Fertilisers and irrigation
Apply the following rates of magnesium and trace elements to the soil before planting:
50kg/ha magnesium sulphate to supply magnesium
20kg/ha manganese sulphate to supply manganese
18kg/ha borax to supply boron
18kg/ha iron sulphate to supply iron
18kg/ha copper sulphate to supply copper
18kg/ha zinc sulphate to supply zinc
2kg/ha sodium molybdate to supply molybdenum.
Before planting, apply compost at up to 50 cubic metres per hectare. This adds organic matter, supplies nutrients for the first weeks, and helps retain moisture.
Apply double superphosphate at 0.6t/ha before planting. This may be reduced if a soil test shows that phosphorus levels are more than 80mg/kg or if compost is used. Double superphosphate is preferred to single superphosphate as it contains less cadmium.
After planting, apply weekly topdressings of nitrogen (25kg/ha urea) and potassium (25kg/ha muriate of potash) in the irrigation water. Reduce nitrogen if the irrigation water contains more than 10mg/kg of nitrate nitrogen. Apply 50kg/ha magnesium sulphate four weeks after planting by the same method.
Apply foliar sprays of zinc sulphate at 4g/L and iron chelate at 2g/L as required if plants show symptoms of deficiency.
The suggested fertiliser program is for a low fertility soil. Analyse soil and irrigation water for nutrients before planting, plus one to two analyses of the youngest mature leaves after planting. This will let you adjust your fertiliser program and will provide information on nutrients that are deficient or toxic.
Do not apply excess fertilisers because nitrogen, phosphorus and potassium are easily washed through sandy soils by rainfall and irrigation.
Sprinkler irrigation is preferred on sandy soils, but drip irrigation could be used on heavier soils.
Irrigation water should contain less than 1000mg/L of total soluble salts.
Comprehensive information on the principles of irrigating vegetable crops in Western Australia can be found at www.vegetableswa.com.au. Irrigation rates for your specific location and circumstances can be calculated at irrigation calculator.