Mechanisms of nematode suppression in inundated amended waste soil contaminated wiht potato cyst nematodes Globodera rostochiensis and G. pallida

Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida are a significant threat to potato production. PCN can persist in soil for long periods of time and is easily spreadby farm machinery, waste soil and residues from potato processing industries. Inundation is receiving more attention as an alternative to soil fumigants for disinfestation of waste soil. Weinvestigated if agricultural and industrial waste products accelerate the disinfestation process in inundated conditions by studyingPCN survival over time, as well as the mechanisms ofthis observed nematode suppression. Experiments were conducted in 2-L closed containers filled with 1.5 L non-amended soil (1), or soil amended with (2) steamed potato peels, (3) fresh potato peels, or (4) green top parts of leek. In each container, 25 cysts of G. rostochiensis or G. pallidawere buried in the soil in retrievable nylon mesh bags and 400 ml tap water was added.The viability, hatching and infectivity of the eggs and juveniles retrieved from the containers as well as concentrations of volatile fatty acids (VFA) and gases (O2, CO2, H2S, CH4, and N2) weredetermined 14, 17, 21, 24 and 28 days after inundation. After 28 days, inundation of non-amended soil caused 50% reduction inPCN survival while in amended soil survival was reduced up to 99.5%. Hatching and infectivity of juveniles were reduced one week after inundation in amendedsoil compared with non-amended inundated soil. Higher concentrations of VFA and carbon dioxide and lower levels of oxygen were detected in amended treatments. Hydrogen sulphide was occasionally detected in the leek amended treatment. Our study showed that application of amendments improved the effect of inundation as a disinfestation practice and that depletion of oxygen and generation of H2Sbut also formation of acetic, butyric and propionic acids are involved in nematode suppression.