Grasses and legumes as cover crop in no-tillage system in northeastern Pará Brazil

Studies to select one or more species of coverage plants adapted to Amazonian soil and climate conditions of the Amazon are a promising strategy for the improvement of environmental quality, establishing no-till agricultural systems, and thereby reducing the impacts of monoculture farming. The aim of this study was to assess the persistence time, half-life time, macronutrient content and accumulation, and C:N ratio of straw coverage in a Ultisol in northeastern Pará. Experimental design was randomized blocks with five treatments and five replicates. Plants were harvested after 105 days, growth and biomass production was quantified. After 84 days, soil coverage was 97, 85, 52, 50, and 15% for signalgrass (Brachiaria brizantha) (syn. Urochloa), dense crowngrass (Panicum purpurascens), jack bean (Canavalia ensiformes), pearl millet (Pennisetum americanum) and sunn hemp (Crotalaria juncea,), respectively. Signalgrass yielded the greatest dry matter production (9,696 kg ha-1). It also had high C:N ratio (38.4), long half-life (86.5 days) and a high persistence in the field. Jack bean also showed high dry matter production (8,950 kg ha-1), but it had low C:N ratio (17.4) and lower half-life time (39 days) than the grasses. These attributes indicate that signalgrass and jack bean have a high potential for use as cover plants in no-till agricultural systems in the State of Pará.

Effect of day time on foliar spraying of several levels of nitrogen fertilizer, NPKS solutions and its components, on common bean leaves

An experiment was carried out in order to determine the effect of day time of foliar spraying of several levels of nitrogen fertilizers, N-P-K-S station, and its components on common bean leaves. Results, based on the visual observations, indicated the maximum levels of each fertilizer that did not cause injuries and showed that the foliar spraying early in the morning is the best day time.

Effects of foliar fertilization of common bean (Phaseolus vulgaris, L.) during the seed-filling stage

An experiment was carried out with common bean (Phaseolus vulgaris, L.) in a Red Yellow Latossol, sandy phase, in order to study the influence of foliar spraying of the Hanway nutrient solution (NPKS) at grain filling stage on: 1) grain yield; 2) the uptake of fertilizer and soil nitrogen by this crop through the root system and 3) the efficiency of utilization of the nitrogen in the foliar spray solution by the grain. The results of this experiment showed that the foliar application of the Hanway solution with ammonium nitrate at the pod filling period caused severe leaf burn and grain yield was inferior to that of the plants which received a soil application of this fertilizer at the same stage. These facts can be attributed to the presence of ammonium nitrate in the concentration used. The composition of final spray was: 114,28 Kg NH4NO3 + 43,11 Kg potassium poliphosphate + 12,44 Kg potassium sulphate per 500 litres. The uptake of nitrogen fertilizer through the root system and the efficiency of its utilization was greater than that through the leaves.

Accumulation of micronutrients by sweet sorghum under field conditions

Samples of two cultivars of sweet sorghum (Brandes and Rio) grown on a Dark Red Latosol (Latossolo Roxo, Barra Bonita, SP.) were collected at intervals of 20 days during their life cycle and the contents of micronutrients were determined by routine procedures. Usually the physiological stages in which the rate of absorption was higher were not the same for both varieties.

Influence of boron on growth and mineral composition of bean (Phaseolus vulgaris L.)

Nine cultivars of Phaseolus vulgaris L. were grown in nutrient solution to study the effect of boron on growth and mineral composition. Data obtained in thie study allowed for the following conclusions: (1) high levels of boron affected plant height, root length, dry weight of tops, dry weight of root, and total dry weight; (2) regression analysis was used to point out differential behaviour among cultivars in relation to boron concentration in nutrient solution; (3) the best mineral concentration in the plant tissue was obtained with application of 0,5 ppm of boron in the nutrient solution.

Influence of aluminum on growth and mineral composition of bean (Phaseolus vulgaris L.)

Seven cultivars of Phaseolus vulgaris L. were grown in nutrient solution in the presence and absence of aluminum. Da ta obtained herewith allowed for the following conclusions to be drawn: (1) plant height, root lenght and total dry weight decreased with increase of aluminum levels in the nutrient solution; (2) aluminum concentration in plant tissue increased with higher levels of aluminum in the substrate; decreases pf calcium and magnesium concentration in the dry matter in the presence of higher aluminum concentration in the nutrient solution were observed.

New field observations on the competitive displacement between two species of planorbid snails inhabiting Northeastern Brasil

Observations reported in the present paper have shown that Biomphalaria glabrata is being gradually displaced by B. straminea in coastal areas of two counties on the state of Pernambuco, Brazil, confirming former observations made in the same region.

What is paragonimus rudis (diesing, 1850)?: report on a field study in Mato Grosso, Brazil

Paragonimus rudis was found in the lungs of a giant otter Lutra (pteronura) brasiliensis by Natterer in 1828, who dissected the animal in the former capital Mato Grosso (=Vila Bela), Brazil. The flukes were described by Diesing in 1850, and redescribed by Braun in 1901. Both descriptions do not allow to identify the species. Therefore, P. rudis must be regarded a "nomen nudum". Because its rediscovery is desirable with regard to historical reasons and nomenclatoric questions, a field study was performed in Mato Grosso in 1980. Of 354 freshwater crabs from 24 localities collected and examined for parasitic infections, about 25% were found to be infected with 7kinds of trematode larvae, which differed distincly from Paragonimus-metacercariae. The question, whether P. rudis or other lung fluke species do not seem to occur or cannot be found any longer in the area investigated by us, is discussed.

Methods for field detection of resistance to temephos in simuliids. Larval esterase level and topical application of the insecticide to adults

Two practical field methods for indirect detection of simuliid populations resistant to temephos are proposed. The first is based on high esterase activity in resistant larvae and involves adaptations of a filter paper test in which faintly stained spots indicate susceptible populations and strongly stained ones reveal populations resistant to temephos. The second is based on the resistance to the larvicide when adults are topically exposed, and involves the use of diagnostic doses obtained by the comparison between the LD50 for susceptible and resistant populations. The relevance of such methods is discussed in order to help resistance detection in Simulium pertinax Kollar control programmes.

Preliminary laboratory and field trials of a heated pheromone trap for the sandfly lutzomyia logipalpis (Diptera: Psychodidae)

A heated pheromone trap for the sandfly Lutzomyia longipalpis was tested in the laboratory using filter paper or plastic vial dispensers. Male pheromone extracted from 8 male tergal glands and absorbed on to filter paper dispensers attracted 82/120 (68.3%) of virgin females released in cages. Similarly plastic vial dispensers baited with the extract of 24 males caught 73/120 (61%). In field trials carried out near januária, Minas Gerais, Brazil using the plastic dispensers baited with extracts of 50 male tergal glands only 70 female L. longipalpis were captured. Over 1000 male flies were, however, caught during 6 nights, with greater numbers in the unbaited control traps than in the pheromone baited test traps. It is concluded that at excessive concentrations male L. longipalpis pheromone may act as a repellent to conspecific males.

Use of glass beads and CF 11 cellulose for removal of leukocytes from malaria-infected human blood in field settings

Passage of malaria infected blood through a two-layered column composed of acid-washed glass beads and CF 11 cellulose removes white cells from parasitized blood. However, because use of glass beads and CF 11 cellulose requires filtration of infected blood separately through these two resins and the addition of ADP, the procedure is time-consuming and may be inapropriate for use in the field, especially when large numbers of blood samples are to be treated. Our modification of this process yields parasitized cells free of contaminating leukocytes, and because of its operational simplicity, large numbers of blood samples can be processed. Our procedure also compares well with those using expensive commercial Sepacell resins in its ability to separate leukocytes from whole blood. As a test of usefulness in molecular biologic investigations, the parasites obtained from the blood of malaria-infected patients using the modified procedure yield genomic DNA whose single copy gene, the circumsporozite gene, efficiently amplifies by polymerase chain reaction.

Field evaluation of an exoantigen-containing Babesia vaccine in Venezuela

Bovine babesiosis is endemic in Venezuela, causing significant losses in highly susceptible imported cattle. Current immunoprphylatic methods include the less desirable use of live parasites. Inactivated vaccines derived from exoantigen-containing supernatant fluids of in vitro Babesia bovis and B. bigemina cultures have been developed and constitute a major improvement in vaccine safety, stability and ease of handling. Vaccination trials conducted under field conditions provide the final evaluation of a culture-derived B. bovis-B. bigemina vaccine. During a 5-year period, approximately 8,000 cattle were vaccinated and 16 clinical trials carried out in. 7 states of Venezuela Clinical, serologic and parasitologic data were collected monthly from 10% of the animals over a 2-year period. Data were also collected from a similar number of nonvaccinated control cattle. Analysis of results from these trials demonstrated a reduction in the incidence of clinical disease among vaccinated animals and complete protection against mortality among vaccinated and nonvaccinated cattle. Use of this inactivated vaccine offers the best combination od safety, potency and efficacy for thew immunoprophylatic control of bovine babesiosis.

Transmission blocking immunity as observed in a feeder system and serological reactivity to Pfs 48/45 and Pfs230 in field sera

Monoclonal antibodies (mAbs) and human sera from gametocyte carriers were applied in the bio-assay to test for their transmission-blocking capacity. Competition ELISA's have been developed for the detection of natural transmission blocking antibodies. Approximately 55 of the sera blocking in the bio-assay gave positive results in these competition ELISA's.