Abstract The present study aimed to investigate the response of soybean cultivars with different susceptibility levels to the root-knot nematode Meloidogyne javanica at varied time intervals by analyzing the initial plant–nematode interaction using antioxidant enzymes as oxidative stress markers. A 4 × 4 × 2 factorial method with 5 repetitions was used to analyze 4 soybean cultivars at 4 different collection times—6, 12, 24, and 48 h—with and without M. javanica inoculation. The parameters evaluated were the activities of antioxidant enzymes phenol peroxidase (POX) and ascorbate peroxidase (APX); the concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA); and the number of M. javanica juveniles penetrated into each plant. H2O2 concentration varied among the cultivars with and without inoculation and at different collection times as indicated by MDA concentration and POX and APX activities, demonstrating a rapid response of the host to an infection by M. javanica. Oxidative stress caused by M. javanica did not vary among the soybean cultivars regardless of their susceptibility level; however, the antioxidant enzymes POX and APX responded according to the susceptibility level of the cultivars. rootknot root knot plantnematode plant markers times6, times6 6, 6 times—6 12 24 hwith h M (POX (APX) HO H O (H2O2 (MDA) H2O however times— 1 (APX (H2O (MDA

A análise do efeito da profundidade de semeadura e carga vertical visando a melhorar o aproveitamento, e a integração entre o solo e a cultura é muito difícil. O objetivo do presente trabalho foi avaliar cargas verticais (0; 98; 196 e 294 N) sobre as rodas compactadoras das semeadoras, combinando com profundidades de semeadura (0,03; 0,05 e 0,07 m) para a cultura da soja. O trabalho foi realizado no DER/UNESP - Jaboticabal, na pista de ensaio do Laboratório de Máquinas e Mecanização Agrícola (LAMMA), utilizando o delineamento experimental em blocos casualizados, no esquema fatorial (4 x 3), com 12 tratamentos e três repetições, totalizando 36 observações. Foram analisados: emergência de plântulas, estandes inicial e final, índice de sobrevivência, área mobilizada e rendimento de grãos. Os resultados evidenciaram que, com exceção da área mobilizada em relação à profundidade de semeadura, todas as demais variáveis não foram influenciadas pelos tratamentos.

The choice of a soil tillage system, aiming the best use and integration between soil and crop, is very difficult. The objective of the present work was to evaluate vertical loads (0; 98; 196 and 294 N) on the press wheels of the seeders working at sowing depths (0.03; 0.05 and 0.07 m) for the soybean. The work was carried out at Rural Engineering Department of UNESP - São Paulo State University, Jaboticabal, Brazil, in the Machines and Mechanization Laboratory’s area. The experiment design was 4x3 factorial in randomized blocks with three replications, totalling 12 treatments and 36 observations. The emergence, initial and final population of cultivation, index of surving plants, immobilized area in sowing and the yield grain were analyzed. The results showed that, except for mobilized area concerning the working depth of sowing shaft, all the other variables were not influenced by the treatments.