Crop rotation with <i>Brassica</i> reduces disease in potato crops

Abstract

A longterm trial (5 years) was conducted at a commercial property with a history of high incidence and severity of soilborne diseases Five rotational crops (potato pasture Brassica cereal and squash) were tested for their effects on soilborne diseases on potatoes These crops were grown in plots for about 4 months and then ploughed back into the soil 30 days prior to planting potatoes Soil applications of metalaxyl fungicide were used as a standard (control) treatment After four growing seasons there was evidence that rotational treatments particularly Treatment 2 (cereal Brassica crop) reduced the amount of diseased potatoes and the proportion of the crop that was diseased compared with the control treatment (potatoes and pasture with or without metalaxyl) (P0046 and 0016 respectively) Combining these results with harvest data from previous years there was no significant difference between the treatments in terms of yield per plant However there did appear to be a marginal difference (P01) in the proportion of the crop that was diseased with Treatment 4 (without Brassica crop) being higher than other treatments that had Brassica crops In previous work soil analysis had shown that a rotation with Brassica crops reduced the level of Phytophthora and other species of soilborne fungi compared with the same rotation without Brassica crops