Sugarcane plays an important socio-economic role in northeastern Brazil. However, the low yield in this region is associated with several factors (e.g. frequent occurrence of plant-parasitic nematodes). In order to observe the influence of soil organic matter on the nematodes, this study aimed to characterize the spatial nematode distribution in a sugarcane field. The study was carried out in Goiana -Pernambuco State (Brazil), fifty days after sugarcane cutting (10 days after vinasse application). The sampling scheme consisted of a regular 60 × 50-m grid, 10 m spaced, through 0 to 0.2 m depth. Spatial distribution was evaluated by semivariograms fit and performed by ordinary kriging interpolation for mapping. Exponential and spherical models promoted the best fit to semivariograms, resulting in ranges from 16 to 19 m. There was a strong negative correlation between soil organic matter and plantparasitic nematode population density. Free-living nematodes had a similar distribution pattern as soil organic matter content. These results indicated that soil organic matter had important effects on spatial distribution of both plant-parasitic and free-living nematodes. Key words: Soil microfauna. Semivariogram. Spatial variability. Vinasse. ResumoA cana-de-açúcar desempenha importante papel socioeconômico para o Nordeste Brasileiro. Por outro lado, a baixa produtividade nesta região está associada a diversos fatores, dentre estes, a relevante presença de nematoides fitoparasitas. A fim de verificar a influência da matéria orgânica sobre os nematoides, o objetivo deste estudo foi caracterizar a distribuição espacial da matéria orgânica e da nematofauna em área cultivada com cana-de-açúcar fertirrigada com vinhaça. O estudo foi realizado no município de Goiana, Zona da Mata Norte de Pernambuco, 50 dias após corte da cana (10 dias após aplicação da vinhaça). Utilizou-se um sistema de amostragem em malha regular de 60 × 50 m, com espaçamento de 10 m, na profundidade de 0-0,2 m. A distribuição espacial foi avaliada por meio de ajustes de semivariogramas e realizada interpolação por krigagem ordinária para mapeamento. O modelo esférico e o exponencial proporcionaram melhor ajuste aos semivariogramas, com alcances de 16 a 19 m. A matéria orgânica correlacionou-se negativamente com a população dos nematoides fitoparasitas. O mapeamento permitiu observar padrões de distribuição espacial similares entre as comunidades de nematoides de vida livre e a matéria orgânica. Esses resultados indicam que a matéria orgânica tem um papel importante na distribuição espacial dos nematoides fitoparasitas e de vida livre. Palavras-chave: Microfauna do solo. Semivariograma. Variabilidade espacial. Vinhaça.

Nematodes present high potential as a biological indicator of soil quality. In this work, it was evaluated relations between soil physical properties and nematode community under sugarcane cropping and remaining of Atlantic Forest areas in Northeastern Pernambuco, Brazil. Soil samples were collected from September to November 2009 along two 200-m transects in both remaining of Atlantic Forest and sugarcane field at deeps of 0-10, 10-20, 20-30, 30-40, and 40-50 cm. For soil characterization, it was carried out analysis of soil size, water content, total porosity, bulk density, and particle density. The level of soil mechanical resistance was evaluated through a digital penetrometer. Nematodes were extracted per 300 cm(3) of soil through centrifugal flotation in sucrose being quantified, classified according trophic habit, and identified in level of genus or family. Data were analyzed using Pearson correlation at 5% of probability. Geostatistical analysis showed that the penetration resistance, water content, total porosity, and bulk density on both forest and cultivated area exhibited spatial dependence at the sampled scale, and their experimental semivariograms were fitted to spherical and exponential models. In forest area, the ectoparasites and free-living nematodes exhibited spherical model. In sugarcane field, the soil nematodes exhibited pure nugget effect. Pratylenchus sp. and Helicotylenchus sp. were prevalent in sugarcane field, but in forest, there was prevalence of Dorylaimidae and Rhabditidae. Total amount of nematode did not differ between environments; however, community trophic structure in forest presented prevalence of free-living nematodes: omnivores followed by bacterial-feeding soil nematodes, while plant-feeding nematodes were prevalent in sugarcane field. The nematode diversity was higher in the remaining of Atlantic Forest. However, the soil mechanical resistance was higher under sugarcane cropping, affecting more directly the free-living nematodes; especially Dorylaimidae which was the most sensible to changes in soil physical properties.

The root-lesion nematode Pratylenchus spp. causes a high-severity disease, promoting high economic losses in various crops of agricultural importance. The nematode control is difficult, especially after introduction into the area. Studies on the migration of this parasite in the soil are scarce. However, understanding nematode behavior in the soil is fundamental to increase the efficiency of management practices, especially in irrigated agriculture. This study aimed to evaluate the influence of water flow and plant stimulus on Pratylenchus coffeae mobility in segmented soil columns. The columns were segmented into 11 rings of 1 cm long filled with washed sand, one of the ends exposed to a bait, and submitted to flows of 0, 3, 7 cm3/min of water. Baits for nematode attraction and repelling consisted of sectioned tubers of yam (Dioscorea cayennensis) and cut leaves of neem (Azadirachta indica), respectively, and the absence of baits as the control. Nematodes were injected into the central segment of the column, and migration and presence in water leaching were determined five days after soil infestation. Mobility of P. coffeae varied with water flow and bait type. In the absence of water flow, nematodes migrated in the opposite direction to the neem baits, but migration was well distributed in the presence of yam baits, with specimens present in all column segments. The nematode had significantly higher resistance to water flow of 3 cm3/min in the presence of yam baits. No nematodes were found in the water leached at flows of 3 and 7 cm3/min in the absence of bait. Key words: Azadirachta indica. Dioscorea cayennensis. Lesion nematode. Soil dispersion.

Objetivou-se, fundamentando-se em índices de comunidade e razões entre grupos tróficos de nematoides, descrever a estrutura da nematofauna associada ao cultivo comercial de mamoeiro em três áreas com histórico de meloidoginose, no estado da Paraíba. Paralelamente, procurou-se estabelecer relações entre desenvolvimento das plantas, através do diâmetro do caule e a densidade populacional de nematoides fitoparasitos presentes no solo. Em cada área tomou-se um quadrilátero de 5.776 m 2 que foi subdividido em 400 (20 × 20) quadriláteros contíguos de 14,44 m 2 (3,8 × 3,8 m), com três plantas por quadrilátero. Nas áreas 1 e 3 ocorreu predominância de fitoparasitos, respectivamente de 43,85 e 39,95 % do total de nematoides encontrados, destacando-se o gênero Rotylenchulus. Na área 2, Meloidogyne foi o taxon de maior dominância entre os fitoparasitos. Nas três áreas os índices de maturidade (MI) e maturidade modificada (MMI) foram altos (> 30 %) e o índice de parasitos de plantas (PPI) variou de 20,95 a 32,88 %. Não foram encontrados modelos matemáticos que descrevessem relações entre o diâmetro do caule das plantas e as densidades populacionais dos fitoparasitos presentes no solo.