Effects of application of sulphur dust in controlling mildew in Cashew

Cashew nut, a major cash crop of Tanzania, is mainly produced in the South Eastern part of the country. Sulphur dust is widely used for controlling powdery mildew disease caused by Oidium anacardii Noack. This can cause acidification of soils and thus, may threaten the productivity of cashew and its intercrops. To evaluate the extent and magnitude of the current acidification, pH of topsoil (0-10 cm) subsoil (10-20 cm) and (20-30) of the NARI farms where sulphur had been applied for up to 5 years was compared to other non-cashew farms. On average topsoil pH of sulphur dusted fields was 5.7, subsoil pH was 5.4. However, coefficient of variation for soil pH and sulphur in the soil were 5.3% and 78.3% respectively indicating that sulphur application do differ significantly with the soil pH hence does not influence the change in pH of the soils applied with the sulphur dust. This is due to present of sulphur powder observed in applied cashew fields indicating that the mineralization and oxidation of sulphur was too slow.