Sandra Cátia Pereira Uchôa

Gênese, química e mineralogia de solos derivados de sedimentos pliopleistocênicos e de rochas vulcânicas básicas em Roraima, Norte Amazônico

The influence of parent material, varying from Plio-Pleistocene sediments and basic volcanics, and topographic position, to soil genesis, was studied in a topolitossequence typical of savanna at the Cauame River catchment, Roraima. We aimed to describe the soil variability under savanna by means of chemical, physical and mineralogical attributes. Fourteen soil profiles were described and samples, allowing the identification of the following classes: Yellow Latosol, Red Latosol, Yellow and Red-Yellow Argisols, Plinthosols, Gleisols, Fluvic Neosols and Vertisols. The mineralogy was determined by DRX. The pedogenetical processes and soil characteristics were closely related with topographical-hydrological variation and underlying lithology. Soils derived from pre-weathered sediments of the Boa Vista Formation are generally of low fertility, with high acidity and kaolinite mineralogy and low Fe-oxides contents. Soils developed from Basalt or under the influence of alluvia with mafic contribution all showed high base saturation (eutric) and clay mineralogy with the presence of 2:1 clays, with varying amounts of kaolinite. The occurrence of Vertisols, degraded carbonatic nodules and eutric soils under savanna indicate Quaternary drier paleoclimates in this part of north Amazonia, during which carbonates were formed in the lower horizons of Vertisols, in closed depressions.

Resposta do feijão-caupi à doses e formas de aplicação de fósforo em Latossolo Amarelo do Estado de Roraima

Phosphorus fertilization and ways of phosphate fertilizers application are important factors considering crop management. This study aimed at assessing the effect of phosphorus rates and phosphate fertilizers application forms on growth and phosphorus uptake of cowpea plants cropped on cerrado soil in the State of Roraima, Brazil. An experiment took place under field conditions, on a Yellow Latosol, at Cauame Campus of Roraimas Federal University, located in the municipality of Boa Vista/RR. The experimental design was split-plot, in a completely randomized blocks, with three replicates. The plots consisted of the following phosphoric fertilizers application forms: a) broadcasting; b) single furrow and c) double furrow. Sub-plots corresponded to phosphorus doses: 0, 0,5; 1,0; 1,5, and 2,0 times the recommended dose for cowpea maintenance fertilization (60 kg ha-1 of P2O5). There was a significant effect of P rates over plant growth and plant uptake. Application of fertilizer in double furrows promoted higher plant growth, grain yield, and plant phosphorous uptake.

Doses de basalto moído nas propriedades químicas de um latossolo amarelo distrófico da savana de Roraima

Basaltic rocks have chemical and mineralogical composition that allows its agricultural application due to its capability of improving soil fertility. The aim in this work was to evaluate the effect of levels of finely crushed basalt rock in soil chemical conditioning. A dystrophic Yellow Latosol from pre-weathered Boa Vista Formation was used. The rock of the Apoteri formation was collected in the mine of Nova Olinda near Boa Vista. The treatments consisted of the incorporation and incubation of eight rock powder levels (0; 0.85; 1.70; 3.35; 5.03; 10.05; 20.40 and 40.80 g kg-1). The experimental design was entirely randomly with eight treatments and three replicates. After the incorporation of the rushed rock powder for a period 180 days of soil incubation, the soil was analyzed and determined the values of Ca2+, Mg2+, pH in H2O, pH in KCl, Al3+, H+ Al, Zn, Fe, Cu and Mn. The level of 20.40 g kg-1 of basalt provided the maxim reduction of the active acidity, varying from 4.8 to 5.5. Concentrations of exchangeable Ca2+ and Mg2+ increased, but their increments in the soil solution was small. Basalt levels presented high efficiency for neutralization of the potential acidity. Amendments with crushed rock increased extractable amounts of Zn, Fe and Cu in soil, after incubation.

SOLOS DA ÁREA INDÍGENA YANOMAMI NO MÉDIO RIO CATRIMANI, RORAIMA

Em Roraima, a distribuicao espacial das populacoes indigenas identifica um cenario de busca constante de solos capazes de sustentar uma agricultura itinerante. Este trabalho teve como objetivo estabelecer relacao entre a compreensao dos solos por parte dos Yanomami da regiao do medio Catrimani e o Sistema Brasileiro de Classificacao de Solos, bem como avaliar o seu tipo de uso em funcao de analises quimicas para diagnostico da fertilidade do solo. O trabalho foi executado em duas etapas. A primeira consistiu em visitas a oito malocas para estudar os solos. Foram coletadas amostras em trincheiras ate 1,50 m de profundidade para analise e classificacao dos solos e (em prospeccoes com o trado) nas profundidades de 0-10 a 10-30 cm, em 21 tipos de uso agricola, e da area de floresta para analises quimicas de fertilidade. A segunda fase foi uma oficina, abordando os sistemas de exploracao agricola, com duracao de 20 h. Focalizou-se a discussao sobre a compreensao do meio ambiente (Urihi)(1) e sistemas de producao agricolas e sobre a importância do uso correto do conhecimento dos solos. Os solos sao denominados pelos Yanomami em funcao das caracteristicas morfologicas, pelos teores de materia orgânica e pela presenca de minhocas, e da posicao na paisagem - a escolha para agricultura e fundamentada nessas caracteristicas. As praticas agricolas consistem da derrubada da mata nativa, queima e plantio das culturas em separado. Os solos descritos na area foram: Argissolo Vermelho-Amarelo (Maxita a uuxi wake axi), Argissolo Amarelo (Maxita a axi), Latossolo Amarelo (Maxita a axi) e Plintossolo (Maxita a axi a maamaxipe). O processo de derruba e queima promove um incremento inicial do teor de Ca e K trocaveis e P assimilavel devido a contribuicao das cinzas, o que permite a exploracao das areas por um periodo maximo de tres anos.In Roraima, the spatial distribution of indigenous peoples indicates a background of constant search for soils capable of sustaining shift cultivation. This study aimed to establish a relationship between the understanding of soil by the Yanomami tribe from the mid-Catrimani river region and the Brazilian System of Soil Classification and evaluate the type of agricultural land use according to soil fertility tests, in two steps. The first consisted of visiting eight Indian communities to collect soil samples at 21 sites with different types of agriculture and forests, both from profile soil (depth 0-1.50 m) and pits (depth 0-0.1 m and 0.1-0.3 m) for laboratory analysis. The second step was a workshop addressing the shift cultivation systems (duration 20 h). The discussion focused on the understanding of the environment (Urihi) and agricultural production systems, and on the importance of the correct use of knowledge of the soil and its fertility. Soils are named according to their morphology and position in the landscape by the Yanomami. The choice of agricultural areas is based on these features, aside from the organic matter content and the presence of earthworms. Agricultural practices comprise clearing and burning of the native forest immediately before planting a set of separate crops. The soils described in the area were classified according to the Brazilian taxonomic system as follows: Red Yellow Argisol (Maxita a uuxi wake axi), Yellow Argisol (Maxita a axi) Yellow Latosol (Maxita a axi) and Plintosol (Maxita a axi a maaxipe). Slashing and burning initially increases exchangeable Ca, K and available P due to the contribution of the ashes, which allows an agricultural exploitation of these areas for a maximum period of three years.

Efeito da aplicação de pó de basalto no desenvolvimento inicial de mudas de camu-camu (Myrciaria dubia)

The seedling production of native fruits is an important step towards the preservation of species, commercial exploitation and sustainable employment generation. In this context, alternative fertilizers, such as rock dust, provide obtaining a substrate with higher fertility, nutrient-rich, with reduced costs in manpower and replacement of fertilization. The objective in the present research was to evaluate the initial development of camu-camu seedlings (Myrciaria dubia H.B.K. McVaugh) in function of levels of crushed basalt. The experiment was carried out in a greenhouse, at CCA/UFRR. The experimental designed was completely randomized with eight treatments and five repetitions in factorial scheme (5x2+1), being five levels of crushed basalt (0, 0.42, 1.04, 2.08, 4.17 and 8.33 g kg-1), two particle size (0.05 mm and 0.10 mm f). Vases of polyethylene of 14L of capacity were the experimental units, and the soil was a Distrofic Yellow Latosol. The incubation period of the soil in vases was for 120 days and after that period the seedlings were transplanted to vases. Six months after the transplant the height, diameter of plant, branches number, and aerial part and root dry biomass of seedlings were determined. From this data the morphologic indexes were calculated. The Treatments without crushed basalt (0 g kg-1) and the levels 0.42 g kg-1 produced seedlings of lower quality in both granulometry analyzed. The better development of seedlings of camu-camu was obtained using 4.17 e 8.33 g kg-1 of crushed basalt with 0.05 granulometry.

Método de determinação de enxofre lábil com membrana de troca aniônica

The availability of S in soils can be understood by the interplay among the intensity factor, quantity factor and soil S buffering capacity. The quantity factor is the labile nutrient pool, defined as the quantity present in the soil solid phase, capable of dissolving into the soil solution during one growing cycle of a given annual crop. Aiming to develop a quantification method for labile S, three soils samples were incubated for 60 days after the following treatments: (a) non-disinfected sample, and no S added (-D, -S); disinfected sample, and no S added (+D, -S); non-disinfected sample with S added (-D, +S); disinfected sample with S added (+D, +S). For the labile S determination, 50 x 20 mm of Cl-saturated anionexchange membranes were used. In order to define the labile S determination method, three assays were carried out as follows: (1) extraction with a different number of anion-exchange membranes; (2) successive extractions every 16 h, with one anion-exchange membrane, and (3) extractions at different shaking times (1, 2, 4, 8, 16, 24, 36, 48 and 72 h). Results indicate that the continuous shaking for 48 h and extraction with a single anion-exchange membrane is a feasible and efficient method, extracting a greater proportion of labile S, henceforth termed readily labile sulphur (RLS). The sulphur amount extracted between 48 and 152 h was called slowly labile sulphur (SLS), whereas the not extracted amount of sulphur after 152 h of shaking was labeled non-labile pool (NLS).

Doses de enxofre e tempo de incubação na dinâmica de formas de enxofre no solo

A disponibilidade de enxofre (S) depende da dinâmica de suas formas no solo. Visando estudar o equilibrio entre as reservas de S labil e S nao labil, amostras de 10 solos foram incubadas com cinco doses de sulfato de calcio (0, 20, 50, 80 e 120 mg dm-3 de S), durante 1, 8, 15, 30, 60 e 90 d. Para a determinacao do S labil, utilizou-se membrana de resina de troca anionica em forma de lâmina. O S extraido com 48 h de agitacao foi denominado de enxofre rapidamente labil (SRL). O teor obtido com tempo de agitacao superior a 48 h foi denominado de enxofre lentamente labil e o nao labil (SLL+SNL), pela diferenca entre o S do solo (extraido apos calcinacao) e SRL. A resistencia que o solo oferece a passagem do S da reserva do SRL para a do SLL+SNL foi denominada de capacidade-tampao do S labil (CTSL), sendo obtida pelo inverso do coeficiente angular das equacoes lineares do teor de SRL em funcao do teor de SLL+SNL. Constatou-se que tempo de incubacao (reatividade) e as doses de S, na forma de sulfato de calcio, influenciam a dinâmica do S entre as reservas de SRL e SLL+SNL. A CTSL e sensivel as mudancas no equilibrio entre as reservas de S no solo. O aumento da CTSL dos solos relacionou-se, principalmente, com a capacidade maxima de adsorcao de sulfato, teor de carbono orgânico, goethita e gibbsita da fracao argila dos solos estudados.

Avaliação da fixação biológica de nitrogênio em feijão-caupi submetido a diferentes manejos da vegetação natural na savana de Roraima.

Objetivou-se com este trabalho avaliar a fixacao biologica de nitrogenio em feijao-caupi submetido a diferentes manejos da vegetacao natural, com e sem adubacao orgânica com esterco bovino, da savana de Roraima. O experimento foi instalado na area experimental do CCA/UFRR, em Boa Vista, Roraima. O plantio das sementes de feijao-caupi, cultivar BRS Arace, inoculadas com Bradyrhizobium BR 3262, foi realizado em julho de 2011 e os tratamentos foram dispostos em um delineamento experimental de blocos ao acaso em esquema fatorial (3 x 2) com quatro repeticoes. O primeiro fator correspondeu ao manejo da vegetacao natural: com aplicacao de glifosato, com corte da vegetacao natural e sem corte da vegetacao natural. O segundo fator correspondeu a aplicacao de esterco bovino: com e sem aplicacao. Aos 35 dias apos o plantio foi efetuada a coleta das plantas de feijao-caupi para mensurar o numero de nodulos; massa fresca e seca dos nodulos; altura da planta; numero de folhas, massa fresca e seca da parte aerea; massa fresca e seca da raiz. A aplicacao a lanco de esterco bovino na quantidade de 2,0 L m-2 sobre a vegetacao natural da savana de Roraima favorece o aumento do numero de nodulos por planta de feijao-caupi. O manejo da vegetacao natural com o uso do glifosato, independentemente do uso do esterco, favorece a nodulacao das raizes e contribui com o maior crescimento e desenvolvimento da planta de feijao-caupi.

Ácido cianídrico em tecidos de mandioca em função da idade da planta e adubação nitrogenada

O objetivo deste trabalho foi avaliar o teor de acido cianidrico em tecidos de mandioca, em funcao da idade da planta e niveis de adubacao nitrogenada. Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo de parcelas subdivididas, com quatro repeticoes. As doses de nitrogenio em cobertura (0, 30, 60, 150 e 330 kg ha -1 ) foram alocadas nas parcelas, e as epocas de avaliacao (90, 120, 150, 180, 240, 300 e 360 dias apos o plantio), nas subparcelas. Os teores de acido cianidrico foram avaliados em tecidos da folha, caule, polpa e cortex da raiz da cultivar Aciolina. Os efeitos das doses de N e das epocas de avaliacao foram independentes. Doses entre 219 e 241 kg ha -1 de N em cobertura proporcionam os maiores teores de acido cianidrico, que variaram de 332 a 401 mg kg -1 de materia fresca nos tecidos avaliados. O teor de acido cianidrico nos tecidos reduz-se linearmente com a idade da planta. O cortex da raiz acumula o maior teor de acido cianidrico, e a polpa da raiz o menor. Por ocasiao da colheita, aos 360 dias apos o plantio, essa cultivare classificada como mandioca mansa.