ABSTRACT
Soybean is considered one of the most important crops for agribusiness in Brazil. Surveys of plant parasitic populations constitute an important tool to detect the presence of nematodes and losses. This study aimed to use geostatistics as a tool to check the spatial variability of Meloidogyne javanica in two soybean crops, one of which presented plants with symptoms characteristic of nematode parasitism and the other area had plants without symptoms. The study was conducted in the city of Araruna, Paraná State, and both areas were cultivated with soybean cultivars BMX Power RR. Soil and root were collected by following irregular grid of 50 georeferenced points. To check and estimate the degree of spatial dependence among the populations, geostatistical analysis was used. After adjusting the variogram, kriging and sequentially the spatial distribution map of nematodes in the areas were obtained. The whole geostatistical process was carried out with the computer program GS +. Only at four points, nematodes were detected in soil samples and at low population level; thus, such data were not analyzed by means of geostatistics. In the area presenting yellowish plants reduced in size, the presence of M. javanica was detected in 60% of the samples, where the obtained population ranged from 0 to 70,992 nematodes in 10g root, with an average of 3,807. The variogram fit to the spherical model, with a range of 30.80 m and spatial dependence of 86%; then, the collection of nine subsamples would be required to satisfactorily represent a hectare. In the area where plants with visible symptoms were not observed, 38% of the samples had M. javanica and at low population level. The obtained population ranged from 0 to 2,184 nematodes in 10g root, with an average of 262. The obtained range was 11.60 m, with spatial dependence of 99% and fitting to the Gaussian model, since in this case the collection of 74 subsamples would be required for satisfactory representation of a hectare. The geostatistical analysis was efficient for spatial distribution studies of plant parasitic nematodes.
Keywords
horizontal distribution; knot-root; geostatistics
