The effect of soil pH on yield losses caused by the potato cyst nematodeGlobodera pallida

Summary The effect of soil pH on yield losses due to potato cyst nematodes (Globodera pallida) was investigated in experiments in the field and in a semi-controlled environment. Through annually liming a reclaimed peat soil with about 22% organic matter, plots with pH levels of 4.5, 5.0, 5.5, 6.0 and 6.5 were obtained. In 1990 potato yields in these plots decreased from 45 t/ha at pH 4.5 to 33 t/ha at pH 6.5, whereas the nematode densitites decreased from about 18 to 9 juveniles per g soil. In a container experiment a strong interaction was recorded between soil pH and the presence of nematodes. Tuber yields were about 11% lower at pH 6.5 than at pH 4.5 in the absence of nematodes, but about 44% lower when an initial population of 27 juveniles per g soil was present.