Brasília, v. 19, n. 3, p. 259-283, 2024

https://doi.org/10.33240/rba.v19i3.52163

Como citar: MANGIONE, Stella Maris et al. Caracterización de la calidad edáfica en agroecosistemas gestionados por familias campesinas de Pirané, Formosa, Argentina. Revista Brasileira de Agroecologia, v. 19, n. 3, p. 259-283, 2024.

Characterization of the edaphic quality in agroecosystems managed by peasant families of Pirané, Formosa, Argentina

Caraterização da qualidade edáfica em agroecossistemas gerenciados por famílias de camponeses de Pirané, Formosa, Argentina

Caracterización de la calidad edáfica en agroecosistemas gestionados por familias campesinas de Pirané, Formosa, Argentina

Stella Maris Mangione1; Dennis José Salazar Centeno2; Nora Trejo3; Liliana Rosa Galián4

1Professor of Free Chair of Family Agriculture and Food Sovereignty. Faculty of Agrarian Sciences, National University of Lomas of Zamora, Buenos Aires. Degree in Biology for the National University of La Plata. Coordinator of the Agroecological Centre ASHPA, President Peron, Buenos Aires, Argentina. ORCID: https://orcid.org/0000-0003-3315-8392. e-mail ceashpa@gmail.com

2Retired professor of the National Agricultural University, Managua, Nicaragua. Doctor of agriculturarum, for University of Leipzig (Leipziger Universität), Leipzig, Germany. ORCID: https://orcid.org/0000-0003-3281-2348. e-mail dennis.salazar1962@gmail.com

3Professor Chair of Microbiology. Faculty of Agrarian Sciences, National University of Lomas of Zamora. Buenos Aires. Agricultural engineer for National University of Lomas of  Zamora. Buenos Aires, Argentina.  ORCID: https://orcid.org/0000-0003-2045-1186. e-mail microbiologia@agrarias.unlz.edu.ar

4 Professor Chair of Microbiology. Faculty of Agrarian Sciences, National University of Lomas of Zamora. Buenos Aires. Agricultural engineer for National University of Lomas of  Zamora. Buenos Aires, Argentina. ORCID:https://orcid.org/0000-0001-5889-0892.e-mail microbiologia@agrarias.unlz.edu.ar

Submited on: 03 jan 2024 – Accepted on: 18 jun 2024

Abstract

Soil quality can be inherited, related to formation processes, and dynamic, especially due to those introduced by human activity. The objective of this research was to characterize the edaphic quality of four peasant agroecosystems through physical, chemical, biological indicators, and anthropogenic factors. This was proposed as a baseline for monitoring soil quality and for the implementation of technologies and practices for the promotion of the agroecological paradigm. The methodological perspective adopted was mixed. It was determined that the strongly acidic pH in the soil of AAA is the limiting chemical factor, while moderate salinity in TAG and TAD restricts plant nutrition. In the four agroecosystems, Colony Forming Units per gram of soil were quantified. These belonged to diazotrophic microorganisms, NH4+ and NO₂- oxidizers, phosphorus solubilizers, cellulolytic fungi and total fungi. These populations are highly susceptible to edaphoclimatic conditions and anthropogenic influences, yet they play a pivotal role in natural biofertilization, natural biostimulation, biological control and natural bioremediation, which collectively facilitate the suppression of detrimental effects on these soils.

Keywords: Agroecology, Biofertilization, Bioremediation, Soil health, Soil microorganisms.

Resumo

A qualidade do solo pode ser herdada, em relação aos processos de formação e dinâmica, especialmente associados à atividade humana. O objetivo desta pesquisa foi caracterizar a qualidade do solo de quatro agroecossistemas camponeses por meio de indicadores físicos, químicos, biológicos e fatores antropogênicos. Isso foi proposto como uma linha de base para o monitoramento da qualidade do solo e para a implementação de tecnologias e práticas na promoção do paradigma agroecológico. A perspectiva metodológica foi mista. Foi determinado que o pH fortemente ácido no solo em AAA é um fator químico limitante, enquanto a salinidade moderada no ATH e no ATD restringe a nutrição das plantas. Nos quatro agroecossistemas foram quantificadas as Unidades Formadoras de Colônias por grama de solo, pertencentes a microrganismos diazotróficos, oxidantes de NH4+ e NO₂-, solubilizadores de fósforo, fungos celulolíticos e fungos totais. Estas populações são muito sensíveis às condições edafoclimáticas e aos efeitos antropogênicos, mas contribuem para a biofertilização natural, para a bioestimulação natural, para o controle biológico natural e para a biorremediação natural, que, em conjunto, facilitam a supressão de efeitos prejudiciais nesses solos.

Palavras-chave: Agroecología, Biofertilização, Biorremediação, Microorganismos do solo, Saúde do solo.

Resumen

La calidad del suelo puede ser heredada, en relación con los procesos de formación y dinámica, especialmente debido a aquellos introducidos por la actividad humana. El objetivo de esta investigación consistió en caracterizar la calidad edáfica de cuatro agroecosistemas campesinos a través de indicadores físicos, químicos, biológicos y factores antropogénicos. Esto se planteó como línea de base para el monitoreo de la calidad del suelo y para la implementación de tecnologías y prácticas que promuevan el paradigma agroecológico. La perspectiva metodológica adoptada fue mixta. Se determinó que el pH fuertemente ácido en el suelo de AAA es el factor químico limitante, mientras que la salinidad moderada en ATH y ATD restringe la nutrición vegetal. En los cuatro agroecosistemas, se cuantificaron las Unidades Formadoras de Colonia por gramo de suelo, pertenecientes a microorganismos diazótrofos, oxidante de NH4+ y NO₂-, solubilizadores de fósforo, hongos celulolíticos y hongos totales. Estas poblaciones son muy sensibles a las condiciones edafoclimáticas y a los efectos antropogénicos, pero contribuyen a la biofertilización natural, la bioestimulación natural, el control biológico natural y la biorremediación natural, que en conjunto, facilitan la supresión de efectos perjudiciales en estos suelos.

Palabras claves: Agroecología, Biofertilización, Biorremediación, Microorganismos edáficos, Salud del suelo.  

INTRODUCTION       

The soil is considered an “independent natural body with its own morphology, product of the joint action of climate, vegetation and living beings on a rock, during a certain period of time” (Ortiz-Silla, 2015, p. 53). Cantú et al. (2007) reveal that, until 1992, at the United Nations Conference on Environment and Development (UNCED) emphasized on the urgency of developing and applying methodologies to “determine the state of the environment and monitor changes that have occurred at the local, national, regional and global levels” (p. 173). These same authors highlight that the application of Chapter 40 of Agenda 21 led to the development and application of different indicators and indices, among which those related to determining soil quality. The concept of soil quality was defined, for the first time, by the Soil Science Society of America (Karlen et al., 1997), which is evaluated with indicators. An indicator “is a variable that summarizes or simplifies relevant information, making a phenomenon or condition of interest perceptible and that quantifies, measures and communicates, in an understandable way, relevant information” (Cantu et al., 2007, p. 174). In this sense, quantitative and qualitative indicators have been proposed for the evaluation of soil quality (Doran and Parkin, 1997; García; Ramirez; Sánchez, 2012; Grupo Operativo Leñosost, 2020).

Both soil quality and dynamic can be inherited. The first refers to the soil formation processes (long-term changes) and the second to the use and management of the soil by man (short and medium-term changes), which originated the concept of soil health, (Ortiz-Silla, 2015), which implies that the soil compromises its health or quality due to anthropogenic influence. The quality or health of the soil is evaluated by physical, chemical and biological indicators and their interactions; therefore, it is necessary to analyze them together (Afanador-Barajas et al., 2020). However, only in recent times has it been suggested that soils contain an active biological component, which contributes to their sustainability (Moreira; Huising; Bignell, 2012) and allows it to be dimensioned as a 'living system' (Sánchez de Praguer et al., 2007) vision that, “contributes to the health of the planet, the quality of food and the permanence of the soil over time” (Sánchez de Praguer et al., 2012, p. 26). In response to this situation, the Initiative for the Conservation and Sustainable Use of Soil Biodiversity emerged, which emphasized the importance of long-term soil diversity evaluation and management. (FAO, 2020).

The World Soil Charter states that healthy soils are a basic prerequisite for meeting diverse needs for food, biomass (energy), fibre, fodder and other products, and for ensuring the provision of essential ecosystem services in all regions of the world (FAO, 2015). Nine planetary boundaries affect the security of the biosphere, and, therefore, the sustainability of agroecosystems and ecosystem services (Rockström et al., 2009), of which five are related to food production, which are: climate change, land use change, biochemical fluxes of nitrogen (N) and phosphorus (P), the integrity of the biosphere and freshwater use (Salazar-Centeno; Jürgen; Marroquín, 2023). These realities require characterizing the edaphic quality of the agroecosystems managed by peasant families and providing guidelines for the promotion the agroecology paradigm. That is, to guarantee essential ecosystem services for maintaining the quality of life of human and the conservation of biodiversity (Kibblewhite; Ritz; Swift, 2007).

So far, in the province of Formosa, Argentina, the soil quality of peasant agroecosystems has not been characterized, which integrates physical, chemical, microbiological indicators, their interactions and the anthropogenic effect. For most biological indicators, there is little evidence available that directly relates the value of the indicator to productivity or the risk of negative environmental impact (Videla and Picone, 2017). In the Pampean region, studies have been conducted under different climatic conditions and agronomic management of soil quality with biological and/or physical, and/or chemical indicators (Baridón, 2015; De Luca; Salazar-Martínez; Pérez, 2018; Faggioli and Symanczik, 2018; Fernández et al., 2018).

The objective of this work is to characterize the edaphic quality of peasant agroecosystems through a diagnosis using physical, chemical, and microbiological indicators and the anthropogenic influence in four agroecosystems, in the municipality of Villa Dos Trece, Pirané Sur, Formosa, Argentina.

MATERIALS AND METHODS

Location of the agroecosystems and study period

The study was conducted in four agroecosystems (one agroecological, one conventional and two in transition) during the period from August, 2018 to September, 2019 (Table 1). Agroecosystems are managed by peasant families that make up agricultural colonies, from the Jurisdiction of Villa Dos Trece – Pirané, located in lot 20 and Colonia km 210, province of Formosa, Argentina (Figure 1).

Figure 1. Location of agroecosystems, Jurisdiction Villa Dos Trece, Pirané, Formosa, Argentina.

Source: Platform Mapcreator, QGis 2.8.1 y Google Earth Pro 2023.

 

Pirané is located in the humid Chaco Ecoregion (Burkart et al., 1999), and is divided into two productive zones, Pirané Sur and Pirané Norte. Pirané Sur has a total area of 3,136 km2 and includes the towns of Palo Santo, El Colorado, Mayor Edmundo Villafañe and Villa Dos Trece (Schaller, 2013).

The climate is subtropical-subhumid, with rainfall between 600 and 1,200 mm annually. According to the physiographic map, it comprises the landscape unit called the Old Delta of the Bermejo River, which includes a plain of alluvial origin characterized by the alternation of albardons, floodable interfluves, plains dissected by paleochannels and paleovalleys with rambling channels. The sediments of this sector are mostly colloidal, composed of clay minerals and organic matter in different stages of degradation (Schulz; Rodríguez; Moretti, 2017).

Approach, scope, methodological design and selection criteria of agroecosystems

The methodological perspective adopted was mixed, with a quantitative approach, complemented by a qualitative approach that corresponds to a multiple case study (Yin, 2003). The scope of the quantitative approach is descriptive and correlational, with a non-experimental transectional design. The qualitative methodological perspective consisted of the combination of symbolic interactionism, whose method and technique were the individual semi-structured interview and the ethnographic approach, whose method and technique were participant observation, which contributed to the characterization of subsystems and management of agroecosystems, which was supported by a documentary analysis. The selection criteria for the four agroecosystems were based on those formulated by Mangione and Salazar-Centeno (2021). The agroecosystems were (Table 1): Agroecological Agroecosystem the Grove (AAG); Conventional Agroecosystem Don Enrique (CAD), Transition Agroecosystem Organic Garden (TAG); Transition Agroecosystem Mrs. Lola (TAM).

Table 1. Main characteristics of the studied agroecosystems (2018-2019).

Source: Mangione and Salazar-Centeno, 2021.

Soil sampling for physical and chemical indicators

Soil sampling in the subsystems with horticultural production was random. Homogenized samples were obtained for each agroecosystem at a depth of 0 to 15 cm (Mendoza-Corrales and Espinoza, 2017). Physical and chemical soil parameters were: texture by the Bouyoucos method; pH (paste), potentiometric method; electrical conductivity in dS m-1 (EC) by conductimetry of the saturation extract (25ºC); percentage of total Nitrogen (tN%) by the Micro-Kjeldahl method; percentage of organic carbon (OC%) and percentage of organic matter (OM%) with the Walkley-Armstrong Black wet oxidation method; Nitrogen from nitrates (NO3-) in ppm by phenol-disulfonic acid colorimetry; available elemental Phosphorus in ppm (P) by the modified Bray-Kurtz method; Cation exchange capacity (CEC) method Washing of bases with 1N ammonium acetate pH 7.0 and evaluation of the retained nitrogen by the Kjeldahl method.

The determination of diazotrophic bacteria was performed by the method of serial dilutions in triplicate (Döbereiner and Day, 1976). It was incubated at 30° C for 48 to 72 hours. The CFU g-1 of soil from ammonium-oxidizing bacteria (NH4+) and nitrite- oxidizing (NO3-) were obtained by sowing in specific broths. They were incubated for 30 days under continuous agitation in an ORBITAL SHEKER at 300 r.p.m. and were quantified using the most probable number technique (Alef and Nannipieri, 1995). The CFU g-1 of soil of phosphorus (P) solubilizing microorganisms were performed in triplicate in Petri dishes, with solid NBRIP medium (Nautiyal, 1999). The CFU g-1 of cellulolytic fungi soil was performed in broth with the addition of cellulose paper (Alef and Nannipieri, 1995), using the most probable number technique. It was incubated for 30 days under continuous agitation.

From an agronomic perspective, the pH of the AAG is strongly acidic (5.24) and is reflected in lower values of the CEC (14.7 meq. in 100 g of soil) and total nitrogen (0.22 %) so it is very likely that the number of cations in the exchange complex (organic and inorganic) with the soil solution is lower (Table 2). The pH of the CAD soil (7.37) typifies it as a very slightly alkaline soil because it exceeds the threshold of seven by 0.37 (Table 2). In these two agroecosystems, the salinity of their soils does not restrict the plant growth because the EC is 0.93 dS m-1 and 0.7 dS m-1 (Table 2). The soil of the TAG and TAM is moderately acidic and slightly acidic with a pH of 5.96 and 6.40, respectively (Table 2). These values are located in the optimal range of this chemical indicator so that nutrients are more available for productive plant biodiversity. The salinity of these soils is moderate with 2.62 dS m-1 y 2.67 dS m-1 (Table 2), which can restrict the growth and yield of cultivated plants.

Andrade-Ochoa et al. (2015) state that the greatest participation of microorganisms occurs in the biogeochemical nitrogen cycle (BNC). Diazotrophic bacteria (DB) reduce or fix atmospheric bimolecular nitrogen (N2) to make it assimilable by the productive plants and auxiliary biodiversity (Assimilation) in the form of the ammonium cation (NH4+) and perform the enzymatic digestion of NH4+, which degrades it to amino compounds (proteases, peptones and amino acids), a process known as ammonification or mineralization (Gaviria-Giraldo et al., 2018; Innovatione AgroFood Design, 2019). López (2022) found that DB adapted well to agroecological and conventional management of agroforestry systems with coffee, which was reflected in the highest values of CFU g-1 of soil. Beltrán-Pineda and Lizarazo-Forero (2013) state that the bacteria involved in atmospheric N2 reduction reached higher populations because the physicochemical conditions of undisturbed and burned soils favor their abundance. This high plasticity of the DB to adapt to different agroecosystem management environments is the reason why they reached the largest populations in the four agroecosystems (Table 4). Clavijo et al. (2012) found that native DB correlates with organic matter, phosphorus (P) and soil pH, an association that was not always confirmed in this characterization of edaphic quality (Tables 2 and 3).

The results of the CFU g-1 of soil of diazotrophic bacteria and NH4+ oxidizing bacteria shows that the edaphoclimatic conditions and the management carried out by peasant families in each agroecosystem exert a very marked influence on the reproduction capacity of these bacteria. Therefore, it is to be expected that the amount of N2 fixed and that of the NH4+ cation oxidation in the soil is very dissimilar in each agroecosystem. This deduction is based on the highest coefficients of variation (140 % and 164 %) with respect to the general average of each functional group (Table 4), so it is more likely that the biological fixation of atmospheric N2 is less intense in the TAG soil, possibly due to a lower organic matter content (OM %) (Table 2). The OM % content of the TAG soil is classified as moderately supplied (2.9 %); while this chemical edaphic parameter in the soils of AAG, CAD and TAM is characterized as well supplied (3.2 %), very well supplied (4.6 %) and well supplied (4 %), respectively (Table 2). This influence of soil-climatic conditions and the management carried out by peasant families, in each agroecosystem, on the reproductive capacity of NO₂- anion oxidizing bacteria is minor, so the oxidation of NO2- anion and NO3- anion are expected to be very similar.

The agroecological management of the TAG soil must encourage an increase in the percentage of its OM to favor the increase in CFU g-1 of soil of free-living diazotrophic microorganisms, which will be reflected in a lower dependence on synthetic nitrogenous and phosphorous fertilizers, reduced production costs and less environmental damage by mitigating the planetary limit related to the biochemical fluxes of N and P, which  have surpassed the area of uncertainty or increasing risk (Rockström et al., 2009). On the contrary, the greatest number of CFU g-1 of soil of this functional group in the AAG, the CAD and the TAM favors a more dynamic enzymatic activity of the diazotrophic bacteria with greater metabolic activity, which mainly promotes ecosystem services of regulation and support so that productive plant biodiversity and auxiliary express better growth and development through better nitrogen nutrition; greater resistance to the onslaught of pests and diseases, and consequently a better ecosystem supply service (Food, medicines, fibers, wood, energy, biomass). López (2022) concludes that the functional roles of the genera of edaphic microorganisms are more related to supporting, regulating and cultural ecosystem services; and indirectly to the ecosystem supply service since the biomass that is characterized as yield (Food, fiber, wood, energy or firewood) is the result of good growth and development of the producers (plants), in which natural biofertilization, the natural biostimulation of vegetables and natural biological control agents for pests and pathogens intervene.

The study of microbial processes of nitrification and denitrification are essential to promote the productivity of agroecosystems and to care for the environment (water and air), whose purpose must maintain the balance of the fundamental elements for life (Turrini; Sbrana; Giovannetti, 2015).

In the TAM and AAG soil, NH4+oxidation is more likely to cause greater availability of the NO2- anion, which is absorbed by the productive plant and auxiliary biodiversity or oxidized by other bacteria. Conversely, in both agroecosystems, there may be greater NO2- leaching because the silt loam textural class soils (Table 3) are moderately permeable.

Functional groups of edaphic microbes that participate in the biogeochemical phosphorus cycle

Biogeochemical processes associated with the release of P into plant-available forms include solubilization of inorganic P and mineralization of organic P (Zou; Binkley; Caldwell, 1995). P-solubilizing edaphic microorganisms are a functional group that mainly include bacterial genera (free-living or in symbiosis with plants) compared to actinomycete and fungi genera, which have the capacity to solubilize mineral phosphates that have been fixed in soils and cannot be used by plants in their nutrition; therefore, its ecological role is essential (López, 2022). The main mechanism of action of the P solubilizing functional group is the decrease in the pH of the extracellular medium through the release of low molecular weight organic acids (Mantilla; Esquivel-Ávila; Negrete-Peña, 2011).

Presumably, the release of low molecular weight organic acids is more intense and active in AAG and CAD soils and consequently there is greater solubilization of P, fixed by edaphic minerals, so that this nutrient is more available to plants in the soil solution, which can reduce phosphorus fertilizer applications, production costs and promote environmentally friendly management of this nutrient, mainly in CAD. López (2022) highlights that this functional group with the ability to solubilize P is multifunctional due to its contribution mainly to the support and regulation ecosystem services that arise in agroecosystems and ecosystems, which promote the growth and development of productive plant and auxiliary biodiversity.

Functional groups of edaphic microbes that participate in the biogeochemical carbon cycle

The first stage of the carbon cycle consists of the reduction or fixation of CO2 from the atmosphere through photosynthetic autotrophic organisms (plants, algae and cyanobacteria) and chemosynthetic autotrophic bacteria. In the second stage of this cycle, in agroecosystems and ecosystems, fresh organic matter from plant remains (straw, leaves, peels, fruits and roots etc.) is mineralized; whose main biopolymer (Linear Polysaccharides D-glucose) is cellulose (15 to 60 g per 100 g of dry matter). A complex of cellulolytic enzymes (C1: exo-β-1,4-glucanase, Cx: endo-β-1,4-glucanase, and Cb: β-D-glucoside glucohydrolase E.C.3.2.1.21) present in a variety of bacteria, actinomycetes and fungi hydrolyzes this linear polysaccharide of D-glucose, which transforms it from cellobiose and cellotriose into the monosaccharide glucose, which is the main source of energy (C) for the growth of the edaphic microbiota (Frioni, 2006; Ovando-Chacón and Waliszewski, 2005). It is very likely that in the conventional agroecosystem (CAD) with greater metabolic activity of fungi capable of producing the enzyme complex to convert cellulose into glucose are attributed, according to Frioni (2006), to the application of synthetic nitrogen fertilizers, because the cellulolytic capacity of this functional group is stimulated and increases their populations. This same author points out that a pH close to neutrality favors the enzymatic activity of this functional group. López (2022) found that fungi that degrade organic matter are multifunctional because they can contribute to the solubilization of P, K and S, the production of hormones for plant growth, the natural biocontrol of pests and pathogens and the natural bioremediation of soils.

Fungi-bacteria ratio as an indicator of soil quality or health

From an ecological perspective, “soil quality” is its capacity to accept, store and recycle water, minerals and energy for the production of productive plant biodiversity, and the preservation of a healthy environment (Arshad and Coen, 1992). This concept is functional (Estrada-Herrera et al., 2017) and includes indicators that serve for the evaluation of the physical, chemical and biological characteristics of soils because they are related to each other, and actively participate in the production and stability of agroecosystems and are the foundation for their sustainability (Garcia; Ramirez; Sánchez, 2012). The fungi-bacteria ratio is a good indicator for the evaluation of soil quality or health due to its sensitivity to the reaction to agronomic management and edaphoclimatic conditions (Bobadilla, 2022; Fernández et al., 2018).

Bobadilla (2022), in a preliminary study of microbiota, in 11 agroecosystems with different management and edaphoclimatic conditions in Zamorano, Honduras, determined a range of the fungi-bacterial ratio from 0.004, in an intensive agroecosystem (0.4%), to 1.714, in an organic agroecosystem (171.4%). In agroecosystems, fungi are less abundant compared to bacteria (López, 2022; Salazar-Centeno et al., 2021), but they are larger in size and biomass (Mora-Delgado; Silva-Parra; Escobar-Escobar, 2019), whose participation in the decomposition of organic matter is appreciable because the majority of these communities live in dead organic matter (INIAP, 2002) and are capable of biodegrading cellulose (15 to 60%), hemicellulose (10 to 30%) and lignin (5 to 30%), which are the most abundant polymers in plants (Frioni, 2006). Both groups participate in the processes of mineralization of organic matter and solubilization, which release: N, P, potassium (K), calcium (Ca) and sulfur (S) (Perez-Perez et al., 2021; Ramos-Salazar et al., 2022).

The results of the fungi-bacteria ratio confirm that the reproductive capacity of both groups is very sensitive to agronomic management by the producing families and to the edaphoclimatic conditions. The lower fungi-bacterial ratio in the TAM is attributed to the fact that the soil of this agroecosystem remains without plant cover (Table 1), at its moderate salinity (2.67 dS m-1), to a higher percentage of total nitrogen (tN%=0.45) in the soil, to a higher availability of P (217 ppm in 100 g of soil) and to a lower C/N ratio (5.2) of the OM (Tables 2 and 5), which restrict the reproductive capacity of edaphic fungi. Opposite to this situation, the TAG soil covered with a mulch of organic matter (Table 1), a moderately acidic pH (5.96), with medium salinity (2.62 dS m-1), with a percentage of total nitrogen of 0.25 and with a P availability of 206 ppm in 100 g of soil promote greater production of CFU g-1 of soil of fungi (Tables 2 and 5).

In the literature it is reported that these functional groups, in addition to contributing to natural biofertilization through their ability to fix N2 from the atmosphere, oxidize the NH4+ and NO₂-, to solubilize tricalcium phosphates (Clavijo et al., 2012) and to produce cellulolytic enzymes, they can synthesize metabolites or growth-regulating substances (auxins, gibberellins, cytokinins, ethylene and abscisic acid), which promote natural biostimulation (Hernández-Rodríguez et al., 2014; Pedraza et al., 2010); as well as the natural biocontrol of pests and edaphic pathogens (Clavijo et al., 2012) through different mechanisms of action (Competence for nutrients and space, induction of systemic plant resistance, production of antibiotics, siderophores, enzymes lithics and volatile and diffusible compounds).

CONCLUSIONS

The reproduction of diazotrophic bacteria, NH4+ and NO₂- oxidizing bacteria, and phosphorus-solubilizing microorganisms is more sensitive to the effects of edaphoclimatic conditions and the management practices carried out by peasant families in each agroecosystem. Therefore, these conditions can favor or disfavor the reproduction of fungi or bacteria, influencing the fungus-bacteria ratio. In contrast, populations of NO2- oxidizing bacteria are more stable, followed by populations of cellulolytic fungi.

CFU g-1 of soil were quantified for diazotrophic microorganisms, NH4+ and NO2- oxidizers, P solubilizers, cellulolytic fungi, and total fungi, whose populations contribute to natural biofertilization, biostimulation, biological control and bioremediation of soil. These functions facilities the development of soils that are suppressive, balanced, and capable of regulating edaphic pests and pathogens. This condition is more easily achieved in AAG and CAD due to the more balanced fungi-bacteria ratio.

In the four agroecosystems, it is essential to implement technologies, practices, and management systems that support productive and auxiliary biodiversity. These measures should promote the positive functionalities of associated biodiversity. To achieve this, the reference values, criteria, and judgments from this baseline must be considered for monitoring soil quality or health.

ACKNOWLEDGMENTS

We thank to the peasant families of Miguel and Paulo Gauliski, Lola Céspedes and Taita Bubrosky, Delia Caballero and Enrique Kemper, Sixto Acuña (RIP) and Rosa Bustos, for providing their knowledge and paving the way for the construction of agroecological territories. We would also like to thank Agr. Eng. María Sol Gilardino for her collaboration in the preparation of the maps.

Copyright (©) 2024 Stella Maris Mangione, Dennis José Salazar Centeno, Nora Trejo, Liliana Rosa Galián.

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Revista Brasileira de Agroecologia
ISSN 1980-9735

Publicação da Associação Brasileira de Agroecologia - ABA-Agroecologia em cooperação com o Programa de Pós-Graduação em Meio Ambiente e Desenvolvimento Rural - PPG-Mader, da Universidade de Brasília – UnB

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