The objective of this study was to evaluate the individual and synergic effects of the application of Biochar (B), Humic Substances (HS), and Gypsum (G) on the soil properties of a saline–sodic soil, and plant growth and seed quality (polyphenols, protein and yield) of quinoa. Treatments included (B) 22 t ha⁻¹, (HS) 5 kg ha⁻¹, and (G) 47.7 t ha⁻¹. Two quinoa genotypes from Arid Zones (AZ-51 and AZ-103) were selected and established in eight treatments. The B + HS + G combined treatment resulted in increases in root biomass of 206% and 176% in AZ-51 and AZ-103, respectively. Furthermore, electrical conductivity (ECe), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) decreased significantly in all treated soils. When compared to the control, ESP decreased 11-fold in the G treatment, and 9–13-fold in the B + G; B + HS; and B + HS + G treatments. Similarly, soil microbial biomass increased 112% and 322% in the B + HS + G treatment in AZ-51 and AZ-103 genotypes, respectively. Therefore, it can be concluded that the application of combined amendments (B + HS + G) represents an alternative for reclaiming degraded soils, including saline–sodic soils.

Wildfires are non-controlled large-scale fires of various vegetation types that have long affected the Mediterranean- climate regions, but their increased frequency and severity has led to the degradation of the ecosystems. Particularly in Chile, 147 major wildfires in 2017, were responsible of burning 546 678 ha, which included 28 729 ha of traditional small-scale non irrigated agricultural systems, highlighting the vulnerability of these agricultural soils to wildfires. Soil biological properties are more sensitive to heating than physicochemical properties. Thus, a reduction of microbial communities and associated enzyme activities generally occur in low-intensity fires (< 200 °C). Most significant changes in physicochemical properties of soil occurring in moderately intense fires (250 to 450 °C) are increases of soil pH, nutrient availability, bulk density and soil water repellency, whereas soil aggregate stability and water holding capacity generally decrease. When vegetation cover is completely destroyed by fire, emergency stabilization treatments such as mulching and seeding provide an immediate ground cover to reduce soil erosion and preserve nutrients. Therefore, it is important to define the impacts of wildfire on soil properties of agricultural lands to establish a roadmap to implement an adequate and viable restoration.

The effects of six crop-pasture rotations were evaluated on properties of soil aggregates in a volcanic soil (Humic Haploxerand) of south-central Chile. Rotations that included intensive cropping without pastures, and crops with short- or long-term pastures were maintained for 12 years after which soil samples were taken at 0–5 and 5–10 cm depths for analysis of the C, N and S contents in the different grades of water-stable aggregates. The mean weight diameter of the aggregates was also determined as an indicator of structural stability. The results showed that the rotations which included long-term pastures of alfalfa (Medicago sativa L.) or white clover (Trifolium repens L.) had higher contents of C, N and S in soil and there was a higher concentration of these elements in macro-aggregates (>0.5 mm) than in micro-aggregates (<0.5 mm). Additionally, the rotations with pastures also produced greater structural stability of the soil aggregates. Consequently, crop rotations that included pastures, particularly those of longer duration, improved the soil and were therefore a more sustainable use of the soil resource compared to the more intensive rotations. Additionally, there was evidence of hierarchical organization of the soil structure, which is a previously non-described feature of volcanic soils.

Farm and industrial residues must be adequately managed to avoid negative environmental implications. In this study, our objective was to evaluate (i) the impact of the co-production of vermicompost using grape bagasse and biochar (BC) on the yield and biochemical, chemical, and biological properties of vermicompost; (ii) the effect of BC on earthworms (Eisenia fetida Sav.). The vermicompost was co-produced over 5 months (n = 4 per treatment) using (i) grape bagasse as the substrate, (ii) earthworms (Eisenia fetida Sav.), and (iii) three BCs (eucalyptus sawdust BC, pig manure BC, and carbonaceous material from poultry litter CM) at 2% (w/w). A control without BC was included. The chemical, microbiological (activity and respiration), enzymatic properties, and enzymatic indices were characterized. After the incubation period, vermicompost yield increased with the application of the three BCs (25% on average). The number of adult earthworms was not affected by any of the BCs. Compared to treatments without BC, those with pig manure BC and eucalyptus BC resulted in maintained or significantly decreased enzymatic activity, indicating that the vermicompost was at an advanced stage of maturity. Eucalyptus BC significantly enriched the C content of the vermicompost by 4.3%, maintaining respiration rates at 18% lower than the treatment without BC. Additionally, pig manure BC generated the lowest respiration rate in the vermicompost (20% lower). We conclude that BC has a positive influence on the vermicompost process, stabilizing organic matter (especially pig manure BC) and improving the potential of vermicompost to store C (when high-C-content BCs are applied).

Wastewater treatment generates large amounts of sewage sludge, which when are disposed in highly degraded soils (with a complete loss of the A horizon and a great part of the B horizon), represent an interesting alternative to recover the aggregate level into soil. Within the hierarchy of soil systems, the aggregate level is the one that integrates soil properties that are directly related to soil sustainability. The aim of this study was to determine the effect of different dose of sewage sludge and an annual legume on the structural recovery of a degraded Alfisol. Sludge was added to soil at 0, 15, 30 and 60 t ha-1 in treatments with and without yellow serradela (Ornithopus compressus L.). After 6 months, the following structural indicators were identified: aggregate distribution, water aggregate stability and bulk density (Da). Results showed that the higher the sludge dose the higher the proportion of macroaggregates and their stability, whereas Da decreased. In spite of the short-term study, data showed that there was a positive effect when amendments were combined with O. compressus L. It demonstrated that degradation is likely to be reversed, thus giving to soil more physical support.

Chile holds ~50% of temperate forests in the Southern Hemisphere, thus constituting a genetic–ecological heritage. However, intense anthropogenic pressures have been inducing distinct forest structural-regeneration patterns. Accordingly, we evaluated 22 soil properties at 0–5 and 5–20 cm depths in two protected sites, with similar perturbation records but contrasting post-disturbance regeneration stages: long-term secondary forest (~50 y) (SEC_FORST) (dominated by Chusquea sp.-understory) and a short-term forest after disturbance (~5 y) (FAD_IST) within a Nothofagus spp. forest to determine the potential of these soils to promote nutrient availability, water cycling, soil organic carbon (SOC) sequestration (CO₂→SOC), and microbiome. Results detected 93 correlations (r ≥ 0.80); however, no significant differences (p < 0.05) in physical or chemical properties, except for infiltration velocity (+27.97%), penetration resistance (−23%), SOC (+5.64%), and % Al saturation (+5.64%) relative to SEC_FORST, and a consistent trend of suitable values 0–5 > 5–20 cm were estimated. The SOC→CO₂ capacity reached 4.2 ± 0.5 (FAD_IST) and 2.7 ± 0.2 Mg C y⁻¹ (SEC_FORST) and only microbial abundance shifts were observed. These findings provide relevant insights on belowground resilience, evidenced by similar ecosystem services provision capacities over time, which may be influenced progressively by opportunistic Chusquea sp.