Efeito da época e da profundidade de coleta do solo e raiz da soja na quantificação da população de Meloidogyne incognita

Abstract

Soybean (Glycine max) is one of the most cultivated crops in the world. Brazil has become the largest producer producing milions of tons in almost 37 milion hectares. However, production ends up being limited by phytosanitary problems, maany of them caused by phytonematodes. The root-knot nematodes (Meloidogyne spp) are very harmful in world agriculture, as they habe a wide geographic distribuition and few control methods. Above all a ccorrect identification and sampling of these phytonematodes in the field facilitates na effective control. However there are disagreements among aauthors regarding recommendations regarding the spatial and temporal distribuition of nematodes in the field. Thues the following work aims to evaluate the best planting time and the best collection depth to quantfy the population of M. incognita. To carry out the studies, collections were made in a plot infested with M incógnita at theree points within the reboleira. The collection was stratifield dividing the soil around theree plants in layers of depths 0 to 10cm, soon after 10 to 20 cm and 20 to 30 cm. In each 10 cm layer, 700 grams of soil and all available roots were removed. Samples were collecteed at diferente reproductive stages, starting at R1 and following at R3, R5.1, R5.3 and R6. The nematode extractions took place in the laboratory using the Jenkins method (1964) to extract the nematode in the soil and Coolen & D’Herde (1972) to extract the nematode in the root. The analysis of variance was submitted by the F test and the means of the variables were compared by the Tukey test at 5% probability. The variables under evaluation were: root mass, population of M. incognita in thee roots and populatio of M incognita in the soil. The time of collection influenced only the population of M incognita in the root, and the depth influenced both the amount of root mass and the population of M incognita in the root. The significance of these two factors occurred independently. It is therefore concluded that the best planting time for collecting and sampling the soil is at the R5.3 phenological stage and the best collection depth is 0 to 10 cm.