in the phytoremediation processes of contaminated lands [3,4,5]. The green technology approach to contaminated sites implies a union of phytoremediation with biomass production, i.e., phytomanagement [6]. In order to benefit the soil and to ensure proper biomass harvest, the production of energy crops has to be supported by soil amendments, PGRs, fertilization, microorganisms, and retaining nutrients. Evaluating the impact of these factors on the production cycle and phytoremediation process from the theoretical and practical points of view is very important. The Special Issue of Agronomy titled “Impact of Nutrients and Trace Elements in Soil on Plant Growth:” Case of the Second-Generation Energy Crops” brought together original scientific articles dealing with these topics.

Stefanovska et al. [7] investigated the short-term effects of soil amendments, such as biochar, sewage sludge, biogas digestate, and hemicellulose waste, on the harvest value as well as the structure, diversity, and function of a nematode community during the production of the second-generation energy crop Miscanthus × giganteus (M × g) on marginal land in a plantation located in Chomutov, the Czech Republic. In total, 28 nematode taxa were identified, including 5 bacterivores genera, 4 fungivores genera, 5 herbivores genera (11 species), 2 omnivores genera, and 5 predators’ genera. The incorporation of amendments affected the nematode food web and resulted in the suppression of plant-parasitic nematodes (PPNs), which is an important finding for multiyear Mxg production.

Šurić et al. [8] researched the impact of application rate of a soil amendment—sewage sludge—on the biomass yield of the energy crop Virginia mallow (Sida hermaphrodita L.) cultivated in the trace elements (TEs) contaminated soil. The following amounts of amendments were under consideration: 1.66, 3.32, and 6.64 t ha⁻¹ DM. Results showed that with increasing the application rate a biomass yield had a positive trend. The incorporation of sewage sludge did not change the content of cellulose in the aboveground biomass; however, this amendment impacted to the content of hemicellulose: it was increased by 2.5% with an application of 6.64 t ha⁻¹ and by 7.5% with an application of 1.66 t ha⁻¹ of sewage sludge, consequently. When the dose of applied sewage sludge increased, the uptake of TEs, i.e., Cu, Ni, and Mo to biomass of Virginia mallow (Sida hermaphrodita L.) decreased.

The influence of several plant-growth-promoting bacteria (PGPB) isolated from TEs-contaminated soil, namely, Stenotrophomonas maltophilia KP-13, Bacillus altitudinis KP-14, Pseudomonas fluorescens KP-16, and their consortia on the phytoremediation of M × g cultivated in the same TEs-contaminated soil was studied in [9]. Contrary to expectations, the effects of PGPB on the biomass harvest were low. The most significant increase was detected in leaves biomass treated with a consortium of tested PGPBs. The phytoparameters, i.e., translocation factor, comprehensive bioconcentration index, and uptake index, were used to characterize the behavior of Cr, Mn, Ni, Cu, Zn, Sr, V, and Pb in the presence of isolates. Plants treated with PGPB strains accumulated minimal concentrations of Cu and Pb in the aboveground biomass, with a tendency for Zn to accumulate in the leaves and stems, and Sr to accumulate in the leaves. The results revealed the combinations of isolates that stimulated the minimal uptake of TEs into the stems with simultaneous increasing of DW. This study provides more insight into the leading factors of M × g phytoremediation supported by PGPB and can be helpful when the crop is cultivated on TEs-contaminated soils of different origins.

Biological carbon sequestration and sustainable nitrogen management are important tools for mitigation and adaptation to climate change. This SI contains two studies conducted in Croatia, where the status of macronutrients (C and N) in agricultural soils and soils contaminated by Hg and Cd were investigated during the growing of M × g. The authors researched the influence of soil amendments (sewage sludge, mycorrhiza, and ash) [10] and the selection of planting material (rhizomes (M × gR) and seedlings (M × gS)) [11] on the yield and N status of M × g leaves. It was shown that over seven years of vegetation (2016–2022), the total soil carbon content (TSCC) was 1.7 times higher in M × gS than in M × gR, which led to the conclusion that in the similar agroecological conditions, seedlings were more preferable over rhizomes because of much bigger carbon sequestration effect [11]. The application of the proximal spectroscopy method in VNIR spectra as a non-destructive method and the suitability of this approach to the determination of N status in the leaf (R² = 0.87) was confirmed; however, the approach did not work for yield (R² = 0.53) [10].

In the above-overviewed articles, the advanced scientific progress and the explored developments are presented. Therefore, we believe that the SI will serve as useful reference material for researchers involved in the production and utilization of the second-generation energy crops and phytoremediation processes.

We would like to express our appreciation and heartfelt thanks to all authors who contributed to the SI.