# Sustainable Agriculture and Soil Conservation
## 2 Overview of This Special Issue  
This SI collects 12 original contributions focused on soil use and management, soil conservation, as well as on the impact of some pollutants on the soil. Specifically, the SI collects nine research papers [10; 11; 12; 13; 14; 15; 16; 17; 18], two reviews [19; 20] and one methodological work [21]. Eight of the twelve manuscripts considered the effects of soil use and management (topic I) [10; 11; 12; 13; 14; 15; 16; 21], while the remaining four [17; 18; 19; 20] evaluated the impact of some soil contaminants (e.g., crude oil, tungsten, copper and polycyclic aromatic hydrocarbons) (topic II). This grouping was used to detail the contents and for the reader's usefulness. Regarding the aforementioned nine investigations (i.e., research papers), seven were carried out in the field [10; 11; 12; 13; 14; 15; 16], while the others accounted for pot [17] or microcosm [18] experiments. From a geographical point of view, five \"field open-air\" investigations were carried out in Italy (three in the south [12; 13; 16], one in the center [15] and one in the north [10] of Italy), while the remaining investigations were in Brazil [14] and China [11]. Topic I comprises eight papers. [PERSON] et al. [10] investigated the short-term effects of digestate on soil properties through a holistic approach, thus investigating the soil's physical, chemical and microbiological properties and their interactions. The digestate effects were evaluated in the two maize growing seasons within a 2-year maize-trticulate rotation to feed the biogas plant. The main results showed that the digestate (1) increased the soil's total organic C, total N and K contents, (2) did not affect the soil bulk density while transiently improving the soil aggregate stability, (3) decreased the soil transmission pores (50-500 \(\upmu\)m size) proportion as well as increasing the fissures (>500 \(\upmu\)m), (4) only transiently affected the soil's microbial community and did not cause soil contamination from Clostridaceae-related bacteria, (5) significantly impaired seed germination when applied at low dilution ratios and (6) did not improve the crop yield, as it was similar to usual mineral fertilization. In the context of energy crop farming, the authors concluded that the agronomic recycling and usage of digestate from biogas production assured a sustainable crop yield and soil quality. Therefore, digestate was confirmed as a valid resource for sustainable management of the soil's fertility. [PERSON] et al. [11] investigated the prediction of soil organic matter (SOM) from visible and near-infrared (VNIR) spectra, taking into account the presence of nonlinear relationships and spatial heterogeneity conditions. Specifically, they combined the proposed partial least squares-based multivariate adaptive regression spline (PLS-MARS) method and a regional multivariable associate rule mining and Rank-Kennard-Stone method (MVARC-R-S) to construct a nonlinear prediction model to realize local optimality considering spatial heterogeneity. The method, which was applied and validated for a case study in Hubei (China), was able to filter the spatial autocorrelation present in the investigated area. In addition, it showed improvements compared with some available methods in terms of accuracy and robustness, suggesting the reliability of the proposed prediction model. [PERSON] et al. [12] compared four soil management strategies at a peach orchard, namely (1) completely tilled (control); (2) multiched with reusable reflective plastic film; (3) multiching with a leguminous cover crop flattened after the peach fruit set; (4) completely tilled and irrigated with the water volumes of the treatment with reflective mulching. The effects on the soil features, water use efficiency (WUE), tree functionality, fruit growth and quality, yield and water productivity were investigated.