Soils
Most soils in the Dandaragan area are classified as sand, varying from coarse sands with low clay (<4%) and silt (<0.05%) content to soils with higher clay (>8%), silt (>5%) and fine sand (>16%) content. Coarse soils have lower water-holding or field capacity and may require more frequent irrigation than finer textured soils.
Variation in soil texture may affect fertiliser requirements but soil testing is used to ascertain the nutrient status of the soil before planting. Use plant testing to evaluate the effectiveness of the fertiliser program on the growing crop.
Potatoes generally tolerate low soil pH but if pHw (in water) is less than 5.5 soil and plant aluminium levels may increase and limit yield. Soil pH should be adjusted with limes such as dolomite or lime sand. Soil pH can influence the level of potato scab diseases so if amendments are needed, manage them to prevent increase in scab risk. Only apply enough lime to increase soil pHw to 6.0. Soil pH measured in CaCl2 rather than water is on average 0.8 of a unit lower than the pHw values.
Paddock selection
Potatoes can be produced on a wide range of soils but avoid waterlogged, compacted, saline or rocky/gravelly soils. Rocky or gravelly soils are difficult to till and cropping these soils may result in bruising of tubers during harvest. The Mid West has large areas of well drained soils with low EC (1:5 H2O<13mS/m or 0.13dS/m) and no gravel so selecting suitable soils should not be a problem.
Herbicide residues from the previous crop can limit potato yield and quality. Of most concern are the sulfonyl ureas applied to cereals and imadiazolines used on oilseeds. Follow label directions to minimise the impact of herbicide residues applied to other crops on the potato crop.
Seed sites
Mid West seed potato crops are at higher risk of invasion by aphid virus vectors than summer crops grown in south coastal areas. Select sites that will be upwind of any earlier sown crops. These will be closest to the coast, assuming prevailing winds in winter will be south-westerly to westerly.