Population dynamics of rice nematodes under a system of rice intensification

Abstract

Field experiments were conducted for two consecutive growth seasons to study the dynamics of the populations of the rice root nematode, Hirschmanniella oryzae, and the rice root-knot nematode, Meloidogyne graminicola, infecting rice under a System of Rice Intensification (SRI) in comparison with a conventional lowland irrigated cultivation system. Population densities of H. oryzae and M. graminicola were markedly influenced by the two different rice cultivation systems. In the soil, the populations of H. oryzae increased significantly by harvest of the second season in the conventional lowland cultivation system, but remained at low levels under SRI, while the populations of M. graminicola increased greatly under SRI and were low in the conventional system. In the roots, H. oryzae populations increased greatly in both seasons and peaked at harvest, while M. graminicola remained at rather low levels throughout the two seasons. The grain yield was significantly larger in SRI plots than in conventional irrigated rice plots in both seasons, by 33.3% in the first season but only 18.5% in the second season.