Marcelo de Carvalho Alves

Application of the Köppen classification for climatic zoning in the state of Minas Gerais, Brazil

The knowledge of the climatic conditions of a region is crucial for its agricultural development. It is also extremely important for understanding the fact that certain cultures have to develop under prevailing temperature and humidity conditions and assist in the adoption of a suitable irrigation technique, as well as its management and operationalization. The Köppen system of climate classification is widely used for the identification of homogeneous climate zones as it considers only rainfall and temperature as the meteorological elements for classification. For this study, we used climatic databases of rainfall and temperature in a raster format, with a spatial resolution of 30″ of arc (an approximate area of 0.86 km2 pixel−1), from 1961 to 1990. Through geoprocessing techniques, we obtained a map of climatic classification for the state of Minas Gerais. We found that the state has the following three major climatic groups: A, B and C, which correspond to tropical rainy, dry and warm temperate climates, respectively. The climate classes obtained were Aw, Am, BSh, Cwa and Cwb, with Aw, Cwa and Cwb classes occupying 99.89% of the territorial area of the state. The validation of the results showed a satisfactory agreement, with 93.75% reliability.

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

The recent and widespread expansion of the pioneer tree species Vochysia divergens Pohl into western Brazil has the potential to significantly alter the structure and function of the Pantanal—a UNESCO World Heritage Site and the World’s largest tropical wetland. Here we assess the seasonal pattern of evapotranspiration (ET) and micrometeorological variables of V. divergens (locally known as cambarazal), located in the Northeast of the Brazilian Pantanal. ET was calculated from a number of micrometeorological measurements recorded between January 2007 and January 2008. The results indicate that ET was the dominant sink for net radiation (Rn) during the wet and dry seasons, primarily because the forest was either flooded (December–May) or retained a high level of soil moisture. ET decreased during the dry season due to a decline in Rn and surface water availability, and an increase in atmospheric vapor pressure deficit. Based on this analysis we conclude that the spread of V. divergens into the Pantanal and the associated high rates of ET are due in part to high water availability, even during the dry season, and the consistently high leaf area index that increases the transpiration surface area when the water table is below the soil surface.

Scanning Electron Microscopy for Fungal Sample Examination

This chapter presents general and specific methods for preparing fungi, plant, and seed tissues infected with fungi, and nematodes parasited by fungi using scanning electron microscopy (SEM). Conventional methods with chemical fixation as well as cryofixation are included, with details for subsequent steps of sample preparation to get optimal fungal specimens for visualization and examination through SEM.

Geostatistical analysis of fruit yield and detachment force in coffee

The aim of this study was to use geostatistical analysis to evaluate the spatial variation in the detachment force of coffee fruit and coffee yield by variograms and kriging for precision agriculture. This study was conducted at Brejão farm, Três Pontas, Minas Gerais, Brazil. The detachment force of green and mature coffee fruit was measured with a prototype dynamometer and georeferenced. The yield data were obtained from manual harvesting and were georeferenced. The data were evaluated by variograms estimated by residual maximum likelihood (REML), which provided a satisfactory approach for modeling all the variables with a small sample size. Spherical and exponential models were fitted, the first provided the better fit to mature fruit detachment force and the latter provided the better fit to coffee yield and green fruit detachment force. They were used to describe the structure and magnitude of spatial variation in the variables studied. Kriged estimates were obtained with the best fitting variogram models and mapped. The statistical and geostatistical analyses enabled us to characterize the spatial variation of the detachment force of green and mature coffee fruit and coffee yield and to visualize the spatial relations among these variables. The precision agriculture techniques used in this paper to collect, map and analyze the variables studied will help coffee farmers to manage their fields. Maps of coffee yield will enable farmers to apply nutrients site-specifically and manage harvesting either manually or mechanically. In addition, maps of detachment force of coffee fruit can enable farmers to harvest coffee selectively by choosing the appropriate places and the right time to start. This will improve the quality of the final product and also increase profits.

Uso da restrição hídrica na inoculação de fungos em sementes de algodoeiro (Gossypium hirsutum)

Availability of seeds infected by fungi or other transmissible pathogens by this way is extremely important in seed pathology for several purposes. The present research was conducted to evaluate the use of the water restriction technique in the inoculation of cotton seeds in order to obtain seeds infected by Colletotrichum gossypii, Colletotrichum gossypii var. cephalosporioides, Botryodiplodia theobromae and Fusarium oxysporum f. sp. vasinfectum. The premise was based on the fact that seed infection is better ensured and controlled by keeping the seeds in contact with the developing fungal colonies on agar media containing mannitol at osmotic potentials that would arrest seed germination for a longer period of time. In this study mannitol was tested at the potentials of 0, -0.4, -0.6, -0.8 e -1 MPa. Seeds on the fungal colonies were placed in a growth room at 25oC, with a photoperiod of 12 hours, where they remained for different periods of time, according to the water potential used. After each incubation period seeds were taken out of the media and dried out on paper towels in a lab environment and submitted to the germination, emergence and health tests. Incubation of seeds at water potential ranging from -0.8 to -1 MPa, provided conditions to impede seeds from germinating for a period of up to 4 and 5 days, respectively, and then presenting a greater level of infection and higher percentages of diseased seedlings.

Adaptive neuro-fuzzy inference systems for epidemiological analysis of soybean rust

The objective of this work was to develop and to evaluate adaptive neuro-fuzzy inference systems as methodology to describe the severity of soybean rust (Phakopsora pachyrhizi) monocyclic process in soybean Glycine max (L.) Merr.], under effects of leaf wetness, temperature, and days after fungi inoculation. The experiment was conducted in growth chambers with mean air temperatures of 15, 20, 25 and 30?C and leaf wetness periods of 6, 12, 18 and 24h. The plants were inoculated by spraying a suspension of P.?pachyrhizi inoculum at concentration of 104 uredinosporemL-1. A disease assessment key was adopted for estimate amounts of soybean rust at 0, 6, 9, 12 and 15 days after fungi inoculation. A hybrid neural network training with 3 and 3000 epochs was applied to disease severity data for optimization of fuzzy system parameters used to describe the severity of soybean rust based on leaf wetness, temperature and days after fungi inoculation. Higher accuracy and precision of the neuro-fuzzy systems estimates were obtained after training with 3000 epochs. Nevertheless, training with 3 epochs produced smoother estimates. The neuro-fuzzy systems enabled to describe the severity of soybean rust monocyclic process under effects of leaf wetness, mean air temperature and days after fungi inoculation and was better applied for Conquista cultivar, followed by Savana and Suprema cultivars. Higher soybean rust severity was verified under temperatures among 20?C and 25?C, leaf wetness above 6h, with higher values above 10h, and 15 days after fungi inoculation. Temperatures near 15?C increased the latent period of the disease but not inhibited its development after 10 days of fungi inoculation.

Efeitos da colheita manual na bienalidade do cafeeiro em Ijaci, Minas Gerais

Analisou-se, neste trabalho, a relacao entre a produtividade e a desfolha do cafeeiro durante o processo de colheita manual nas safras agricolas de 2005, 2006 e 2007. O experimento foi desenvolvido na fazenda Cafua, localizada no municipio de Ijaci, sul de Minas Gerais, em uma area de 6,5ha de lavoura de cafeeiro (Coffea arabica L.) da variedade cultivada Catuai Vermelho IAC-99. Foi demarcada na area uma malha irregular na distância de 25x25 e 50x50m, num total de 67 pontos amostrais, nos quais foram avaliados a producao de cafe (L.planta-1) obtida por meio da colheita no pano e a desfolha das plantas, quantificada com base no peso de folhas (kg. planta-1) apos a colheita manual. Procedeu-se a analise de correlacao de Pearson para verificar a relacao linear entre a produtividade e a desfolha nos diferentes periodos avaliados. A dependencia espacial dos dados tambem foi analisada por meio de ajustes de semivariogramas e interpolacao por krigagem. Constatou-se que a colheita manual desfolhou mais em locais de maior produtividade, e apresentou reducao da produtividade de cafe na lavoura no ano subsequente, pelo aumento da desfolha em plantas de maior produtividade e consequente reducao da radiacao fotossinteticamente ativa interceptada pelo dossel dessas plantas, ocasionando bienalidade da producao.

Geostatistical improvements of evapotranspiration spatial information using satellite land surface and weather stations data

The objective of the present study was to use the simple cokriging methodology to characterize the spatial variability of Penman–Monteith reference evapotranspiration and Thornthwaite potential evapotranspiration methods based on Moderate Resolution Imaging Spetroradiometer (MODIS) global evapotranspiration products and high-resolution surfaces of WordClim temperature and precipitation data. The climatic element data referred to 39 National Institute of Meteorology climatic stations located in Minas Gerais state, Brazil and surrounding states. The use of geostatistics and simple cokriging technique enabled the characterization of the spatial variability of the evapotranspiration providing uncertainty information on the spatial prediction pattern. Evapotranspiration and precipitation surfaces were implemented for the climatic classification in Minas Gerais. Multivariate geostatistical determined improvements of evapotranspiration spatial information. The regions in the south of Minas Gerais derived from the moisture index estimated with the MODIS evapotranspiration (2000–2010), presented divergence of humid conditions when compared to the moisture index derived from the simple kriged and cokriged evapotranspiration (1961–1990), indicating climate change in this region. There was stronger pattern of crossed covariance between evapotranspiration and precipitation rather than temperature, indicating that trends in precipitation could be one of the main external drivers of the evapotranspiration in Minas Gerais state, Brazil.

Variabilidade espacial e temporal do fósforo, potássio e da produtividade de uma lavoura cafeeira

The Precision Agriculture appears as an important tool to the management of coffee farms where the knowledge of some soil features associated with the coffee production could help specific application of fertilizing with positive environmental and economic results. So the aim of this study was to use precision agriculture and geoestatistics to evaluate the variables phosphorus, potassium and the coffee plant yield, in three different crops, by evaluating the semivariogram and kriging maps and show that these tools are important to the coffee management. This study was conducted on the Brejao farm in Tres Pontas, Minas Gerais, in 2007/2008, 2008/2009 e 2009/2010 crop. As data base were used chemical soil data obtained by sampling in a georreferenced location using a quadricycle with a sampler and a GPS, and the yield data was obtained from manual harvest on the georreferenced location. It was possible to characterize the spatial variability magnitude of the studied attributes, and they presented huge variation on time and space. Adjusts of the best semivariograms enable to produce more accurate maps that contribute to the geostatistics uses on coffee crop.

Scanning electron microscopy applied to seed-borne fungi examination.

The aim of this study was to test the standard scanning electron microscopy (SEM) as a potential alternative to study seed‐borne fungi in seeds, by two different conditions of blotter test and water restriction treatment. In the blotter test, seeds were subjected to conditions that enabled pathogen growth and expression, whereas the water restriction method consisted in preventing seed germination during the incubation period, resulting in the artificial inoculation of fungi. In the first condition, seeds of common bean (Phaseolus vulgaris L.), maize (Zea mays L.), and cotton (Gossypium hirsutum L.) were submitted to the standard blotter test and then prepared and observed with SEM. In the second condition, seeds of cotton (G. hirsutum), soybean (Glycine max L.), and common bean (P. vulgaris L.) were, respectively, inoculated with Colletotrichum gossypii var. cephalosporioides, Colletotrichum truncatum, and Colletotrichum lindemuthianum by the water restriction technique, followed by preparation and observation with SEM. The standard SEM methodology was adopted to prepare the specimens. Considering the seeds submitted to the blotter test, it was possible to identify Fusarium sp. on maize, C. gossypii var. cephalosporioides, and Fusarium oxysporum on cotton, Aspergillus flavus, Penicillium sp., Rhizopus sp., and Mucor sp. on common bean. Structures of C. gossypii var. cephalosporioides, C. truncatum, and C. lindemuthianum were observed in the surface of inoculated seeds. Microsc. Res. Tech., 2009.