Walmes Marques Zeviani

Modelagem da curva de retenção de água de Latossolos utilizando a Equação Duplo Van Genuchten

SUMMARY : MODELING THE WATER RETENTION CURVE IN OXISOLSUSING THE DOUBLE VAN GENUCHTEN EQUATION The clay fraction mineralogy and the granular structure of Oxisols in the Cerrado(Brazilian savanna) are the reason for the great volume of large pores as well as of extremelysmall pores, but no significant medium pore volume, resulting in low available water forplants. This study aimed to characterize and model the behavior of water retention in Oxisolswith different texture classes of the Cerrado region. Samples were collected from the Bwhorizon of 10 Oxisols under native vegetation. Water retention was measured at matric potentialsof 1, 2, 4, 6, 8, 10 kPa using a Richards plate, and the water retained in potentials of 1.500 and300.000 kPa determined by a thermocouple psychrometer model WP4-T Dewpoint PotentiaMeter. The double van Genuchten model was proposed to fit the experimental water retentiondata by non-linear fitting using software R 2.10.1. The relationship between the estimatedmodel parameters and the inflection point with soil texture properties was evaluated also bythe Pearson correlation test. Results indicated good fitting of the model and great predictionpower and correlation between the soil clay content and equation parameters (U

Disponibilidade hídrica e distinção de ambientes para cultivo de cafeeiros

This study was conducted in the districts of Sao Roque de Minas and Vargem Bonita, MG, with the aim to distinguish landscapes for coffee growing, with higher water available to the crop. Soil moisture was monitored in eight plots of coffee, and in five of them being also determined water availability for plants and soil bulk density. The plots are located in areas of Latosols and Cambisols. In one plot of each soil class, the distribution of the root system of coffee in the soil profile was studied. Soil moisture was monitored from April 2008 to February 2009, in the interval of 30 to 40 days. The soil depths of 0.2, 0.4, 0.8, 1.2 and 1.6 m were sampled, in line and between the lines of the coffee. The combination of the five plots, two sampling positions (line and between the lines) and five depths, formed the 50 Treatments used in the multivariate analysis. It was observed that soil moisture is lower in the line of coffee compared to between lines. The class of soil and plant age influence soil moisture and water availability to plants. The root system of coffee reached the depth of 1.5 to 1.7 m, in both studied soil classes. The 50 Treatments were grouped into 4, by means of the principal component analysis, according to the soil class and management.

Bimodal pore distribution on soils under conservation management system for coffee crop

This study aims at detailing bimodal pore distribution by means of water retention curve in an oxidic-gibbsitic Latosol and in a kaolinitic cambisol Latossol under conservation management system of coffee crop. Samples were collected at depths of 20; 40; 80; 120 and 160 cm on coffee trees rows and between rows under oxidic-gibbsitic Latosol (LVd) and kaolinitic cambisol Latossol (LVAd). Water retention curve was determined at matrix potentials (Ψm) -1; -2; -4; -6; -10 kPa obtained from the suction unit; the Ψm of -33; -100; -500; -1,500 kPa were obtained by the Richards extractor, and WP4-T psychrometer was used to determine Ψm -1,500 to -300,000 kPa. The water retention data were adjusted to the double van Genuchten model by nonlinear model procedures of the R 2.12.1 software. Was estimated the model parameter and inflection point slope. The system promoted changes in soil structure and water retention for the conditions evaluated, and both showed bimodal pores distribution, which were stronger in LVd. There was a strong influence of mineralogy gibbsitic in the water retention more negative than Ψm -1500 kPa, reflected in the values of the residual water content.

Antifungal activity and ultrastructural alterations in Pseudocercospora griseola treated with essential oils

Pseudocercospora griseola, the etiologic agent of angular leaf spot of common bean (Phaseolus vulgaris), is an important disease in all bean-producing regions worldwide and may cause extremely high yield losses. The control of this disease is made more difficult by the pathogens genetic variability and the inefficiency of fungicides. In this study, of 26 essential oils tested at different concentrations, 25 demonstrated efficiency in affecting the germination of strains 63-31 and 63-63 of the pathogen, reaching inhibition levels of between 80% and 100%. Cymbopogon citratus and Cymbopogon martinii inhibited conidia germination at all concentrations; Eugenia caryophyllata, Cinnamomum sp., Thymus vulgaris, Matricaria recutita, Cordia verbenacea, Origanum vulgare, Cymbopogon nardus, at 0.1 and 0.5%; and Zingiber officinale, Mentha arvensis, Chamaecyparis pisifera, Lavandula officinalis, Ocimum basilicum, Pimpinella anisum, Ocimum selloi, Baccharis dracunculifolia, Laurus nobilis, Citrus sinensis, Melaleuca alternifolia and Eucalyptus globulus, at 0.5%. The main constituents identified were cinnamaldehyde in Cinnamomum sp.; eugenol in E. caryophyllata; trans-β-farnesene in M. recutita; pulegone in C. verbenacea; thymol in T. vulgaris; geranial and neral in C. citratus, and geraniol in C. martini. Through transmission electron microscopy (TEM), it was verified that C. citratus, C. martini and E. caryophyllata presented direct fungitoxic action on P. griseola, causing severe damage to the cellular ultrastructure of the conidia, invalidating germination. These results indicated that essential oils are a promising alternative strategy for the control of angular leaf spot in bean, representing less risk to human health and the environment.

Alterações físico-químicas e movimentação de íons em Latossolo gibbsítico sob doses de gesso

The effect of gypsum on the point of zero charge-PZC, calcium, magnesium, potassium and sulfate dynamics, and water retention were evaluated in a very clayey dystrophic gibbsitic Red Latosol. Six doses of gypsum (corresponding to 0, 3, 6, 9, 12 and 15 Mg ha-1) and two water supply conditions (with and without water deficit) were imposed to soybean crop. Soil was sampled at the depths of 0-0.2 m and 0.7-0.9 m, representing the A and Bw horizons, respectively. Soil samples were placed in PVC tubes (0.2 m in length and 0.1 m of diameter), simulating two layers: the upper layer had A horizon soil, which was amended with dolomitic limestone; and the bottom layer had Bw horizon soil, under the natural pH. Both layers had soil density of 1 kg dm-3. The PZC was changed by gypsum; as gypsum dose increased, calcium concentration increased in both soil layers. There was no difference in S value in the upper layer due to gypsum; however it increased in the subsurface layer as gypsum was applied. Lower Mg concentration was found in the upper layer, whereas increases in Mg were noticed in the bottom layer as gypsum doses increased. No changes in water retention and K concentration were found in response to gypsum and water supply regimes.

Umidade do solo e doses de potássio na cultura da soja

The tropical soils, usually poor in potassium (K), demand potassium fertilization when cultivated with soybean (Glycine max L.) to obtain satisfactory yields. The aim of this study was to evaluate the effects of K doses and soil humidity levels on soybean agronomic characteristics. The experiment was carried out in a greenhouse, in pots with two plants, containing 5 dm3 of soil. The experimental design was completely randomized block with treatments in a 5 x 3 factorial arrangement. The K doses were 0; 30; 60, 120 and 180 mg dm-3, and the soil humidity ranged from 35 to 40; 47.5 to 52.5; and 60 to 65% of the total porosity. The characteristics appraised were: grain yield, weight of a hundred grains, total number of grains per pot, K level in the grain, number of viable pods. There was soybean response to the potassium fertilization, with increase of the grain yield, mass of a hundred grains, K level in the grain and number of viable pods. The grain total per pot reached maximum value in combination of the upper limits of each study factor. The K reduced the water deficit effects on the soybean.

Minimum number of common bean plants per plot to assess field resistance to white mold

ABSTRACT This study aimed to determine the minimum number of plants per plot to assess the field resistance in common bean to white mold. Thirteen cultivars were inoculated with six isolates of Sclerotinia sclerotiorum and evaluated in a randomized block design with three replications and plots consisting of 1-m rows with 15 plants. Plants were inoculated by the straw test as proposed by Petzoldt and Dickson (1996), to evaluate partial resistance in a greenhouse. Eight days after inoculation the disease severity was evaluated on a 1-9 diagrammatic scale, where 1 = asymptomatic plants to 9 = plant death. To determine the minimum number of plants per plot, the following methods were used: maximum curvature, segmented linear model, quadratic segmented model and the relative CV model. There were significant differences among cultivars and isolates and no significant cultivar - isolate interaction. It was observed that eight plants per plot is an adequate number to assess the reaction of common bean to white mold.

Comparison of macro-morphological and physiological methods for Monilinia species identification in Paraná State, Brazil

Abstract The aim of this study was to characterize 93 isolates of Monilinia from stone fruit orchards of Paraná State Brazil, and make inferences concerning their physiological aspects. A synoptic key was utilized at 10 days after incubation for morphological characterization, which allowed us to identify three Monilinia species (M. laxa, M. fructigena and M. fructicola). Molecular analysis was later performed for isolates representative of the morphological species. The polymerase chain reaction (PCR) confirmed only M. fructicola to be present for all isolates collected in Paraná State and contradicted the synoptic key identification. Additionally, isolates were tested physiologically in order to support Monilinia segregation. However, no significant differences were found among the isolates for optimum growth temperature and lesion size of inoculated pear fruit. We concluded that the synoptic key cannot segregate isolates of Monilinia species from southern Brazil and that PCR with specific primers was the best approach.

Comparative in vivo and in vitro study on Monilia fructicola causing brown rot of stone fruit in Brazil and California

Stone fruit production plays an important economical role in southern Brazil as well as in California, United States. In both countries, brown rot caused by Monilinia fructicola is the most important stone fruit disease, responsible for significant pre- and post-harvest fruit losses. The United States is among the main importers of stone fruit to Brazil. Imported fruit carrying the pathogen may introduce isolates with greater ability to infect stone fruit orchards in Brazil. In this study, 26 M. fructicola isolates from Brazil and California, recovered from commercial stone fruit orchards, were randomly selected and compared based on in vitro (optimum growth temperature, mycelial growth rate, germination, spore production and germ tube rate) and in vivo (sporulation, area under disease progress curve, incubation and latent period) studies on brown rot infection components. The isolates behaved similarly for most of the studied variables, except for germ tube length and sporulation on fruit, which were higher in isolates from California and Brazil, respectively. The negative correlation between these variables may be disadvantage for isolates from California to cause infections in the main peach cultivar grown in South Brazil. Significant differences in incubation and latent period and the area under disease progress curve were found among isolates from a same country. Such differences may be due to intraspecific diversity associated with the occurrence of the perfect stage in California, and by the broad sampling area from where isolates from Brazil were obtained. It is still difficult to determine the effect of isolates arising from imported California fruits in Brazilian stone fruit orchards. Further genetic variability studies and comparative epidemiology in the field may help to understant the real threat that foreign isolates represent.

Comparison of the sensitivity of Monilinia fructicola isolates to tebuconazole in Brazil using three methods

Abstract The frequency of strains of Monilinia fructicola that are resistant to the demethylation inhibiting fungicide tebuconazole in Brazil was determined by three methods. The first involved testing 295 isolates for relative growth under a discriminatory dose of 0.3 µg mL−1. The second and the third methods involved testing 120 isolates for the effective concentration for 50% population inhibition (EC50); one method employed the discriminatory dose of 0.3 µg mL−1 and the other method utilized the baseline dose of 0.046 µg mL−1 to separate the strains based on sensitivity. The frequencies of resistance among the isolates based on the three methods were determined by measuring mycelial growth in fungicide-amended media. The shifts in M. fructicola sensitivities were determined by comparing the EC50 density distributions of the baseline (2000–2004, n=31), intermediate (2005–2008, n=88), and current (2009–2011, n=120) isolate populations. The frequency of resistance to tebuconazole varied according to the assessment method; the resistance frequencies were 18.3% for the relative growth method, 40% for the baseline EC50 method, and 8.33% for the EC50 method segregated by the dose of 0.3 µg mL−1. The application of the EC50 method involving the discriminatory dose of 0.3 µg mL−1 revealed a decrease in the frequency of resistant genotypes. However, the baseline EC50 method is recommended for future resistance surveys because this method was originally used to determine the mean sensitivity prior to the use of tebuconazole in Brazil. Additionally, a shift of the current population toward sensitivity was observed compared with the intermediate population. Finally, São Paulo was found to be the state with the highest EC50 values (0.186 µg mL−1) compared with Paraná (0.053 µg mL−1) and Rio Grande do Sul (0.026 µg mL−1). These results suggest that the build-up of fungicide resistance in Monilinia fructicola has been prevented by the use of anti-resistance strategies in the main peach production areas of Brazil; however, additional studies are required to demonstrate how resistance instability and fitness are affecting isolate sensitivity.