Pedro José Valarini

Discrimination of management effects on soil parameters by using principal component analysis: a multivariate analysis case study

One of the major interests in soil analysis is the integrated evaluation of soil properties, which might be indicators of soil quality. Unsupervised methods of multivariate statistics are powerful tools for this integrated assessment and can help soil researchers to extract much more information from their data. A multivariate study was carried out in three farms from Guaira, State of Sao Paulo, Brazil. Conventionally managed plots that intensively utilized pesticides and chemical fertilizers were compared with both non-disturbed forest areas and alternatively managed plots. The latter were under ecological farming employing effective microorganisms (EM) integrated with crop residues. Eight soil parameters were determined for each plot. Hierarchical cluster analysis (HCA) was used to verify the similarity among the plots. The multivariate approach of principal component analysis (PCA) allowed us to distinguish the areas as a function of the soil management and determine which are the most important parameters to characterize them. The forest areas presented higher microbial biomass with lower cellulolytics population than at cultivated sites. The alternative plots were characterized by higher microbial biomass and polysaccharide content with lower phosphate solubilizers and cellulolytics microorganisms colony counts than at the conventional areas. The higher observed levels of microbial biomass and polysaccharide content in the alternative areas can be attributed to the effects of the alternative soil amendment. All these effects can be clearer globally visualized with the aid of PCA, through the biplots.

Avaliação do Uso de Métodos Quimiométricos em Análise de Solos

One of the major interests in soil analysis is the evaluation of its chemical, physical and biological parameters, which are indicators of soil quality (the most important is the organic matter). Besides there is a great interest in the study of humic substances and on the assessment of pollutants, such as pesticides and heavy metals, in soils. Chemometrics is a powerful tool to deal with these problems and can help soil researchers to extract much more information from their data. In spite of this, the presence of these kinds of strategies in the literature has obtained projection only recently. The utilization of chemometric methods in soil analysis is evaluated in this article. The applications will be divided in four parts (with emphasis in the first two): (i) descriptive and exploratory methods based on Principal Component Analysis (PCA); (ii) multivariate calibration methods (MLR, PCR and PLS); (iii) methods such as Evolving Factor Analysis and SIMPLISMA; and (iv) artificial intelligence methods, such as Artificial Neural Networks.

Effect of Compost Application on Some Properties of a Volcanic Soil from Central South Chile

Soil compost application is a common soil management practice used by small farmers of Central-South Chile that produces positive effects on soil properties and also promotes presence and activity of arbuscular mycorrhizal fungi (AMF). This fungi form symbiosis with plant roots improving plant nutrition, as well as producing glomalin, a glycoprotein that has been associated with soil aggregation stability. Therefore, the aim of this study was to evaluate, in an Ultisol from Central-South Chile, the effect of different doses of compost on some soil characteristics at the end of the third year of a crop sequence including wheat (Triticum aestivum L.), bean (Phaseolus vulgaris L.), and grassland (Lolium multiflorum Lam. associated with Trifolium repens L.). Studied soil characteristics included chemical (pH, available-P, organic C), biological (C and N biomass, AMF spore number, root colonization percentage, mycelium length, and glomalin content), as well as physical parameters (water holding capacity [WHC], and water stable aggregates [WSA]). Results showed that, in general, compost application increased soil

Integrated evaluation of soil quality after the incorporation of organic matter and microorganisms

The soil quality was evaluated following the addition of organic matter and microorganisms to a clay loam soil collected in Aranjuez (Madrid) under controlled conditions of temperature and moisture, and over a period of three months. The following treatments were carried out: soil (control); soil + 50 t/ha of animal manure (E50); soil + 50 t/ha of animal manure + 30l/ha of effective microorganisms (E50EM); soil + 30 t/ha of combination of various green crop residues and weeds (RC30) and soil + 30 t/ha of combination of various green crop residues and weeds + 30l/ha of effective microorganisms (RC30EM). The soil samples were taken before and after the incubation and analysed using physical, chemical and microbiological parameters. A significant increase in the production of polysaccharides and alkaline phosphatase and esterase enzymes in the treatments E50EM and RC30EM was observed, being in direct correlation with the humification of the organic matter, with the water retention at field capacity, and with the cationic exchange capacity (CEC). It can be concluded that the incorporation of microorganisms EM potentialized the soil biological activity and improved physico-chemical soil properties, contributing to a quick humification of fresh organic matter. Those findings were proved by microbiological activities of exopolysaccharides by alcaline phosphatase and esterase enzymes, which can be used as earlier and integral soil health indicators.

Análise integrada de sistemas de produção de tomateiro com base em indicadores edafobiológicos

A analise integrada de indicadores edafobiologicos ligados ao manejo do solo constitui uma ferramenta importante para estimar niveis de sustentabilidade do agroecossistema, detectando-se pontos criticos para a devida correcao de manejo. Essa ferramenta foi empregada na avaliacao de sistemas de producao orgânica e convencional de tomate, em cultivo protegido e a campo aberto, no estado de Sao Paulo. Tomaram-se como referencia solos de mata nativa e/ou pastagem natural, dependendo do local de estudo. Em Serra Negra, o solo sob sistema orgânico apresentou maior capacidade de campo e teor de argila dispersa mais baixo, indicativos da estabilidade dos agregados. No sistema convencional observou-se uma elevada condutividade eletrica, evidenciando a alta disponibilidade de sais soluveis. A analise de componentes principais (ACP) permitiu concluir que ha maior grau de similaridade entre o solo sob sistema orgânico e aqueles das bases referenciais, com respeito aos indicadores quimicos e biologicos. Constatou-se que C org, N total, polissacarideos, FDA (hidrolise de diacetato de fluoresceina) e atividade enzimatica de desidrogenase estao positivamente relacionados com o sistema orgânico, a mata nativa e a pastagem. Em contrapartida, a saturacao por bases (V%), pH, teores de Mn, Mg e Ca, bem como a razao de dispersao estao inversamente relacionadas ao manejo orgânico. Ja em Araraquara, os resultados da ACP distinguiram as areas organicamente cultivadas das matas nativas, principalmente, com base nos indicadores biologicos.

Qualidade do solo em sistemas de produção de hortaliças orgânico e convencional

The soil is one of the most important sustainability columns of the production system. The integrated analysis of the edaphobiological attributes can be an important tool for soil quality evaluation. We evaluated the soil quality regarding the adopted agriculture practices, using the integrated analysis of physical, chemical and biological attributes. The research was carried out in Ibiuna and Socorro, Sao Paulo state, Brazil, in organic and conventional production, on small and family farms. Physical, chemical and biochemical parameters were evaluated during 2006 and 2007 in soils under vegetable cultivation, native forest or fallow, taken as reference of natural soil. Agricultural practices data were collected in each production system. The obtained data were submitted to principal component analysis (PCA). There was no pronounced grouping trend according to the production system, organic or conventional, but there was a grouping according to the soil use (forest/fallow land or cultivation). The PCA identified greater degree of similarity between Socorros cultivation soil and its respective controls compared to Ibiunas soil, clearly separated according to its use (forest or cropping), indicating better soil management in Socorro. In general, the results allow to conclude that agricultural practices in most of both organic and conventional production systems, caused soil degradation, due to, mainly, intensive soil tillage and no soil mulching, as indicated by the reduction of soil organic matter, microbial biomass, plant emergence and aggregate stability in cultivated areas relative to control ones.