Effect of short-term growth of mung bean and its incorporation with nitrogen fertiliser on the density of the root-knot nematode, Meloidogyne incognita, in soil

Soybean is attacked by multiple plant-parasitic nematodes and the major ones are soybean cyst nematode (SCN) and root-knot nematodes. Our previous study reported that 2 weeks growth of mung bean and its soil incorporation markedly reduced SCN density in soil via hatching stimulation by mung bean residue. This study aimed: i) to evaluate whether incorporation of mung bean in combination with N fertiliser decreased the density of Meloidogyne incognita, which attacks both soybean and mung bean; and ii) to determine the direct effect of ammonium solutions on M. incognita J2 and hatching. The results showed that after the growth period of mung bean for 2 weeks and 4 weeks of its incorporation, the density of M. incognita was significantly reduced by 54 and 72% in the mung bean treatment with and without N fertiliser (140 mg N (kg soil)(-1)), respectively, compared with the control. Soil urease activity was significantly higher in the mung bean with N fertiliser than in the control. Meloidogyne incognita second-stage juveniles were less mobile in NH4Cl solutions with 100-250 mg N l(-1) than in 0 mg N l(-1). Moreover, NH4Cl solutions with 140 mg N l(-1) and 250 mg N l(-1) significantly inhibited the hatching of M. incognita. This study demonstrated that 2 weeks growth of mung bean may be a potential trap crop for M. incognita and N metabolism might be involved to a certain extent in the suppression of M. incognita.