Soil mineral N dynamics beneath mixtures of leaves from legume and fruit trees in Central Amazonian multi-strata agroforests

Long term applications of leguminous green mulch could increase mineralizable nitrogen (N) beneath cupuaçu trees produced on the infertile acidic Ultisols and Oxisols of the Amazon Basin. However, low quality standing cupuaçu litter could interfere with green mulch N release and soil N mineralization. This study compared mineral N, total N, and microbial biomass N beneath cupuaçu trees grown in two different agroforestry systems, north of Manaus, Brazil, following seven years of different green mulch application rates. To test for net interactions between green mulch and cupuaçu litter, dried gliricidia and inga leaves were mixed with senescent cupuaçu leaves, surface applied to an Oxisol soil, and incubated in a greenhouse for 162 days. Leaf decomposition, N release and soil N mineralization were periodically measured in the mixed species litter treatments and compared to single species applications. The effect of legume biomass and cupuaçu litter on soil mineral N was additive implying that recommendations for green mulch applications to cupuaçu trees can be based on N dynamics of individual green mulch species. Results demonstrated that residue quality, not quantity, was the dominant factor affecting the rate of N release from leaves and soil N mineralization in a controlled environment. In the field, complex N cycling and other factors, including soil fauna, roots, and microclimatic effects, had a stronger influence on available soil N than residue quality.

Soil CO2 efflux in central Amazonia: environmental and methodological effects

Soil respiration plays a significant role in the carbon cycle of Amazonian rainforests. Measurements of soil respiration have only been carried out in few places in the Amazon. This study investigated the effects of the method of ring insertion in the soil as well as of rainfall and spatial distribution on CO2 emission in the central Amazon region. The ring insertion effect increased the soil emission about 13-20% for sandy and loamy soils during the firsts 4-7 hours, respectively. After rainfall events below 2 mm, the soil respiration did not change, but for rainfall greater than 3 mm, after 2 hours there was a decrease in soil temperature and respiration of about 10-34% for the loamy and sand soils, with emissions returning to normal after around 15-18 hours. The size of the measurement areas and the spatial distribution of soil respiration were better estimated using the Shuttle Radar Topographic Mission (SRTM) data. The Campina reserve is a mosaic of bare soil, stunted heath forest-SHF and tall heath forest-THF. The estimated total average CO2 emissions from the area was 3.08±0.8 µmol CO2 m-2 s-1. The Cuieiras reserve is another mosaic of plateau, slope, Campinarana and riparian forests and the total average emission from the area was 3.82±0.76 µmol CO2 m-2 s-1. We also found that the main control factor of the soil respiration was soil temperature, with 90% explained by regression analysis. Automated soil respiration datasets are a good tool to improve the technique and increase the reliability of measurements to allow a better understanding of all possible factors driven by soil respiration processes.

Chemical and physical attributes and calcium, magnesium, potassium, and phosphorus in the soil of murundu fields in Brazil

Fields of murundus (FM) are wetlands that provide numerous ecosystem services. The objectives of this study were to evaluate the chemical [organic carbon (OC), P, K+, Ca2+, Mg2+, Al3+ and H+Al] and physical [texture and bulk density (Bd)] soil attributes and calculate the organic matter (OM) and nutrient stock (P, Ca, Mg, and K) in soils of FM located in the Guapore River basin in Mato Grosso. Thirty-six sampling points were selected, and soil samples were collected from two environments: the murundu and plain area surrounding (PAS). At each sampling point, mini trenches of 0.5 × 0.5 × 0.4 m were opened and disturbed and undisturbed soil samples were collected at depths of 0-0.1, 0.1-0.2, and 0.2-0.4 m. In the Principal Component Analysis the variables H+Al (49%) and OM (4%) were associated with the F1 component and sand content (47%) with the F2 component. The FM had lower pH values and higher concentrations of K+, P, and H+Al than PAS at all depths (p < 0.05). Additionally, FM stocked up to 433, 360, 205, and 11 kg ha-1 of Ca, Mg, K, and P, respectively, for up to a depth of 0.2 m. The murundu stored two times more K and three times more P than that in the PAS. Our results show that the FM has high sand content and Bd greater than 1.5 Mg m-3, high acidity, low OC content, and low nutrient concentrations. Thus, special care must be taken to preserve FM such that human intervention does not trigger environmental imbalances.

Process of fixation, imobilization and mineralization of ammonium in soil using N-15

The organic and inorganic forms of soil nitrogen and how they participate in the process of fixation, immobilization and mineralization of ammonium in soils were evaluated, after different periods of incubaton, utilizing two soils, a Lithic Haplustoll and a Typic Eutrorthox. The results obtained permit to suggest that : 1) The method for determination of the ammonium fixing capacity based on the extraction with 2N KC1, is considered to be subject to interferences of other soil fractions capable of retaining ammonium. 2) The increase in exchangeable ammonium content is related to the decrease in amino acids and hydrolyzable ammonium. 3) The immobilization and mineralization processes are still held under mil microbial. The forms more affected by this condition are amino acids and hydrolyzable ammonium.

Doses and methods of distribution of potassium chloride on soybean crop (Glycine max (L.) Merrill) in a red latosol, affecting soil salinity, grain production and chemical composition of leaves

The present work deal t wi th an experiment under field conditions and a laboratory test of soil incubation the objectives were as follows: a. to study effects on soybean grain product ion and leaf composition of increasing doses of potassium chloride applied into the soil through two methods of distribution; b. to observe chemical modifications in the soils incubated with increasing doses of potassium chloride; and, c. to correlate field effects with chemical alterations observed in the incubation test, The field experiment was carried out in a Red Latosol (Haplustox) with soybean cultivar UFV - 1. Potassium chloride was distributed through two methods: banded (5 cm below and 5 cm aside of the seed line) and broadcasted and plowed-down. Doses used were: 0; 50; 100 and 200 kg/ha of K2O. Foliar samples were taken at flowering stage. Incubation test were made in plastic bags with 2 kg of air dried fine soil, taken from the arable layer of the field experiment, with the following doses of KC1 p,a. : 0; 50; 100; 200; 400; 800; 1,600; 3.200; 6,400 and 12,800 kg/ha of K(2)0. In the conditions observed during the present work, results allowed the following conclusions: A response by soybean grain production for doses of potassium chloride, applied in both ways, banded or broadcasted, was not observed. Leaf analysis did not show treatment influence over the leaf contents for N, P, K, Ca, Mg, and CI, Potassium chloride salinity effects in both methods of distribution for all the tested closes were not observed.

Increasing the efficiency of utilization of soil and fertilizer phosphorus in the subtropical and tropical agricultural systems C

As a rule, soils of the subtropical and tropical regions, in which rainfall is not limiting, are acidic, and low in phosphorus, and, to a less extent, in other macro and micronutrients as well, such a sulfur, boron and zinc. The establishment of a permanent agricultural prac. tice therefore, demands relatively high usage of liming and phosphatic fertilization, to begin with. Several approaches, not mutually exclusive, could be used in order to increase the efficiency of utilization of soil and fertilizer phosphorus so that, goal of diminishing costs of production is reached. The use of liming materials bringing up pH to 6.0-6.5 causes the conversion of iron and aluminum phosphates to more available calcium phosphates; on the other hand, by raising calcium saturation in the exchange complex, it improves the development and operation if the root system which allows c or a higher utilization of all soil nutrients, including phosphorus, and helps of stand water deficits which may occur. The role of mycorrhizal fungi should be considered as a way of increasing soil and fertilizer P utilization, as well as the limitations thereof. Screening of and breeding for varieties with higher efficiency of uptake and utilization of soil and fertilizer phosphorus leads to a reduction in cost of inputs and to higher benefit/cost ratios. Corrective fertilization using ground rock phosphate helps to saturate the fixation power of the soil thereby reducing, as a consequence, the need for phosphorus in the maintenance fertilization. Maintenance fertilization, in which soluble phos-phatic sources are used, could be improved by several means whose performance has been proved: limimg, granula tion, placement, use of magnesium salts. Last, cost of phosphate fertilization could be further reduced, without impairing yields, through impairing yields, through changes in technology designed to obtain products better adapted to local conditions and to the availability or raw materials and energy sources.

Soil invertebrates in southern Brazilian Araucaria forest - grassland mosaic: differences between disturbed and undisturbed areas

Soil invertebrate distribution in Araucaria forest, grassland and edge habitats was studied in both disturbed and undisturbed areas in southern Brazil. Mean-density and taxa compositions were verified. Invertebrate densities differed between grassland and the other two habitats in the undisturbed area but not across the disturbed one. At the disturbed area taxa differed between the grassland and the other two habitats. The undisturbed area, on the other hand, presented taxa differences only between the grassland and the forest habitats. Acari, Arachnida and Collembola were the most sensitive taxa for detecting differences across habitats in both areas. At the disturbed area, these taxa presented densities lowering from the forest to the grassland. At the undisturbed area the same taxa increased from the forest to the grassland. Coleoptera and Formicidae (Insecta) presented no difference between habitats at the studied taxonomic level.

Estudos dos agrupamentos vegetativos relacionados com as áreas onde foram efetuadas as pesquisas sôbre a febre amarela silvestre no Município de Passos, Estado de Minas Gerais

The work reported here was carried-out on the invitation of Dr. Henry Kumm, Director of the Rockefeller Foundation, and by appointment from Dr. Henrique Aragão, Director of the Instituto Oswaldo Cruz. It was done during the investigation of sylvan yellow fever, in June 1947, with a view to establishing the phyto-ecological conditions of the county of Passos. The pe¬riod was, however, too short for definite conclusions to be reached. Thanks are due to Dr. O. R. Causey, Chief of Research on Yellow Fever for transpor¬tation and other help. THE REGIONAL VEGETATION. Aerial photographs of the county of Passos shoto that it is covered by three great types of vegetation: Rain Forest, Secondary Pasture Land and Scrub.1 Detailed investigation, however, brings out the fact that these correspond to different seres; furthermore, each type presents not only the specific, characteristics of the biological form dominant for the climate, but also are at various stages, which express HABITATS differing from those of the normal sere. The phytogeographic survey of the region shows that most of it is now covered by secondary pasture land (disclimax) in which Melinis minutiflora, v. "fat grass" (fig. 1), predominates. The mosaic of Rain Forest and of small patches of Scrub reveals the effects of human intervention (BARRETO, H. L. de Mello 1); consequently, all the formations have to be regarded as secon¬dary, though some of them probably include relicts of the primitive climax (WARMING, E. 2). On close examination, the Scrub cannot be considered as the climax, because of the following facts: 1. In the zone of Rain-Forest stretches of forest are present in very varied topographic conditions and the reconstitution of the associations show that man has destroyed an ecological unit (fig. 2). 2. In the zone of Scrub the characteristic patches are small. The banks of rivers and brooks, the valleys and ravine and whatever the soil has retained some humidity, is being invaded fry Rain Forest, which seems to be growing under optimum conditions. The Scrub is thus limited to small belts on the calcareous mountains and on sandy soils with alcaline depths (pH abo¬ve 7) which do not retain enough moisture for the Rain Forest that is progres¬sively restricting the area occupied by Scrub. In view of the topographic and present climatic conditions the Rain Forest must consequently be regarded as the regional climax. The presence of ecologically contradictory elements and associations shows that the real problem is that of the fluctuations of the climate of Passos or even of Minas Geraes during the quaternary and recent periods (DAN-SEREAU, P. : 3), a subject on which little is known and which is tied to the evolution of the climate of Brazil (OLIVEIRA, E. : 4) . The transformation of Scrub into Rain Forest has been - observed by the author before, in other parts of Brazil (VELOSO, PL P.: 5) . It seems probable that the Rio Grande has also greatly influenced the change of the regional vegetation, by invading areas of Scrub and dislocating the limit of the Pluvial climate towards the Canastra Range, though there are remnants of Scrub (postclimax) transfor¬med into secondary open country (disclimax, fig. 5) by human devastation and the setting of fire to the land. VEGETATION GROUPS OF THE PLUVIAL TYPE. The map of the region also shows that at the present time the small patches of forest (whether devasted or intact) occupy the least accessible places, such as valleys, peaks and abrupt slopes (fig. 2). Even these are now being destroyed, so that in the near future this forested region will be en¬tirely reduced to poor pasture land unless energetic measures of conservation are undertaken in time. The Special Service for Prophylaxis against Yellow Fever installed two of their four Stations for the Capture of Mosquitos in this area, one of them at Batatal and the other at Cachoeira, which have separate formations each of them composed of several associations. Other vegetation formations were also analysed, from the synecological point of view, so as to ascertain of which degree of succession their associations belong. These phytosociological sur¬veys give an idea of the principal characteristics of each station. BATATAL FORMATION. The abrupt nature of the valley has rendered this location inappropriate for agricultural purposes since colonial times. The relict of the primitive forest climax saved by this circumstance has expanded gradually to zones whose paedologic conditions favour the eatablishment of mesophilous species. The aerial photograph shows two small stretches of forest, one apparently primi¬tive, the other composed of associations belonging to the subclimax of the subsere. CACHOEIRA FORMATION. Aerial photographs show that this station is crossed by a small river, which divides it into two separate parts. The first, which presents ecological conditions similar, though not identical to those of Batatal, is favoured by topography and apparently remains primitive forest. Though the topography of the other, on the whole, favours the establishment of groups belonging to the normal sere of the climax, is has been partly devastated recently and the aspect of the associations has been completely modified. It was is this part that the four posts for the capturing of mosquitos were set up. The first forest is favoured by deposition of organic matter, washed out from the nearby devasted areas by torrential rains, and thus provides, an appropriate HABITAT for the climax species with certain hygrophilous trends of the ecological quasiclimax type. This association seems to have reached a biological equilibrium, as the dominates. Gallesia gorarema and Cariniana legalis (fig. 10), present an optimum vitality with a vigorous habit and a normal evolutionary cycle. The Cariniantum legalis Gallesiosum equilibrium, corresponds however, to a provisory association, because if the moving of soil by torrential rains should cease it would become possible…

The isolation of the perfect form of Microsporum Gypseum, Nannizzia Gypsea, Stockdale, 1963, from brazilian soil

Our work is on the isolation from brazilian soil of the perfect stage of Microsporum gypseum, Nannizzia gypsea, Stock., 1963, using cut sterilized children hair as bait.

Outbreak of human toxoplasmosis in a rural area. A three year serologic follow-up study

Thirty-six persons living on a farm located in the state of Minas Gerais (Brazil) were studied. Nine of them had the glandular form of toxoplasmosis, between May and August, 1976. These nine cases of toxoplasmosis were confirmed serologically by immunefluorescence-IF-, presenting IgG antibody titres between 1:4096 and 1:32000 and IgM antibody titres between 1:16 and 1:8000. Twelve out of thirty-six persons studied were considered to be "dubious cases". They were defined either by presenting a clinical picture compatible with acquired toxoplasmosis, yet having low serologic titres, or inversely they did not have a clear clinical picture but had serologic evidence of recent Toxoplasma infection. Fifteen out of thirty-six persons studied showed neither serologic nor clinical evidence of recent Toxoplasma infection. The epidemiologic information suggests two possible modes of transmission: a) poorly cooked pork at a barbecue party; b) farm vegetables and soil contaminated with Toxoplasma gondii oocysts (rat-cat cycle). Serologic follow-up nine months later in the human farm population demonstrated still high IgG titres, yet they tended to decline and IgM titres became negative. Three years later most of the IgG titres continued to decline and were almost compatible with the titres obtained in Brazilian population surveys.