Elke Jurandy Bran Nogueira Cardoso

Soil health: looking for suitable indicators. What should be considered to assess the effects of use and management on soil health?

Soil Health refers to the ecological equilibrium and the functionality of a soil and its capacity to maintain a well balanced ecosystem with high biodiversity above and below surface, and productivity. To understand and use soil health as a tool for sustainability, physical, chemical, and biological properties must be employed to verify which respond to the soil use and management within a desired timescale. Attributes with a rapid response to natural or anthropogenic actions are considered good indicators of soil health. Among the physical indicators, soil texture, aggregation, moisture, porosity, and bulk density have been used, while among chemical indicators total C and N, mineral nutrients, organic matter, cation exchange capacity, among others are well established. However, most of them generally have a slow response, when compared to the biological ones, such as microbial biomass C and N, biodiversity, soil enzymes, soil respiration, etc., in addition to macro and mesofauna. Thus, a systemic approach based on different kinds of indicators (physical, chemical and biological) in assessing soil health would be safer than using only one kind of attribute. Many human activities have caused desertification, loss of biodiversity, disruption of aggregates, loss of organic matter and nutrients, among others. Today, it is imperious to maintain soil health and productivity with increasing emphasis on reforestation and recuperation of degraded areas through the use of organic amendments, reintroduction of plants, soil fauna and microorganisms. This review focused on an integrative view on indicators of soil health to be used as tools for prediction of sustainability in production systems.

Isolation, selection and characterization of root-associated growth promoting bacteria in Brazil Pine (Araucaria angustifolia).

Araucaria angustifolia, a unique species of this genus that occurs naturally in Brazil, has a high socio-economic and environmental value and is critically endangered of extinction, since it has been submitted to intense predatory exploitation during the last century. Root-associated bacteria from A. angustifolia were isolated, selected and characterized for their biotechnological potential of growth promotion and biocontrol of plant pathogenic fungi. Ninety-seven strains were isolated and subjected to chemical tests. All isolates presented at least one positive feature, characterizing them as potential PGPR. Eighteen isolates produced indole-3-acetic acid (IAA), 27 were able to solubilize inorganic phosphate, 21 isolates were presumable diazotrophs, with pellicle formation in nitrogen-free culture medium, 83 were phosphatases producers, 37 were positive for siderophores and 45 endospore-forming isolates were antagonistic to Fusarium oxysporum, a pathogen of conifers. We also observed the presence of bacterial strains with multiple beneficial mechanisms of action. Analyzing the fatty acid methyl ester (FAME) and partial sequencing of the 16S rRNA gene of these isolates, it was possible to characterize the most effective isolates as belonging to Bacillaceae (9 isolates), Enterobacteriaceae (11) and Pseudomonadaceae (1). As far as we know, this is the first study to include the species Ewingella americana as a PGPR.

Arbuscular mycorrhizal fungi associated with Araucaria angustifolia (Bert.) O. Ktze

Specimens of Araucaria angustifolia from a native forest reserve and a reforested area in the State Park of Campos do Jordão were studied to determine the number and diversity of spore populations of arbuscular mycorrhizal fungi (AMF) and root colonization. Six randomly chosen plots (planted with 8- to 12-year-old plants) were delimited, four in the native forest and two in the reforested area. Rhizosphere and root samples were collected during two periods of the year corresponding to the rainy and dry seasons. A greenhouse experiment was set up for multiplication of field propagules (from the native forest and reforested area) for two consecutive generations. Araucaria leaves from the experimental plots were collected during the first sampling for nutrient analysis. Twenty-four AMF taxa were found and percent AM colonization was determined in all plots. Not all AMF species observed in the field were re-isolated through the recovery pot cultures, even after a second cultivation cycle. The foliar nutrient analysis showed higher nutrient levels in plants from the native forest than the reforested area. Generally, spore richness and diversity were highest during the warmer and more humid period and in the native forest plants.

Earthworm ecotoxicological assessments of pesticides used to treat seeds under tropical conditions

Ecotoxicological laboratory tests (lower-tier tests) are fundamental tools for assessing the toxicity of pesticides to soil organisms. In this study, using these tests under tropical conditions, we quantified the impact of the insecticides imidacloprid, fipronil, and thiametoxam, and the fungicides captan and carboxin+thiram, all of which are used in the chemical treatment of crop seeds, on the survival, reproduction, and behavior of Eisenia andrei (Oligochaeta). With the exception of imidacloprid, none of the pesticides tested caused mortality in E. andrei in artificial soils. The LC(50) of imidacloprid was estimated as 25.53 mg active ingredient kg(-1) of dry soil. Earthworm reproduction rates were reduced by imidacloprid (EC(50)=4.07 mgkg(-1)), fipronil (EC(20)=23.16 mgkg(-1)), carboxin+thiram (EC(50)=56.38 mgkg(-1)), captan (EC(50)=334.84 mgkg(-1)), and thiametoxam (EC(50)=791.99 mgkg(-1)). Avoidance behavior was observed in the presence of imidacloprid (AC(50)=0.11 mgkg(-1)), captan (AC(50)=33.54 mgkg(-1)), carboxin+thiram (AC(50)=60.32 mgkg(-1)), and thiametoxam (AC(50)=>20 mgkg(-1)). Earthworms showed a preference for soils with the insecticide fipronil. Imidacloprid was the most toxic of the substances tested for E. andrei. The avoidance test was the most sensitive test for most pesticides studied, but results varied between pesticides. These results offer new insights on the toxicity of pesticides used to treat seeds in tropical regions. However, they should be complemented with higher-tier tests in order to reduce the uncertainties in risk assessment.

Earthworm populations sampled using collection methods in atlantic forests with Araucaria angustifolia

Araucaria angustifolia, also known as the Parana Pine is an endangered tree species in Brazil and little is known of the diversity of soil invertebrates inhabiting these forests. Therefore, the present study was set up to evaluate the biomass and diversity of earthworms in natural and reforested Araucaria plots, impacted or not by fire, and to identify the most efficient earthworm collection method. Four study areas included: native forest with Araucaria (NF); Araucaria reforestation (R); Araucaria reforestation submitted to an accidental fire (RF); and native grass pasture with native Araucaria and submitted to an intense accidental fire (NPF). Five soil samples containing the earthworm community were taken in a 0.3 ha area in each of the forest sites, close to five Araucaria trees selected at random. Three collection methods were tested: application of dilute Formol (0.5%) to the soil surface, handsorting of small (25 ´ 25 cm) or large (40´ 40 cm) monoliths. Five earthworm species were found: the native Glossoscolex sp.1, Glossoscolex sp.2, Glossoscolex bondari and Urobenus brasiliensis (Glossoscolecidae), and the exotic Amynthas corticis (Megascolecidae). Formol was more efficient for collecting A. corticis, found in much higher abundance and biomass in NF than in the other areas. Larger handsorted samples were more efficient for capturing Glossoscolex species, mainly present in RF and NPF. For adequate characterization of earthworm abundance and biomass in these Araucaria forests, both the Formol and the larger monolith methods are recommended.

Phosphorus availability changes the internal and external endomycorrhizal colonization and affects symbiotic effectivenes

Despite the awareness that high phosphorus (P) availability decreases the mycorrhizal root colonization in higher plants, the effects on the external mycelium are contradicting. The aim of this work was to assess the external mycelium of the arbuscular mycorrhizal fungi (AMF) Glomus intraradices and Gigaspora rosea, associated to soybean under increasing P levels (0, 25, 50, 100 and 200 mg kg-1). The tested hypotheses were: a) the amount of external mycelium depends on the fungal species; b) the P levels affect diferentially each mycorrhizal species; c) the mycorrhizal effectiveness depends on the amount of external mycelium. Mycorrhizal stimulus on plant biomass occurred at P levels of 0, 25 and 200 mg kg-1. Mycorrhizal root colonization and total external mycelium (TEM) decreased with increasing P levels. At zero P level, G. rosea produced less TEM than G. intraradices, which may be related to the lower mycorrhizal effectiveness for G. rosea. Both AMF increased the active external mycelium along P levels, but this increase was not related with symbiotic effectiveness. TEM was found to be closely related to root colonization and mycorrhizal effectiveness. The root colonization and TEM are mutually afected by P availability. Althoug G. intraradices produced more TEM than G. rosea along the P levels, they seemed to affect similarly the TEM for both AMF. More AMF species should be assessed in order to attest whether P levels affect the external mycelium differentially among them.

Fósforo adicionado e fungos micorrízicos arbusculares no crescimento e nutrição mineral de limoeiro-cravo [Citrus limonia (L.) OSBECK]

The aim of this work was to evaluate the influence of P levels and arbuscular mycorrhizal fungi (AMF) on growth and mineral nutrition of Citrus limonia. The experiment was conducted under greenhouse conditions, with a completely randomized 6 x 3 factorial design, with six P levels (0, 50, 100, 150, 200 and 250 mg kg-1 of substrate), two species of AMF (G. etunicatum and G. intraradices) and a control without AMF, with three replicates per treatment, using 1.7 dm-3 pots. Five months after transplanting, plants were assessed for height, stem diameter, shoot dry matter, shoot nutrient content, root colonization and substrate analysis for active (AEM) and total (TEM) extraradical AMF mycelium length. Citrus limonia presented high mycorrhizal dependence on nutrient absorption, mainly when inoculated with Glomus intraradices, which promoted greater plant height, larger stem diameter and greater shoot dry matter production. Only G. intraradices promoted detectable root colonization, with percent root colonization being inversely proportional to the applied P level. AEM and TEM increased in accordance with P levels, and high correlations were found between the former and nutrient absorption. Although no root colonization could be observed, G. etunicatum produced AEM and TEM, which may show a saprophytic capacity for survival in soil.

Seed dressing pesticides on springtails in two ecotoxicological laboratory tests

Terrestrial ecotoxicological tests are powerful tools for assessing the ecological risks that pesticides pose to soil invertebrates, but they are rarely used to evaluate seed dressing pesticides. This study investigated the effects of seed dressing pesticides on survival and reproduction of Folsomia candida (Collembola), using standardized ecotoxicological tests (after ISO guidelines with few adaptations for tropical conditions). Commercial formulations of five seed dressing pesticides were tested individually in Tropical Artificial Soil (TAS): the insecticides imidacloprid, fipronil, thiametoxam, and the fungicides captan and carboxin+thiram. Thiametoxam, captan, and carboxin+thiram were only lethal to F. candida at the highest concentration tested (1000mg of active ingredient kg(-1) of dry soil). Imidacloprid and fipronil were lethal at lower concentrations (100 and 10mg a.i. kg(-1) soil d.w, respectively), however, these concentrations were much higher than those predicted (PEC) for soil. Imidacloprid and fipronil were the most toxic pesticides in both tests, reducing significantly collembolan reproduction (EC20=0.02 and 0.12mga.i.kg(-1) soil d.w, respectively). Further studies under more realistic conditions are needed, since imidacloprid and fipronil reduced collembolan reproduction at concentrations below or close to their respective PECs.

Biodiversity and distribution of arbuscular mycorrhizal fungi in Araucaria angustifolia forest

Araucaria angustifolia (Bert.) O. Ktze. is an endangered Brazilian coniferous tree that has been almost exterminated in the native areas because of uncontrolled wood exploitation. This tree has been shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) and, therefore, AMF may be essential for forest sustainability and biological diversity. Root colonization, density and diversity of AMF spores were assessed in two Araucaria forest stands at the State Park of Alto Ribeira (PETAR), at two sampling dates: May and October. A comparison was made between a mature native stand composed of Araucaria trees mixed into a variety of tropical trees and shrubs, without any sign of anthropogenic interference (FN) and an Araucaria stand planted in 1987 (R), which has been used as a pasture. Assessments included percent root colonization, AMF spore numbers and species richness, Simpsons dominance index (Is), and Shannons diversity index (H). Mycorrhizal root colonization did not differ between ecosystems in May. In October, however, the native stand (FN) presented a higher colonization than the planted forest (R), and the root colonization was more intense than in May. When considering both sampling periods and forests, 27 species of AM fungi, with higher numbers of spores in FN than in R were found. Canonical discriminant analysis (CDA) indicated Shannons diversity index as the ecological attribute that contributed the most to distinguish between forest ecosystems, with higher value of H in FN in relation to R. CDA showed to be a useful tool for the study of ecological attributes.

URBAN SOLID WASTE MATURITY

O processo de compostagem de lixo pre-digerido, produzido na Usina de Compostagem de Vila Leopoldina do municipio de Sao Paulo acondicionado em cestos telados, foi avaliado atraves das variaveis: pH, P total, temperatura, producao de CO2, materia orgânica e N total durante um periodo de 52 dias. O lixo foi de 1 m de diâmetro por 1,5 m de altura, revolvido e umedecido semanalmente. Ao final do periodo estudado, as variaveis producao de CO2, temperatura, materia orgânica total e relacao C/N apresentaram seus valores reduzidos, enquanto o pH e os teores de N e de P total atingiram seus valores maximos. Os dados permitiram concluir que o periodo avaliado foi suficiente para a maturacao do composto de lixo.