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Land uses may shift soil biota community composition, and soil chemical traits. Our aims were to assess if the land uses may influence the soil biota community composition and soil chemical traits; if there are differences into soil biota biomass as influenced by land uses; and what are the plant-soil feedback among the land uses, soil biota, and soil chemical traits. We have collected soil samples and extracted soil biota individuals from four different land uses (e.g., natural ecosystem, conventional farming system, agroecological farming system, and fruticulture). Our results have revealed that land uses have influenced soil biota abundance (from 59.0 to 210.12 ind. trap− 1 in the natural ecosystem and fruticulture system, respectively), richness (from 6.5 to 10.5 in the fruticulture system, and natural ecosystem, respectively), diversity (from 1.01 to 1.75 in the conventional farming system, and natural ecosystem, respectively), dominance (from 0.52 to 0.71 in the natural ecosystem, and conventional farming system, respectively), and its biomass. The studied land uses have decreased the soil organic carbon when compared with the natural ecosystem (5.75 g kg− 1). SOC, soil pH, Olsen's available P, Mg2+, K+, and Na+ were the main factors contributing to the variance of the samples accounting for 78% of the data variance. The results of our study highlight the importance of considering land uses as key factors influencing soil biota community and soil chemical traits. Thus, long-term experiments considering land uses (e.g., conventional farming system, fruticulture, and agroecological farming system) may exploit negative effects of land uses on soil biota abundance on the one hand, while positive effects on soil chemical traits on the other hand. [ABSTRACT FROM AUTHOR]

With the expansion of organic agriculture, research is needed to indicate economically and ecologically viable fertilizer options, especially in semiarid regions, with low soil organic matter and nitrogen content. In the Brazilian semiarid region, vermicomposts are widely used by farmers and are scientifically investigated; however, there is no information for millicompost, a new type of organic compound that has shown very promising results in other regions. Thus, this study aimed to analyze the decomposition rate, nutrient release, and microstructure evaluation of vermicomposts from different sources and of millicompost produced from plant residues, with the application of mineral nitrogen-urea and organo-mineral fertilizer in the Brazilian semiarid region. The experimental design was a randomized block in a 4 × 3 factorial scheme, with four replicates; four organic composts (millicompost, commercial vermicompost, vermicompost from bovine manure, vermicompost from goat manure); and three types of fertilization (without fertilizer, with mineral-urea and organo-mineral fertilizer). The organic composts were decomposed using litterbags at the soil surface. The variable's decomposition rate and the nutrient release were evaluated at six-time intervals (0, 30, 60, 90, 120, and 150 days), and microstructure was evaluated at the beginning and the end of the experiment, with scanning electron microscopy (SEM). The highest decomposition was verified for commercial vermicompost rich in macro and micronutrients and with lower P contents. The lignin:N ratio and the initial P content were more important in the permanence of the organic compost in the field than the C:N ratio. Regardless of the organic composts, the use of urea as a mineral fertilizer stimulated decomposition more than the organo-mineral fertilizer. The initial composition of the nutrients was decisive in the dynamics of nutrient release, mass loss, and decomposition of C. There was no pattern in the release order of macronutrients. However, for the micronutrients, the release order was Cu > Fe > Mn, in all treatments. Microstructure analysis is a visual analysis where differences are detected through microphotographs and the biggest difference occurred with millicompost, which showed elongated fibers and fiber bundles, forming a relatively open structure characteristic of the presence of fulvic acid. However, the addition of organo-mineral fertilizer formed agglomerates in compacted micro-portions, helping the mineralization of C and N. [ABSTRACT FROM AUTHOR]

The soil physical-chemical changes in different land uses in a Tropical Cambisol at Apodi Plateau, Northeastern Brazil, were investigated between May 2017 and April 2018. Soil samples were collected at three soil layers (0–5, 5–15, and 15–25 cm) under three land uses: a 6-year agroecological farming system, a 10-year fruticulture farming system, and a 6-year conventional farming system. We evaluated: bulk density, soil porosity, weighted average diameter (WAD), geometric mean diameter (GMD), soil pH, soil organic carbon (SOC), P, and sum of bases. Soil quality index was built by considering four main functions: Water supply and storage, root growth capacity, nutrient cycling, and soil conservation. Our results emphasized the land use influence on the soil physical-chemical traits in a Tropical Cambisol. The PCA analyses showed that SOC, soil porosity, bulk density, WAD, GMD, soil pH, sum of bases, and soil P content were the main factors contributing to the data variance. We found the highest values of soil quality index in the conventional farming system (0.57 ± 0.03). The results highlight the importance to consider land uses that increase the sum of bases, WAD, GMD, and SOC content, and decrease bulk density. Our findings suggest that (1) a conventional farming system with liming and fertilizers' input positively changed soil physical-chemical traits, which in turn improved soil quality in a tropical Cambisol; and (2) by altering soil functions land uses may create a sustainable cycle into the soil profile thus promoting soil quality. [ABSTRACT FROM AUTHOR]