Qualitative soil quality assessment is efficient in a grazing system with or without trees.

BACKGROUND: Soil quality (SQ) assessment is affected by methods that convert data sets into indices, and such analyses are expensive and time-consuming. Qualitative SQ assessments are faster and cheaper than quantitative methods and they can be repeated to monitor SQ in crop and pasture systems. We evaluated SQ using qualitative and quantitative SQ indicators of two grazing systems under Voisin rational grazing (VRG) with trees (WT) or without trees (NT). We took an adjacent native forest as a reference and we used principal component analysis (PCA) to compare the accuracy of the assessment methods. RESULTS: According to the set of indicators used for quantitative assessment, the WT system and the Forest had higher SQ than other systems as a result of higher values of soil physical and chemical indicators. This the reflected better performance of soil in functions related to structural support, nutrient cycling and biological productivity. According to the set of indicators used for qualitative assessment, the WT system showed better SQ than the NT areas because of the higher scores of all indicators and better performance of the soil functions, and those values were close to the Forest in the indicators. PCA applied to integrate the data of qualitative and quantitative indicators indicated that SQ in WT was similar to Forest. CONCLUSION: The qualitative evaluation was as efficient as the quantitative evaluation for SQ assessment in VRG areas with and without trees. Its use can promote farmers' autonomy and the development of skills to identify environmental factors that help to evaluate their practices. © 2023 Society of Chemical Industry.

Crop rotation reduces the frequency of anaerobic soil bacteria in Red Latosol of Brazil.

Crop diversity affects the processes of soil physical structuring and most likely provokes changes in the frequencies of soil microbial communities. The study was conducted for soil prokaryotic diversity sequencing 16S rDNA genes from a 25-year no-tillage experiment comprised of two crop systems: crop succession (Triticum aestivum-Glycine max) and rotation (Vicia sativa-Zea mays-Avena sativa-Glycine max-Triticum aestivum-Glycine max). The hypothesis was that a crop system with higher crop diversification (rotation) would affect the frequencies of prokaryotic taxa against a less diverse crop system (succession) altering the major soil functions guided by bacterial diversity. Soils in both crop systems were dominated by Proteobacteria (31%), Acidobacteria (23%), Actinobacteria (10%), and Gemmatimonadetes (7.2%), among other common copiotrophic soil bacteria. Crop systems did not affect the richness and diversity indexes of soil bacteria and soil archaea. However, the crop rotation system reduced only the frequencies of anaerobic metabolism bacteria Chloroacidobacteria, Holophagae, Spirochaetes, Euryarchaeota, and Crenarchaeota. It can be concluded that crop succession, a system that is poorer in root diversity over time, may have conditioned the soil to lower oxygen diffusion and built up ecological niches that suitable for anaerobic bacteria tolerating lower levels of oxygen. On the other hand, it appeared that crop rotation has restructured the soil over the years while enabling copiotrophic aerobic bacteria to dominate the soil ecosystem. The changes prompted by crop succession have implications for efficient soil organic matter decomposition, reduced greenhouse gas emissions, higher root activity, and overall soil productivity, which compromise to agriculture sustainability.