Growing sweet potatoes in Western Australia

Fertiliser

Sweet potatoes require less fertiliser than most other vegetables.

Compost at up to 50 cubic metres per hectare before planting will supply organic matter, nutrients and help retain moisture in the soil.

On sandy soils, apply the following rates of magnesium and trace elements before planting:

The most common trace element deficiencies are boron, manganese and iron. These elements should be applied immediately before planting and, if deficiencies are noticed in the leaves, they may also be sprayed directly on the foliage or applied to the soil after planting.

Use the following program to supply nitrogen, phosphorus and potassium:

Sandy soils

Before planting, apply:

• 200kg/ha double superphosphate

Starting one week after planting until three weeks before harvesting, apply weekly:

• 20kg urea, 25kg/ha muriate of potash

At running, apply once:

• 50kg/ha magnesium sulphate

Loamy soils

Before planting, apply:

• 500kg/ha double superphosphate, 200kg/ha muriate of potash
• 200kg/ha urea

Carnarvon

When plants start to run, apply:

• 50kg/ha urea

Two weeks later, apply:

• 50kg/ha urea

Apply a fertiliser before planting to supply phosphorus. If soil analysis before planting shows high levels of bicarbonate extractable phosphorus, apply less phosphorus. Nitrogen, phosphorus and potassium are easily washed through sandy soils by rain and irrigation. Do not overuse fertiliser, because nutrients leach into lakes and rivers leading to pollution.

Analyse soil and irrigation water before planting, plus one to two analyses of the youngest mature leaves after planting. This lets you adjust your fertiliser program and provides information on nutrients that are deficient or toxic. Some of the suggested nutrients may be deleted or reduced if they are sufficiently high in the irrigation water and soil, including sources from compost and fertilisers from previous cropping.