Soils and fertiliser
Well-drained loams, peaty sands or gravelly loams are preferred, but good crops can be produced on sandy soils providing they are fertilised well. A neutral to slightly alkaline soil is optimum; apply lime if the pHCa is less than 6.0.
Before planting on loamy or gravelly loam soils, apply 1500kg/ha of a compound NPK fertiliser with an analysis around 8% nitrogen, 12.5% phosphorus, 11% potassium and trace elements in strips 20cm wide and incorporated to 15cm in the planting lines.
One week after planting, apply 50kg/ha of urea by broadcasting or spraying — with immediate sprinkler wash off to avoid foliage damage — plus 20kg/ha of a soluble boron containing product such as borax. Thereafter, at two-weekly intervals, apply 150kg/ha urea.
About four weeks before the first harvest, switch to calcium nitrate at 150kg/ha at 14 day intervals and continue until harvesting ceases. After heavy and prolonged rain, apply more fertiliser. At monthly intervals, include dressings of 50kg/ha of magnesium sulphate with the above.
Before planting on sandy soils, broadcast and incorporate 30 cubic metres of compost per hectare. On the day of planting, broadcast a mixed granular NPK product with an analysis of around 12% nitrogen, 5% phosphorus and 14% potassium plus trace elements directly over transplanted seedlings. Thereafter, broadcast this NPK product at 100kg/ha at three to four day intervals until 17 days after planting. About 21 days after planting, increase the rate to 400kg/ha and apply it by banding about 15cm either side of the rows at weekly intervals for the next 7 to 8 weeks.
Thereafter and during the harvest period, apply calcium nitrate by fertigation at 150kg/ha weekly.
At monthly intervals, include dressings of 50kg/ha of magnesium sulphate and apply a soluble boron product soon after planting and again at around 10 weeks after planting at 10kg/ha each time by spraying (with immediate wash off) or fertigation.
Trace elements may be required at 12 to 18 month intervals in the vegetable program. A suitable mixture would include manganese sulphate (25kg/ha), copper sulphate, ferrous sulphate, zinc sulphate and borax (each applied at 18kg/ha) and sodium molybdate (2kg/ha).
Preventive sprays of some trace elements may be needed at the following rates in the seedling stage:
- Molybdenum: sodium molybdate at 1g/L, especially where soils are acidic. Spray seedlings in trays before planting.
- Manganese: manganese sulphate at 8g/L, especially on alkaline soils if symptoms appear. Spray in the field within four weeks of planting out.
Soil analysis before planting and leaf analysis after planting, plus nutrient analysis of the water, will help you adjust your fertiliser program.
Irrigation
Comprehensive information on the principles of irrigating vegetable crops in WA can be found on the vegetablesWA website. Irrigation rates for your specific location and circumstances can be calculated using the irrigation calculator.
To minimise salt damage and associated yield loss, irrigation water should have total soluble salts content of less than 220mS/m or about 1200mg/L.