Irrigation and fertiliser guidelines for strawberries

Calibrating nutrient solution injection pumps

1. Start irrigation and injection pumps.
2. Adjust each injection pump to the same output.
3. Measure the EC at the dripper and adjust each injection pump up or down to get an EC of about 2.2µS/m in total, for example 1.7µS/m for the fertiliser and 0.5µS/m for the bore water.
4. Measure the output of the injection pump for one minute to work out the flow rate.

Calculation of injection time (worked example)

Assume you are using two 1000L tanks for your fertiliser stock solution.  The following amounts of fertiliser are contained in your two tanks.

75kg calcium nitrate

75kg potassium nitrate

36kg MAP

18kg magnesium sulphate

There is 23.4 kg of nitrogen containing fertiliser in the above recipe. If you have two pumps, each with a flow rate of 120L/hour it will take 2000/120 = 16.6 hours before the tanks empty.

Injection rate – 23.4kg N/16.6 hours = 1.40kg N/hour = 23.5g N per minute

If the area for one station is:

Nine 4-row beds each 125m long x 1.2m wide = 1350m²

and the amount of nitrogen needed is 2kg/ha per day

= 0.2g/m²/day

= 0.2 x 1350m²

= 270g

Injection time = 270/23.5 = 11.5 minutes

To increase or decrease the amount of N, you can either change the injection time or increase the concentration of the recipe provided the final EC does not exceed 2.2µS/m.

Further reading

The external websites listed provide useful information from other growing areas.