**Preface**

Soil degradation is defined as a change in the soil's health status resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries. Ecological rehabilitation is required when the soil is degraded to such an extent that the land becomes unproductive. However, the types, causes, and characteristics of soil degradation are complicated and require effective and up-to-date technology for soil degradation and soil pollution restoration. The Special Issue aimed to provide a platform for researchers to communicate their research results or latest insights in related fields. It can also serve as a scientific reference for readers engaged in soil degradation remediation.

In this Special Issue, Sun et al. provide an overview of China's experiences and challenges in achieving sustainable agricultural development. Zhao et al. proposed a new standard describing the surface cracking conditions of soda-saline-alkali soil. Cai et al. found that the application of biochar and manure to soil can improve micropore volume and aggregate stability and increase crop yield. According to Qian et al., soil erodibility (K factor) and saturation conductivity (Ks) are the key indicators to evaluate the quality of land reclamation. The Dorocki and Korzeniowska survey showed that heavy metals in the soil of Jaworzyna Krynicka, in the Beskidy Mountains of Poland, were not highly contaminated. Chen et al. combined geostatistics and chemometric methods to analyze the sources and spatial patterns of heavy metal pollution in soil. Wyszkowska et al. suggested that grass composting and corn planting could mitigate the toxic effects of tetracycline on soil bacterial communities. Lin et al. found that farmland consolidation had a significant effect on soil bacterial community structure. Gong et al. showed that different land use types and soil depths had significant effects on soil mineral element content, soil enzyme activity, and the fungal community in karst areas. Li et al. conducted a seven-year fertilization reclamation experiment in a coal mine subsidence area and found that fertilization had a significant impact on soil bacterial community composition and diversity.

In the future, more attention will be paid to the following aspects of soil degradation and restoration: (1) Evaluation criteria and key indicators of soil degradation. (2) Clarification of soil degradation processes from micro-scale to field-scale to regional-scale. (3) Soil–plant microbial responses and feedback in soil degradation and restoration processes. (4) The critical role of soil degradation and restoration under global climate change.

The Special Issue was successfully completed under the organization of Professor Bo Sun, who had a high academic level in soil quality, soil health, and soil biology. Unfortunately, due to an accident, Professor Sun had to leave his love of soil science research forever. This article is dedicated to his memory.

> **Ming Liu and Yan Chen** *Editors*
