Elena Blume

Surface and subsurface microbial biomass, community structure and metabolic activity as a function of soil depth and season

Microbial biomass, size and community structure along with an estimate of microbial activity and soil chemical parameters were determined at three depths in two soils (e.g. sandy loam Ultic Hapludalf and silt loam Mollic Hapludalf ) replicated three times under one winter and summer season. Microbial biomass and community structure were estimated from phospholipid-PO4 content and fatty acid methyl ester (FAME) measurements. Microbial activity and assimilative capacity were estimated using a 3 H-acetate incorporation into phospholipids and by incubating the soil samples at the average winter and summer temperatures, 3 and 20 ◦ C, respectively. We found that the size of the microbial biomass in both the surface and the subsurface soils was not significantly affected by the seasonal variation but activity increased by as much as 83% at the summer temperatures in the surface soil. We demonstrated using FAME analysis that for both soils seasonal changes in the subsurface microbial community occurred. These findings suggest that winter conditions will shift the population activity level in both the surface and subsurface systems and the biochemical structure of the community in the subsurface. In all cases, the inorganic chemical properties of the soil, as a function of season, remained constant. The greatly increased activity of microbial population at the higher temperature will favor the capacity of the system to utilize nutrients or organic materials that may enter soil. During low temperature seasons the capacity of either surface or subsurface soils to assimilate materials is generally diminished but the reduction reflects changes in metabolism and not a reduced biomass size.

Dinâmica da agregação de um solo franco-arenoso em cinco sistemas de culturas em rotação e em sucessão

SUMMARY : AGGREGATION DYNAMICS OF A SANDY SOIL UNDER FIVECROPPING SYSTEMS IN ROTATION AND IN SUCCESSION Cover crops along with proper soil management recover or maintain soil physicalproperties such as aggregation. The objective of this study was to determine the effect ofcropping systems, cover crops, and soil organic matter (SOM) content on the temporalvariation of soil aggregation in an Hapludalf in its natural state and under different croppingsystems. The experiment was conducted at the experimental station of the Soil Departmentof the UFSM, Brazil. Undisturbed soil samples were collected in 60 day-intervals throughoutan year (Ocotober/1997 to October/1998) from a depth of 0–0.05 m and analyzed foraggregate stability, SOM content, and selected physical and chemical properties. The greateststructural stability was observed under grassland and the smallest stability for bare soildue to the intense soil tillage and reduction in SOM, increasing the proportion of smallaggregates. Cover crops formed and stabilized soil aggregates directly, and the stabilityand proportion of aggregates were greater under cultivation systems that increase SOMand cover the soil during the whole year. Different cropping sequences affect soil aggregationdistinctly, depending on the time of the year and time of establishment of the crops.Index terms: soil structure, aggregate stability, cover crops, soil management.

Variabilidade espacial de propriedades físico-hídricas do solo, da produtividade e da qualidade de grãos de trigo em Argissolo Franco Arenoso sob plantio direto 1

Spatial varibility of soil physico-hydrical properties is related to soil genesis and management, and affect crop production. The objectives of this study were to identify and to relate spatial variability of saturated hydraulic condutivity (K(qs)), soil mechanical resistance (R), soil texture, and A horizont depth, of a Typic Hapludalf under no-till, with wheat yield and hectoliter weight. This experiment was conducted in the winter of 1999, on a 1.51 ha no-till wheat field. Soil and plant characterization was done on five transects with 100m in the East-West direction, with sampling points 10m apart. Values of R for the depths of 5cm, 7.5cm, 10cm and 15cm and A horizont depth showed normal distribution. Spherical model semivariograms were adjusted for K(qs), R in the 30cm depth, clay content, and A horizont depth. Exponential model for R in the 2.5cm and 5cm depths, clay and silt content, and wheat yield and hectoliter weight. For the 7.5cm, 10cm, 12.5cm, 15cm and 17.5cm depths, R semivariograms showed pure nugget effect; in these depths the machinery traffic and previous soil management effects are prominent. Wheat yield and hectoliter weight did not correlate with K(qs) and R. When evaluating the spatial variability in R for soil layers deeper than 5cm, the distance between samples points should be smaller than 10m.

Fungos antagonistas a Sclerotinia sclerotiorum em pepineiro cultivado em estufa

White mold caused by Sclerotinia sclerotiorum may severely damage vegetables grown in greenhouses. To develop a biological control program for this pathogen proper antagonists are needed. This work aimed to select efficient fungi antagonists for controlling S. sclerotiorum on cucumber (Cucumis sativus) grown in greenhouses, and to evaluate the effect of the antagonist on the growth of the vegetable. An isolate of S. sclerotiorum obtained from cucumber and 112 fungi isolates belonging to four genera were used: Trichoderma, Fusarium, Penicillium, and Aspergillus. For the in vitro experiment, the cellophane method was used and eight Trichoderma virens isolates were selected that had inhibited the pathogen growth by 94 to 100%. Greenhouse experiments used sterilized and non-sterilized substrate in plastic cups and non-sterilized substrate in plastic bags. The substrate was inoculated with S. sclerotiorum and the eight isolates of T. virens were used as antagonists. All eight isolates controlled damping-off of plants caused by S. sclerotiorum, but the effect on cucumber growth varied according to the isolate and the substrate treatment.

Avaliação da qualidade de sementes e mudas de cedro.

Belonging to the Meliaceae family, cedro ( Cedrela fissilis Vell.) presents a great economical and ecological importance. The wood is light and easy to work, being suggested to the manufacturing of furniture in general, also it is used to reset degraded areas. The objective of this work was to evaluate the quality of Cedrela fissilis seedlings and seeds from Rio Grande do Sul, Santa Catarina and Parana, through the accomplishment of varied tests of vigor, test of health and evaluation of the quality of seedlings produced from these seeds. The present study showed that the presence of fungi pathological potential – Aspergillus spp. and Penicillium spp. – can cause losses in the germination. Considering tests with seeds collected in the different states of the South Region, it was possible to verify that differences of the vigor levels exist. The fungi found in the seeds can cause damages in the production.

Superação de dormência na qualidade de sementes e mudas: influência na produção de Senna multijuga (L. C. Rich.) Irwin & Barneby

The objective of this work was to determine the physiological and sanitary quality of Senna multijuga seeds related to the methods of dormancy overcoming and the influence on the seedlings quality. The seeds had been submitted to the following methods :immersion in water fervent, the seeds had been immersed in water, at 100°C, until cooling for 24 hours; acid escarification, where the seeds had been immersed in sulfuric acid (H 2 SO 4 ) 90%, for 10 and 20 minutes, and control (without treatment). The tests of sanity, germination and tetrazolium had been carried through, and were evaluated the quality of the seedlings. For the germination of the evaluation an factorial project was used (4 X 2), with four methods of dormancy X two light periods, for substrate paper and vermiculite. The acid scarification consisted in the method most efficient for the dormancy of Senna multijuga seeds. Penicillium sp. and Aspergillus sp. they had for its increased incidence when the seed coast was damaged by the acid scarification for 20 minutes. The control of Fusarium spp. increases gradual with the increase of the time of sulfuric acid exposition.

Maturação fisiológica e coleta de sementes de Eugenia uniflora L. (Pitanga), Santa Maria, RS.

This study aimed to accompany the physiologic maturation, their indicative parameters and to identify the moment adapted for the seed harvest of Eugenia uniflora , evaluating also the incidence of fungus in fruits and seeds. The research was carried out from August to October of 2004 in Santa Maria, RS. Samples of fruits and seeds were collected weekly, from three main trees, with beginning to the seven days after the anthesis (DAA) and end to the 77 DAA. The observed variables were: length, diameter, weight and sanity of fruits and seeds and moisture content, dry mass and germination of the seeds. The appropriate time for the seed harvest, in the period and place being studied, occurred between 56 and 63 DAA, when the fruits presented red coloration and the seeds high germination. In that period, the size and the weight of fruits and seeds reached their maximum values and the moisture content and dry mass of the seeds showed tendency to the stabilization. The fungi Cladosporium sp. and Alternaria sp. presented the largest incidence taxes in the fruits and in the seeds and they can influence the storage and the germination Eugenia uniflora seeds.

Variabilidade genética na região its do rDNA de isolados de trichoderma spp. (Biocontrolador) e Fusarium oxysporum f. sp. Chrysanthemi

A analise de caracteristicas morfologicas e culturais podem nao ser suficientes para uma caracterizacao precisa das especies de Trichoderma e Fusarium. Objetivou-se, neste trabalho, caracterizar a regiao do Espaco Interno Transcrito (ITS) do rDNA dos isolados UFSMT15.1, UFSMT16 e UFSMT17 de Trichoderma spp. utilizados no biocontrole de Fusarium oxysporum f. sp. chrysanthemi (isolado) UFSMF6. A extracao de DNA de cada isolado foi realizada a partir de micelio produzido em meio liquido Batata-Dextrose. As amostras de DNA genomico foram submetidas a Reacao em Cadeia da Polimerase (PCR) com os oligonucleotideos iniciadores universais ITS1 e ITS4 e o produto gerado foi sequenciado. Os fragmentos gerados pela amplificacao da PCR foram tratados com as enzimas de restricao HaeIII, HinfI e MboI. As regioes ITS1, ITS2 e 5.8S do rDNA desses isolados fungicos foram amplificadas com sucesso. A regiao ITS dos isolados UFSMT15.1, UFSMT16 e UFSMT17 de Trichoderma e o isolado UFSMF6 de Fusarium apresentaram uma banda simples com um fragmento de aproximadamente 600 pares de base (pb). As enzimas de restricao HaeIII, HinfI e MboI geraram polimorfismo de bandas entre os isolados. Com base nas analises da sequencia de DNA, os isolados UFSMT15.1, UFSMT16, UFSMT17 e UFSMF6 apresentaram maior similaridade com as especies Trichoderma koningiopsis, Hypocrea virens, Hypocrea lixii e Fusarium oxysporum, respectivamente.

MATURAÇÃO FISIOLÓGICA DE SEMENTES DE Erythrina crista-galli L.

The objective of this research was to study the maturation process of Erythrina crista-galli L. seeds to determinate the ideal collect period. In this regard, six trees located in Santa Maria - RS were used from which were collected weekly, starting with fruits until seeds maturation. The parameters observed to indicate seed maturation were: fruit and seed dimensions; seed fresh and dry matter; moisture content, germination test (expressed by normal seedlings) and vigor (first count of germination). The seeds dimensions were highest in the same period of maximum germination, with values 167.0, 8.72 and 8.60 mm of length, thickness and width, respectively. The seeds moisture content could be used to indicate the seeds maturation, and also seeds fresh and dry matter with maximum values on the eighth week, 31.6 %, 0.693 and 0.474 g/seed, respectively. The Erythrina crista-galli has dormant seeds after physiological maturation, with low percentage of germination on the tenth week after anthesis. The point of physiological maturation in Santa Maria - RS conditions happens on the eighth week after anthesis, with germination percentage of 50%, which were indicate by all parameters observed.

Sanitary and physiological quality of soybean seeds treated with bioprotector and fungicide

The objective of this study was to evaluate the effect of the bioprotector Agrotrich® and the fungicide Vitavax-Thiram®, alone or combined, on the sanitary and physiological quality of soybean seeds, through assessments of health, germination, seedling evaluation , emergence in a greenhouse and in the field. The experiment was conducted at the Plant Pathology Laboratory and in the experimental area of the Department of Plant Health Defense at the Federal University of Santa Maria, from June to November 2007. In the seed health assessment, the treatments with chemical fungicide, alone or in combination, showed the lowest values of fungus incidence. For germination and first count, the treatment using half the dosage of the products obtained the best result. In the assessment of seedlings in a greenhouse, the treatments did not differ among themselves, for any of the variables, and nor for emergence, emergence speed index, first, second and third leaflet, in the field. In the analysis of correlation between the fungi and the physiological quality variables, a negative effect predominated. The combination of products at half the doses showed better effect on seed quality assessments.