Vânia da Silva Fraga

Propágulos de fungos micorrízicos arbusculares em solos deficientes em fósforo sob diferentes usos, da região semi-arida no nordeste do Brasil

The conversion of tropical dry forest into areas used for subsistence agriculture or livestock production is a common feature of the semi-arid region of NE Brazil. Our study looked into the effect of these land use changes on propagules of arbuscular mycorrhizal fungi (AMF) at ten sites distributed in the states of Paraiba and Pernambuco. Each site consisted of an area under native vegetation (Dry-Forest) adjacent to a cultivated area in the same slope position. Soil samples were taken at distance intervals of 20-30 m from two depths (0-7.5 and 7.5-15 cm) along a transect crossing the adjacent areas (10 sites x 2 land uses x 2 depths x 4 sampling points). Roots (< 2 mm) found in the soil samples (n = 160) were stained with trypan blue to assess the percentage of AMF colonization as well as the type of fungal structures. The AMF spores were separated from soil by wet sieving, incubated in iodonitrotetrazolium chloride (INT) solution and counted; those stained with INT were considered viable. Soil samples were analyzed for resin-extractable P and total organic carbon (TOC). For data analysis, the 10 areas under dry forest were separated in two sub-groups: Undisturbed-Dry-Forest (UDF, n = 6) and Disturbed-Dry-Forest (DDF, n = 4), owing to the different degradation degrees. Likewise, the 10 cultivated areas were also separated in two sub-groups: Preserved-Cultivated (PC, n = 4) and Degraded-Cultivated (DC, n = 6). Thus, four levels of increasing land use intensity or degradation were established, in agreement with the land use history, visual symptoms of vegetation or soil degradation, and soil erosion measured using the 137Cs technique. Effects of increasing soil degradation on AMF propagules were observed in the 0-7.5 cm layer only, except for non-viable spores. The density of viable spores varied from 1.4 to 6.8 spores/50 g soil and of non-viable spores from 91.4 to 226 spores/50 g soil. The most consistent results in relation to the effect of selective logging (thinning) on propagules were found in the DDF group which had a larger number of viable spores, more intense root colonization and a lower proportion of samples with vesicules than the other groups. Soil samples had very low concentrations of resin-extractable P (< 6 mg kg-1 soil). Root colonization was less intense in samples where the resin-extractable soil P was lower than 1.5 mg kg-1 soil than in samples with higher P concentrations. It was further observed that root colonization and the number of viable spores were favored by higher TOC concentrations.

Nodulação e fixação de nitrogênio por forrageiras da caatinga cultivadas em solos do semiárido paraibano

A fixacao biologica de nitrogenio foi avaliada em jureminha (Desmanthus pernambucanus), orelha-de-onca (Macroptilium martii) e feijao-de-rolinha (Macroptilium lathyroides) cultivados em solos do semiarido da Paraiba, em vasos sem e com esterco bovino. Foram determinados o numero e a biomassa de nodulos, os teores e as proporcoes de nitrogenio (N) fixado (percentual de nitrogenio da planta derivado do ar-%Ndda), pelo metodo da abundância natural, utilizando-se o capim-buffel como planta controle. As leguminosas tiveram nodulacao abundante, nos tres solos e na ausencia ou presenca de esterco, salvo quando cultivadas em Neossolo Fluvico sem adubacao. A adubacao com esterco aumentou o numero e a biomassa de nodulos. A fixacao biologica de nitrogenio foi alta nas tres especies, nos tres solos: na maioria das plantas, os valores superaram 50%, chegando a 85%. Esses dados permitem estimar a capacidade de fixacao das especies no campo em 10 a 30 kg ha-1 de N, considerando as densidades de plantio e produtividade usuais. As menores %Ndda e quantidades fixadas foram encontradas nas plantas cultivadas em Neossolo Regolitico e aumentaram com a adicao de esterco. Entre as especies testadas, a fixacao biologica de nitrogenio foi menos importante para D. pernambucanus. Nenhum dos parâmetros de nodulacao avaliados (numero, biomassa e biomassa/nodulo) explicou as proporcoes nem as quantidades de nitrogenio fixadas pelas plantas.

Residual effect of organic fertilization on maize yield in an agroforestry system

The objective of the present study was to evaluate, during a period of two years, the residual effects of organic fertilization with animal manure or gliridicia prunings on the fertility of soil and on productivity and nutrient accumulation by maize cultivated either isolated (SA) or intercropped within alleys of gliricidia (CA). The study was conducted during 2006 and 2007 in the Centro Agroecologico Sao Miguel, headquarters of the NGO AS-PTA, in Esperanca, PB, Brazil. The experiment was established in a split-plot design, arranged in randomized blocks, with the type of cropping system (SA or CA) as the main treatments and the organic fertilization (animal manure, gliricidia prunings or control plots) as the secondary treatments, with four replications. The organic fertilization with animal manure led to a residual effect increasing maize productivity during the two years, but the fertilization with gliricidia prunings had no residual effect. The residual effect on maize productivity was more pronounced in the SA plots, compared to the plots with gliricidia alleys (CA). Probably, the lower residual effect within the CA system was due to the competition between maize and gliricidia for resources (nutrients, water and light), which indicates the need for higher rates or more frequent fertilizer applications in these systems. The contents of P, K, Ca and Mg in the soil was higher in the plots that received animal manure within both types of cropping systems.

Cu e Zn na cultura do sorgo cultivado em três classes de solos: I. Crescimento vegetativo e produção

The micronutrients copper and zinc are important for good vegetative growth and for grain formation in cereals. An experiment was carried out aiming to evaluate the effect of copper and zinc application upon growth attributes of sorghum and upon its grain yield. A randomized block experimental design was used, with a combination of five doses of copper (0, 0.26, 0.90, 1.54 and 1.80 mg kg-1) and five doses of zinc (0, 0.32, 1.1, 1.88 and 2.2 mg kg-1) combined by Box Central Composite design, resulting in nine treatments which were applied in three soil classes (Latosol, Alfisol and Entisol), with three replications. Ninety six days after sowing, growth attributes and sorghum yield were determined. The copper application increased leaf area, stem diameter, panicle length and diameter, dry matter yield and grain yield, however the same results were not observed for zinc application. The foliar concentrations of copper and zinc presented negative interactions between the applied doses. Alfisol was the soil most influenced by nutrient application.

Biomassa e nutrição mineral de forrageiras cultivadas em solos do semiárido adubados com esterco

Biomass production and N, P and K uptake by four forage species were compared in three soils from the semi-arid region of Paraiba, with or without organic manure. The species were three legumes (Desmanthus virgatus , Macroptilium martii and Macroptilium lathyroides) and one grass (Cenchrus ciliaris); the soils, a Fluvic Neosol, a Regolithic Neosol and Haplic Planosol; and cattle manure was applied at a dose equivalent to 20 Mg ha-1. Manure application resulted in large increases in biomass production and nutrient uptake, in all species and soils. Apparently, the manure supplied enough P but not enough N and K to the plants, confirming that it is a good source of the first nutrient. Macroptilium martii and Macroptilium lathyroides seem to be the highest biomass producers, mainly in response to fertilization. Cenchrus ciliaris had higher K concentrations and contents than the legumes, indicating a larger K absorption capacity. There was no correspondence between soil analysis and nutrient supplying capacity.

Cu e Zn na cultura do sorgo cultivado em três classes de solos: II. Composição mineral

The micronutrients copper and zinc have important functions in vegeatable metabolism, but studies about micronutrient needs for sorghum are scarce. Aiming to evaluate the effect of copper and zinc application in nutritional attributes of sorghum an experiment was carried out in a randomized block experimental design with a combination of five doses of copper (0, 0.26, 0.90, 1.54 and 1.80 mg kg-1) and five doses of zinc (0, 0.32, 1.1, 1.88 and 2.2 mg kg-1) combined by Box Central Composite design, resulting in nine treatments, which were applied in three soil classes (Latosol, Alfisol and Entisol), with three replications. Ninety six days after sowing, nutrients contents and accumulation and protein contents were determined. The copper application increased nitrogen, phosphorus, potassium and copper contents and crude protein content in grains, however, the same results were not observed for zinc application. Alfisol was the soil most responsive to the application of nutrients.

Efeito de doses de boro no crescimento vegetativo de girassol em diferentes classes de solos

Effect of boron levels in vegetative growth of sunflower in different soil classes The low availability of boron (B) in the soil is one of the limiting factors for the production of sunflower , which is an oleaginous plant characterized by broad climatic adaptability . The objective of this study was to evaluate the influence of boron rates applied in different soil classes on the development of sunflower cultivar Helium 863. The samples were collected in the layer 0-20 cm of the soil classes Gray Argisol ‐ GL, Red Yellow Argisol - RYA, Litholic Neosol - LN, Eutrophic Red Argisol ‐ ERA, Fluvic Neosol - FN and Haplic Vertisol ‐ HV. The experiment was arranged in a randomized block 4 x 6 factorial (soils x doses) design, with four replications. The experimental unit was represented by one plant per pot. The soils showed significant effect (p <0.01) for all growth parameters studied. The sunflower plants grown in the soils FN, HV, GL and LN showed the highest leaf area, the lar gest inflorescence diameter, the highest levels of foliar boron, lar gest number of leaves and highest plant height, respectively . Fertilization with boron did not influence the production of dry matter of sunflower cv . Helium 863.

Eficiência de adubação de batatinha com esterco e N mineral (15N) e efeito residual no cultivo do milheto

The N content of the sandy soils in the semi-arid region of Paraiba State cultivated with potato (Solanum tuberosum) is low. Annual applications of farm manure (FM) and mineral N, determined on an empirical basis, have led to accumulation and/or loss of soil nutrients. Thus, the objective of this study was to determine the efficiency of ammonium sulphate (15N) combined with FM applied to potato as well as the residual effects on subsequent millet. A field experiment on an Alfisol compared the combination of a rate of 16 t ha-1 FM + 80 kg ha-1 of mineral N, as most frequently used in the region, with a rate of 11 t ha-1 of FM combined with 0, 40 and 80 kg ha-1 of N in single or split applications. The ammonium sulphate was enriched in 15N (2.5 % 15N abundance). The dry weight of potato and millet aboveground mass was determined in all treatments, as well as the N isotopic composition of both materials. Fertilization at the traditional rate proved to be excessive for this soil, since crop yields were not reduced when the rates were reduced to 11 t ha-1 manure + 40 kg ha-1 mineral N. However, yields were lower with applications of manure alone. Millet recovered much of the mineral N added to potato and was a good alternative for forage production in the area.