Soil quality (SQ) pertains to the intricate and ongoing capacity of soil to function as a thriving ecosystem that supports the growth of plants and animals. However, there is a limited understanding of SQ assessment in mixed forest plantations. Therefore, we formulated and tested the hypothesis that the inclusion of a nitrogen-fixing tree species (such as Acacia mangium) improves SQ indicators in mixed treatments involving Eucalyptus trees. To evaluate the changes in SQ, we conducted a field experiment that employed the Soil Management Assessment Framework (SMAF) tool to analyze pure and mixed plantations of Eucalyptus grandis and A. mangium. Soil samples were collected at a depth of 0–20 cm from different treatments, including pure E. grandis without nitrogen fertilization (E), pure A. mangium (A), pure E. grandis with nitrogen fertilization (E + N), and mixed E. grandis and A. mangium (E + A). Sampling took place at 27 and 39 months after planting. We selected seven indicators of SQ: two biological indicators (soil microbial biomass carbon and β-glucosidase enzyme activity), four chemical indicators (soil organic carbon, pH, available phosphorus, and potassium), and one physical indicator (bulk density). By applying the SMAF tool, we determined the SQ scores for each indicator. The results revealed that E + A stands exhibited higher SMAF scores than pure stands, particularly in terms of pH (0.49 and 0.52 at 27 and 39 months, respectively) and phosphorus levels (0.84 and 0.82, at 27 and 39 months), respectively. Forest management practices and the sampling period had the most pronounced impact on biological and chemical indicators. Notably, significant positive correlations were observed between SMAF scores and pH, available phosphorus content, enzymes, soil organic carbon, and microbial biomass in both sampling periods. This study effectively provided novel information that introducing a nitrogen-fixing tree species in combination with eucalyptus trees enhances SQ, as indicated by the SMAF tool, which could reduce the need for external inputs (e.g., mineral fertilizers) by the farmers. Future studies should analyze the effects of A. mangium not only with other E. grandis varieties but also with other forestry essences.

Biological soil crusts (BSC) are commonly found in soils in the drylands regions, which can influence stabilization, water retention, nutrient cycling (particularly carbon (C) and nitrogen (N) dynamics), and several ecological processes. However, the composition of BSC in Brazilian soils undergoing the desertification process remains poorly understood. This study aimed to characterize the bacterial community in BSC formed in a Brazilian semiarid region under the desertification process. Thus, a highly desertified region was selected from which 34 BSC samples were collected. The total DNA of the BSC was extracted from 0.5 g samples, and the bacterial community was sequenced by a Next Generation Sequencing (NGS) platform (Miseq – Illumina®) using universal primers (515F and 806R). Bioinformatic analysis was carried out in QIIME (v.1.9), and the Operational Taxonomic Units (OTU) table was constructed following the Sumaclust methodology. The pH of BSC, C, N, and phosphorus contents was analyzed. Our study identified a diverse bacterial community in the BSCs. Cyanobacteria, Chloroflexi, and Proteobacteria phyla presented the greatest relative abundance (%) across the samples. Cyanobacteria were dominated by the orders Nostocales and Leptolyngbyales. The prediction of the putative functions found that mostf OTU were related to phototrophy, photosynthetic cyanobacteria, and photoautotrophy. The study found correlations between bacterial phyla and BSC properties, with Cyanobacteria positively related to C. Chloroflexi, Armatimonadetes, and WPS-2 were negatively correlated with C and N contents. These results suggest the critical roles bacteria communities play in BSCs from the Caatinga biome and highlight the potential impact of environmental factors on their diversity and functions.

Summary: Globally, the use of biological products, including biological control agents, biofertilizers, and bioinoculants, has increased significantly as a strategy to reduce dependence on synthetic inputs and promote sustainable agriculture. However, its effects on soil health are still poorly explored. Therefore, this study aimed to analyse the multifunctionality of biological products in agriculture, focusing on soil health, using a systematic review and bibliometric analysis approach. This analysis involves summarizing their mechanisms of action, categories, and impacts. Parameters such as the number of publications per year, the most cited articles, the frequency of keywords and international scientific collaboration networks between countries were analysed. The results showed an expansion in the number of publications on biological products and biological products over the years, with a significant growth in recent years, with emphasis on Brazil and Russia. The most frequent keywords include ‘biological products’, ‘biological product’, ‘soil’, ‘fungi’, ‘bacteria’, and ‘biological control’, and the most cited articles address topics such as the use of Azospirillum sp. in agriculture, the combined application of biological products to control soil diseases, and the inoculation of seeds with Bacillus subtilis. Although few studies have directly evaluated soil health, the results indicate that biological products are related to improvements in soil health, which stimulate the microbiota and promote greater productivity, thereby positively impacting the physical and chemical properties, highlighting the importance of an integrated approach for soil health.