Soil organic carbon sequestration potential explained by mineralogical and microbiological activity using spectral transfer functions.

The ability of soil to sequester carbon and reduce atmospheric CO2 concentrations is limited and depends on the soil minerals and their interaction with the microbiota. Microbial activities are closely associated with the types and amounts of soil organic matter (SOM) and clay minerals that have functional groups that interact with energy in Vis NIR-SWIR and Mid-IR wavelengths. The main objective of this research was to determine, based on these spectral ranges, the relation between mineralogical and organic compounds, as their sequestration and specialization in soils from Brazil. It was possible to map microbiological activity by spectral transfer functions and digital soil mapping reaching R2 from 0.77 to 0.85. Multiple regression equations were constructed to quantify enzymatic activity, microbial biomass carbon (MBC), particulate organic matter (POM), and resistant forms of carbon, and SOM associated with the mineral fraction (MAOM). All these properties were detected by specific bands obtained with the recursive feature elimination (RFE) algorithm, reaching correlations from 0.64 to 0.98 in specific ranges. The prediction model of the carbon sequestration potential was adjusted with microbiological and mineralogical variables from Vis-NIR-SWIR and the Mid-IR spectral range. A SARAR double autoregressive model was adjusted with r 0.61 and to a spatial error model (SEM) with r 0.7. The explanatory variables were associated with kaolinite, hematite, goethite, gibbsite, and the abundance of fungi, actinomycetes, vesico-arbuscular mycorrhizal fungi, enzymatic activity of beta-glucosidase, urease and phosphatase, and POM. Among the microbiological variables, the general abundance of fungi was the most important, in contrast to enzymatic activity that was the least important. The interaction between the different maps constructed and historical land use allowed the identification of areas that contribute to sequestering new carbon and could be the key to climate change mitigation strategies.

From waste to soil: Technosols made with construction and demolition waste as a nature-based solution for land reclamation.

Population growth has driven an increased demand for solid construction materials, leading to higher amounts of construction and demolition waste (C&DW). Efficient strategies to manage this waste include reduction, reuse, and recycling. Technosols-soils engineered from recycled waste-can potentially help with environmental challenges. However, there is a critical need to explore the potential of Technosols constructed with C&DW for land reclamation, through the growth of native vegetation. The objective of this study was to investigate this potential by studying two Brazilian native tree species (Guazuma ulmifolia and Piptadenia gonoacantha). Technosols were created using C&DW, with and without organic compost and a liquid biofertilizer. A soil health index (SHI) was applied to evaluate the soil quality regarding physical, chemical, and biological indicators of Technosols compared to a control soil (Ferralsol). The results showed that P. gonoacantha plants presented the same height and total biomass in all treatments, while G. ulmifolia plants exhibited greater height and total biomass when grown in Technosols. The enhanced plant development in the Technosols was primarily associated with higher cation exchangeable capacity and nutrients concentration in plant tissues. Technosols with added compost provided higher fertility and total organic carbon. Additionally, Technosols presented higher SHI (∼0.68) compared to control (∼0.38) for both studied species. Our experiment reveals that construction and demolition waste (C&DW) have significant potential to form healthy Technosols capable of supporting the growth of native Brazilian trees. This approach offers a promising alternative for addressing C&DW disposal challenges while serving as a nature-based solution for land reclamation.

Machine learning-based soil quality assessment for enhancing environmental monitoring in iron ore mining-impacted ecosystems.

In November 2015, a catastrophic rupture of the Fundão dam in Mariana (Brazil), resulted in extensive socio-economic and environmental repercussions that persist to this day. In response, several reforestation programs were initiated to remediate the impacted regions. However, accurately assessing soil health in these areas is a complex endeavor. This study employs machine learning techniques to predict soil quality indicators that effectively differentiate between the stages of recovery in these areas. For this, a comprehensive set of soil parameters, encompassing 3 biological, 16 chemical, and 3 physical parameters, were evaluated for samples exposed to mining tailings and those unaffected, totaling 81 and 6 samples, respectively, which were evaluated over 2 years. The most robust model was the decision tree with a restriction of fewer levels to simplify the tree structure. In this model, Cation Exchange Capacity (CEC), Microbial Biomass Carbon (MBC), Base Saturation (BS), and Effective Cation Exchange Capacity (eCEC) emerged as the most pivotal factors influencing model fitting. This model achieved an accuracy score of 92% during training and 93% during testing for determining stages of recovery. The model developed in this study has the potential to revolutionize the monitoring efforts conducted by regulatory agencies in these regions. By reducing the number of parameters that necessitate evaluation, this enhanced efficiency promises to expedite recovery monitoring, simultaneously enhancing cost-effectiveness while upholding the analytical rigor of assessments.

Clean and accurate soil quality monitoring in mining areas under environmental rehabilitation in the Eastern Brazilian Amazon.

Soil quality monitoring in mining rehabilitation areas is a crucial step to validate the effectiveness of the adopted recovery strategy, especially in critical areas for environmental conservation, such as the Brazilian Amazon. The use of portable X-ray fluorescence (pXRF) spectrometry allows a rapid quantification of several soil chemical elements, with low cost and without residue generation, being an alternative for clean and accurate environmental monitoring. Thus, this work aimed to assess soil quality in mining areas with different stages of environmental rehabilitation based on predictions of soil fertility properties through pXRF along with four machine learning algorithms (projection pursuit regression, PPR; support vector machine, SVM; cubist regression, CR; and random forest, RF) in the Eastern Brazilian Amazon. Sandstone and iron mines in different chronological stages of rehabilitation (initial, intermediate, and advanced) were evaluated, in addition to non-rehabilitated and native forest areas. A total of 81 soil samples (26 from sandstone mine and 55 from iron mine) were analyzed by both traditional wet-chemistry methods and pXRF. The available/exchangeable contents of K, Ca, B, Fe, and Al, in addition to H+Al, cation exchange capacity at pH = 7, Al saturation, soil organic matter, pH, sum of bases, base saturation, clay, and sand were accurately predicted (R2 > 0.70) using pXRF data, with emphasis on the prediction of Fe (R2 = 0.93), clay content (R2 = 0.81), H+Al (R2 = 0.81), and K+ (R2 = 0.85). The best predictive models were developed by RF and CR (86%) and when considering pXRF data + mining area + stage of rehabilitation (73%). The results highlight the potential of pXRF to accurately assess soil properties in environmental rehabilitation areas in the Amazon region (yet scarcely evaluated under this approach), promoting a more agile and cheaper preliminary diagnosis compared to traditional methods.

Ammonia volatization from conventional and stabilized fertilizers, agronomic aspects and microbiological attributes in a Brazilian coffee crop system.

We aimed to quantify the N losses through volatilization of the main conventional and stabilized N fertilizers applied in coffee plantations. Additionally, we also assessed microbiological attributes of the soil (microbial biomass carbon (MBC); microbial biomass nitrogen (MBN); microbial basal respiration (MBR); metabolic quotient (qCO2); urease, ß-glucosidase, acid phosphatase, and arylsulfatase activities) and agronomic aspects of the crop (N content in the leaves and beans, yield, and N exportation by the beans). Treatments consisted of the combination of three fertilizers (ammonium nitrate - AN, conventional urea - U, and urea with N- (n-butyl) thiophosphoric triamide (NBPT) - UNBPT, and five doses of N (0, 150, 275, 400, and 525 kg ha-1 year-1 of N), with four replicates, totalling 60 experimental plots. In the two crop seasons evaluated, daily and cumulative losses of N-NH3 from the split fertilizer applications were influenced by the N fertilizer technologies. The application of U resulted in losses of 22.0% and 22.8% for the doses of 150 and 400 kg ha-1 year-1 of N. This means that 66 and 182 kg ha-1 of N-NH3 were lost, respectively, at the end of six fertilizations with U. UNBPT reduced urease activity and N-NH3 losses compared to conventional urea, avoiding the volatilization of 15.9 and 24.3 kg ha-1 of N. As for AN, N-NH3 losses did not exceed 1% of the applied dose, regardless of the weather conditions during the fertilization. Urease activity was higher on days of maximum NH3 volatilization. There was an effect of the N sources (NS), soil sampling time (ST), and their interaction (NS × ST) on the MBN and arylsulfatase activity. The N sources also influenced the MBC and the qCO2. A substantial amount of N was removed from the system by the beans and husks of the harvested fruits. Our study showed that N fertilizer technologies are interesting options to reduce N-NH3 losses by volatilization, increase N retention in the soil, and improve microbiological attributes and the sustainability of coffee production systems.

Linking above and belowground carbon sequestration, soil organic matter properties, and soil health in Brazilian Atlantic Forest restoration.

Forest restoration mitigates climate change by removing CO2 and storing C in terrestrial ecosystems. However, incomplete information on C storage in restored tropical forests often fails to capture the ecosystem's holistic C dynamics. This study provides an integrated assessment of C storage in above to belowground subsystems, its consequences for greenhouse gas (GHG) fluxes, and the quantity, quality, and origin of soil organic matter (SOM) in restored Atlantic forests in Brazil. Relations between SOM properties and soil health indicators were also explored. We examined two restorations using tree planting ('active restoration'): an 8-year-old forest with green manure and native trees planted in two rounds, and a 15-year-old forest with native-planted trees in one round without green manure. Restorations were compared to reformed pasture and primary forest sites. We measured C storage in soil layers (0-10, 10-20, and 20-30 cm), litter, and plants. GHG emissions were assessed using CH4 and CO2 fluxes. SOM quantity was evaluated using C and N, quality using humification index (HLIFS), and origin using δ13C and δ15N. Nine soil health indicators were interrelated with SOM attributes. The primary forest presented the highest C stocks (107.7 Mg C ha-1), followed by 15- and 8-year-old restorations and pasture with 69.8, 55.5, and 41.8 Mg C ha-1, respectively. Soil C stocks from restorations and pasture were 20% lower than primary forest. However, 8- and 15-year-old restorations stored 12.3 and 28.3 Mg ha-1 more aboveground C than pasture. The younger forest had δ13C and δ15N values of 2.1 and 1.7‰, respectively, lower than the 15-year-old forest, indicating more C derived from C3 plants and biological N fixation. Both restorations and pasture had at least 34% higher HLIFS in deeper soil layers (10-30 cm) than primary forest, indicating a lack of labile SOM. Native and 15-year-old forests exhibited higher soil methane influx (141.1 and 61.9 µg m-2 h-1). Forests outperformed pasture in most soil health indicators, with 69% of their variance explained by SOM properties. However, SOM quantity and quality regeneration in both restorations approached the pristine forest state only in the top 10 cm layer, while deeper soil retained agricultural degradation legacies. In conclusion, active restoration of the Atlantic Forest is a superior approach compared to pasture reform for GHG mitigation. Nonetheless, the development of restoration techniques to facilitate labile C input into deeper soil layers (>10 cm) is needed to further improve soil multifunctionality and long-term C storage.

Biochar as a carbonaceous material to enhance soil quality in drylands ecosystems: A review.

Drylands are fragile environments that should be carefully managed to improve their quality and functions to achieve sustainable development. Their major problems involve low availability of nutrients and soil organic carbon content. Biochar effect on soil is a joint response of micro to nano sized biochar and soil characteristics. In this review, we attempt to carry out a critical analysis of biochar application to enhance dryland soil quality. Correlating the effects identified from its soil application, we explored the subjects that remains open in the literature. The relation of composition-structure-properties of biochar vary among pyrolysis parameters and biomass sources. Limitations in soil physical quality in drylands, such as low water-holding capacity, can be alleviated by applying biochar at a rate of 10 Mg ha-1 also resulting in beneficial effects on soil aggregation, improved soil porosity, and reduced bulk density. Biochar addition can contribute to the rehabilitation of saline soils, by releasing cations able to displaces sodium in the exchange complex. However, the recovery process of salt-affected soils might be accelerated by the association of biochar with another soil conditioners. This is a promising strategy especially considering the biochar alkalinity and variability in nutrients bioavailability to improve soil fertilization. Further, while higher biochar application rate (>20 Mg ha-1) might change soil C dynamics, a combination of biochar and nitrogen fertilizer can increase microbial biomass carbon in dryland systems. Other aspect of biochar soil application is the economic viability of scale-up production, which is mainly associate to pyrolysis process being biochar production the costliest stage. Nevertheless, the supplying of feedstock might also represent a great input on biochar final costs. Therefore, biochar-based technology is a big opportunity to improve fragile environments such as drylands, integrating sustainable technologies with regional development. Considering the specificity of application area, it might be a model of sustainable agricultural practices protecting the environment in a bioeconomic perspective.

The role of land use, management, and microbial diversity depletion on glyphosate biodegradation in tropical soils.

Land use and management changes affect the composition and diversity of soil bacteria and fungi, which in turn may alter soil health and the provision of key ecological functions, such as pesticide degradation and soil detoxification. However, the extent to which these changes affect such services is still poorly understood in tropical agroecosystems. Our main goal was to evaluate how land-use (tilled versus no-tilled soil), soil management (N-fertilization), and microbial diversity depletion [tenfold (D1 = 10-1) and thousandfold (D3 = 10-3) dilutions] impacted soil enzyme activities (ß-glycosidase and acid phosphatase) involved in nutrient cycles and glyphosate mineralization. Soils were collected from a long-term experimental area (35 years) and compared to its native forest soil (NF). Glyphosate was selected due to its intensive use in agriculture worldwide and in the study area, as well as its recalcitrance in the environment by forming inner sphere complexes. Bacterial communities played a more important role than the fungi in glyphosate degradation. For this function, the role of microbial diversity was more critical than land use and soil management. Our study also revealed that conservation tillage systems, such as no-tillage, regardless of nitrogen fertilizer use, mitigates the negative effects of microbial diversity depletion, being more efficient and resilient regarding glyphosate degradation than conventional tillage systems. No-tilled soils also presented much higher ß-glycosidase and acid phosphatase activities as well as higher bacterial diversity indexes than those under conventional tillage. Consequently, conservation tillage is a key component for sustaining soil health and its functionality, providing critical ecosystem functions, such as soil detoxification in tropical agroecosystems.

Evaluation of some microbiological attributes of the soil in two different management systems / Avaliação de atributos microbiológicos do solo em dois diferentes sistemas de manejo

The maintenance of organic matter in tropical soils and the use of soil quality indicators that can express its changes in sustainable agricultural systems is very important for monitoring the health of these ecosystems with high productivity and longevity. The aim of this experiment was to evaluate, through enzymatic responses of microbiological activity, variations resulting from different cultivation systems under sandy soil conditions in western of São Paulo State. In this purpose, the measurement of the parameters microbial biomass carbon (MBC), microbial biomass nitrogen (NBM), dehydrogenase (DNSE), basal respiration (BR) and the metabolic quotient (qCO2) in two culture systems characterized by being a succession of annual crops with soybean/corn (annual crops) and the other under perennial pasture of the genus Urochloa (pasture), respectively. It was verified that the two systems presented different behaviors related to the evaluated microbiological attributes, showing higher values in the evaluated microbial attributes in the area where Urochloa grass was cultivated.

A manutenção da matéria orgânica em solos tropicais e o uso de indicadores de qualidade do solo que possam expressar suas alterações em sistemas agrícolas sustentáveis é de grande importância para o monitoramento da saúde desses ecossistemas com alta produtividade e longevidade. Buscou-se neste experimento avaliar dois diferentes sistemas de cultivo sob condições de solos arenosos do oeste paulista, respostas diferentes nas atividades microbiológicas, decorrentes destes manejos. Neste sentido, procedeu-se a mensuração dos parâmetros carbono da biomassa microbiana (CBM), nitrogênio da biomassa microbiana (NBM), desidrogenase (DNASE), respiração basal (RB) e o quociente metabólico (qCO2), em dois sistemas de cultivo agrícola caracterizados por serem sucessão de culturas anuais com soja/milho (cultivos anuais) e o outro sob pastagem perene do gênero Urochloa (pastagens), respectivamente. Verificou-se que os dois sistemas apresentaram comportamentos diferentes relacionados aos atributos microbiológicos avaliados, apresentando maiores valores dos atributos biológicos na área onde havia o cultivo da gramínea do gênero Urochloa.

Arbuscular Mycorrhizal Fungi and Soil Quality Indicators in Eucalyptus genotypes With Different Drought Tolerance Levels.

Silviculture has great importance worldwide, and the use of Eucalyptus species, which account for 75% of the local planted forest in Brazil, is one of the factors that contributes to the success of this activity in the country. Despite its adaptability, the yield of Eucalyptus is often affected by climate change, particularly water deficiency. Plants have developed strategies to mitigate water stress, for example, through their association with mycorrhizal fungi. The genus Eucalyptus, particularly in the plant domain, establishes symbioses with arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (ECMF). The influence of Eucalyptus species on AMF and soil quality indicators is not well understood. Our aim was to conduct a preliminary evaluation of the various responses of soil AMF communities and soil nutrient dynamics in the presence of Eucalyptus species with different degrees of drought tolerance. A field experiment was established containing six Eucalyptus species, E. brassiana, E. camaldulensis, E. citriodora, E. cloeziana, E. grandis, and E. urophylla, all of which were planted in large plots. Soil and root samples were taken when the plants were 1.7 and 2.2 years old. We found that Eucalyptus species with low (E. grandis and E. urophylla) and intermediate drought tolerance (E. citriodora and E. cloeziana) showed stronger correlations with the AMF community than Eucalyptus species with high drought tolerance (E. brassiana and E. camaldulensis). Differences were also found between Eucalyptus species for AMF spore numbers and root colonization percentages, which was most evident for E. urophylla. The microbiological attributes found to be most responsive to Eucalyptus species were soil enzyme activities, AMF spore numbers, root colonization percentages, and fungal abundance. Soil organic carbon, phosphorus, potassium, zinc, copper, and iron were the main chemical drivers related to the soil AMF community structure in the presence of E. brassiana.

Beneficial services of Glomalin and Arbuscular Mycorrhizal fungi in degraded soils in Brazil

Reducing soil degradation and its impacts on the environment have been one of the main challenges of the 21st century, exacerbated by a direct link between increases in the human population and soil degradation that raises current and future food security concerns. Despite this, experiences worldwide reveal that degraded land restoration projects have either achieved little success or failed. Thus, understanding the underlying causes and devising appropriate restoration mechanisms is crucial. Soil amelioration using beneficial microorganisms, particularly arbuscular mycorrhizal fungi (AMF), is essential and pragmatic. Glomalin, a type of glycoprotein produced by arbuscular mycorrhizal fungi in the phylum Glomeromycota, contributes to the mitigation of soil degradation. Moreover, AMF and glomalin are highly correlated with other soil physico-chemical parameters and are sensitive to changes in the environment. As a result of this, they have been recommended for monitoring the recovery of degraded soil or stages of soil degradation. In this review, we discuss the role of AMF and glomalin in the restoration of degraded soils, including improvements to the soil structure and soil organic matter (SOM), microbial activity, reduction of fertility loss, bioremediation, and mitigation of the effects of drought and saline stress. We highlight the research gaps and discuss the prospects. This knowledge will improve our understanding of the ecological conduct of glomalin and AMF, stimulate future research, and be useful to sustainable restoration of degraded lands. Furthermore, we discussed the challenges and obstacles in the legislation and future perspectives on the production of inoculants based on AMF in Brazil.

Enzyme activities in a sandy soil of Western Bahia under cotton production systems: short-term effects, temporal variability, and the FERTBIO sample concept.

Enzyme activities (EAs) and the FERTBIO sample concept have been increasingly adopted as a novel approach to estimate the soil quality in Brazil. However, the performance of this strategy in sandy soils of the Cerrado biome remains unclear. During 2 years, in a Cerrado's sandy soil, the short-term effects of ten different cropping systems (conventional tillage or no-tillage associated with monoculture, rotations, and/or successions) on the activities of ß-glucosidase, acid phosphatase, and arylsulfatase were studied. Issues related to annual variability and the feasibility of using the FERTBIO sample concept for soil enzymes activities were also evaluated. Soil samples were collected at three different depths (0-10 cm, 10-20 cm, and 20-40 cm) in March 2017 and February 2018. Five years since the beginning of the experiment, the presence of cover crops and no-till promoted improvements in EAs evidencing the importance of regenerative management practices for the sustainability of agroecosystems in sandy soils. Regardless of the cropping systems and depths evaluated, soil organic carbon and EAs showed low temporal variation during the 2 years of monitoring. Our results also showed that it is possible to use the FERTBIO sample concept for the Quartzipsament soils of Western Bahia, Brazil.

Validation of soil quality index in soil using bioindicator plant / Validação do índice da qualidade do solo com planta bioindicadora

Soils provide a broad set of vital ecosystem services and sustains the production of food and fibers, balancing the ecosystem. Thus, from the perspective of soil quality, it is defined as an ability to balance within the ecosystem to sustain biological productivity, promoting the health of plants and animals, being evaluated by traditional indicators as physical, chemical and biological indicators, so the present work aims to estimate the soil quality index using multivariate models using soil biological attributes and validation with growth variables of the bioindicator plant. The study was developed in the agricultural area in P. Prudente, SP, the points collected were georeferenced, collections in depth of 0 -20 cm, microbiological analysis, microbial carbon and nitrogen biomass, dehydrogenase, respiration and microbial coefficient, having a bioindicator plant curly lettuce (Lucy Brown) as a validator of the soil. The results were discovered using the PCA model for the identification of autos vectors and autos values, grouping and identifying their collinearities, linear regression, r-pearson validation and cluster heuristic analysis. The microbial attributes and the bioindicator plant discriminated the agricultural areas evaluated with establishment and validation of SQI. The metabolic coefficient and N of the microbial biomass dissipation of the highest covariance values by multivariate analysis. The reforestation area with native species (SQI0.782%) and the livestock crop integration system (SQI0.765%) were evaluated as areas with better soil quality.

O solo fornece o conjunto de serviços ambientais vitaise dinâmico que condiciona e sustenta a produção de alimentos e fibras, balanceando o ecossistema, dessa forma, sob a ótica da qualidade do solo é definida como a capacidade de se equilibrar dentro do ecossistema para sustentar a produtividade biológica, promovendo a saúde das plantas e animais, sendo avaliada pelos indicadores tradicionais como indicadores físicos, químicos e biológicos, assim o presente trabalho tem como objetivo estimar índice qualidade do solo com uso de modelos multivariados utilizando-se de atributos biológicos do solo e validação com variáveis de crescimento da planta bioindicadora. O estudo foi desenvolvido na área agrícola da universidade do Oeste Paulista, campus II, os pontos coletados foram georreferenciados, coletatos em profundidade de 0 –20 cm, realizado as análises microbiológicas, biomassa microbiana do carbono e nitrogênio, desidrogenase, respiração e coeficiente microbiano, tendo a planta bioindicadora alface crespa (Lucy Brown) como validador do solo. Os resultados foram submetidos ao modelo de PCA para a identificação dos autos vetores e autos valores agrupando e identificando suas colinearidades, regressão linear, validação r-pearson e análise heurística de cluster. Os atributos microbianos e a planta bioindicadora discriminaram as áreas agrícolas avaliadas com atribuição e validação de SQI. O coeficiente metabólico e N da biomassa microbiana apresentaram os maiores valores de covariância pela análise multivariada. A área de reflorestamentocom espécies nativas (SQI0,782%) e o sistema de integração lavoura pecuária (SQI0,765%) foram consideradas as áreas com melhor qualidade de solo.

Validation of soil quality index in soil using bioindicator plant / Validação do índice da qualidade do solo com planta bioindicadora

Soils provide a broad set of vital ecosystem services and sustains the production of food and fibers, balancing the ecosystem. Thus, from the perspective of soil quality, it is defined as an ability to balance within the ecosystem to sustain biological productivity, promoting the health of plants and animals, being evaluated by traditional indicators as physical, chemical and biological indicators, so the present work aims to estimate the soil quality index using multivariate models using soil biological attributes and validation with growth variables of the bioindicator plant. The study was developed in the agricultural area in P. Prudente, SP, the points collected were georeferenced, collections in depth of 0 -20 cm, microbiological analysis, microbial carbon and nitrogen biomass, dehydrogenase, respiration and microbial coefficient, having a bioindicator plant curly lettuce (Lucy Brown) as a validator of the soil. The results were discovered using the PCA model for the identification of autos vectors and autos values, grouping and identifying their collinearities, linear regression, r-pearson validation and cluster heuristic analysis. The microbial attributes and the bioindicator plant discriminated the agricultural areas evaluated with establishment and validation of SQI. The metabolic coefficient and N of the microbial biomass dissipation of the highest covariance values by multivariate analysis. The reforestation area with native species (SQI0.782%) and the livestock crop integration system (SQI0.765%) were evaluated as areas with better soil quality.(AU)

O solo fornece o conjunto de serviços ambientais vitaise dinâmico que condiciona e sustenta a produção de alimentos e fibras, balanceando o ecossistema, dessa forma, sob a ótica da qualidade do solo é definida como a capacidade de se equilibrar dentro do ecossistema para sustentar a produtividade biológica, promovendo a saúde das plantas e animais, sendo avaliada pelos indicadores tradicionais como indicadores físicos, químicos e biológicos, assim o presente trabalho tem como objetivo estimar índice qualidade do solo com uso de modelos multivariados utilizando-se de atributos biológicos do solo e validação com variáveis de crescimento da planta bioindicadora. O estudo foi desenvolvido na área agrícola da universidade do Oeste Paulista, campus II, os pontos coletados foram georreferenciados, coletatos em profundidade de 0 –20 cm, realizado as análises microbiológicas, biomassa microbiana do carbono e nitrogênio, desidrogenase, respiração e coeficiente microbiano, tendo a planta bioindicadora alface crespa (Lucy Brown) como validador do solo. Os resultados foram submetidos ao modelo de PCA para a identificação dos autos vetores e autos valores agrupando e identificando suas colinearidades, regressão linear, validação r-pearson e análise heurística de cluster. Os atributos microbianos e a planta bioindicadora discriminaram as áreas agrícolas avaliadas com atribuição e validação de SQI. O coeficiente metabólico e N da biomassa microbiana apresentaram os maiores valores de covariância pela análise multivariada. A área de reflorestamentocom espécies nativas (SQI0,782%) e o sistema de integração lavoura pecuária (SQI0,765%) foram consideradas as áreas com melhor qualidade de solo.(AU)

Soil microbial community, enzyme activity, C and N stocks and soil aggregation as affected by land use and soil depth in a tropical climate region of Brazil.

The impact of agricultural land-use on soil microbial community composition and enzyme activity has not been extensively investigated in Ultisols. We investigated soil health parameters by analyzing phospholipid fatty acids (PLFAs), extracellular enzyme activity, C and N stocks, and soil structure. Four land uses were established in a tropical climate region of Brazil: native Cerrado (savanna), monoculture pasture [Urochloa brizantha (Hochst. Ex A. Rich.) R. Webster 'Marandu'], an integrated crop-livestock system (ICLS), and maize (Zea mays)-fallow in a no-tillage system. Soil microbial biomass was 40% higher in the native Cerrado than in the monoculture pasture, ICLS, and no-tillage maize. Soil organic carbon was positively correlated with microbial community composition (MB; gram-; AC; AMF; Fungi; F: B ratio) and enzyme activity (bG, AP, NAG). Large macroaggregates were positively correlated with bG, AP, and AMF. In summary, the native Cerrado had a higher level of carbon at the soil surface and greater soil structure with increased microbial biomass, gram+ bacteria, AMF, fungi, and F:B ratio in a tropical region of Brazil. However, bG and AP enzyme activities were lower in the ICLS and no-till maize at the soil surface (0-5 cm) compared to the native Cerrado. The conversion of native Cerrado to agricultural systems shifted the soil microbial community composition, enzyme activity, C and N, and soil structure of this sandy soil of the Brazilian Cerrado.

Improved Pastures Support Early Indicators of Soil Restoration in Low-input Agroecosystems of Nicaragua.

Pasture degradation hinders livestock production and ecosystem services that support rural smallholder communities throughout Latin America. Silvopastoral systems, with improved pasture cultivars (especially Brachiaria spp.) and multipurpose trees, offer a promising strategy to restore soils and improve livelihoods in the region. However, studies evaluating the impact of such systems on pasture productivity and soil health under realistic smallholder constraints are lacking. We evaluated the impact of improved pasture grass and tree establishment on a suite of soil health indicators in actively grazed, low-input, farmer-managed silvopastoral systems. In August 2013, paired pasture treatments (improved grass with trees vs. traditional pastures) were established on nine farms with similar land-use histories near Matagalpa, Nicaragua. On each farm, one treatment was left as traditional pasture with naturalized grass (Hyparrhenia rufa), while the adjacent treatment was sown with the improved grass (Brachiaria brizantha cv. Marandu) and planted with tree saplings without fertilizer. In August 2015, we measured standing biomass and a suite of chemical, biological, and physical soil health variables. Improved silvopastoral systems with B. brizantha produced more standing grass biomass and supported higher levels of earthworm populations and permanganate oxidizable carbon (POXC) compared to the traditional control. Correlations suggest that earthworms and POXC were associated with incipient improvements to soil aggregate stability and water holding capacity. We report measurable improvements to soil health just two years following the establishment of improved pasture systems under common smallholder management practices and suggest that these systems, even with minimal fertility inputs, have the potential to enhance regional sustainability.