Effect of soil fumigation on white clover growth in a yellow‐grey earth infested with clover cyst nematode

A field trial to study the effects of soil fumigants on pure swards of ‘Grasslands Huia’ white clover growing in a yellow‐grey earth infested with clover cyst nematode (Heterodera irijolii), was run for 18 months. The treatments, replicated four times (24 plots, 2 × 1 m), were: control, methyl bromide, ‘DD’ soil fumigant at 300 l/ha, ‘Nemagon’ at 11.23 l/ha. ‘Nemagon’ at 22.46 l/ha, and ‘Mocap’ at 67 kg/ha.Twelve harvests were made during the trial and mean yield response to fumigation was 7.6%–0.2%(‘Nemagon’ 22.46 l/ha) to 12.3% (‘D.D.’). However, during periods of activity of the clover cyst nematode yields were up to 46% higher in fumigated than in control plots.The effect was enhanced by moisture stress. Fumigation also extended the growing season into the summer drought.