Efficient Sand Integration

Crop

Irrigation - Broccoli

Irrigating Brassica vegetables on sand

Following the principles of good irrigation practice Brassica crops (eg broccoli, cauliflower and cabbage) growing on sand can be irrigated to the following schedule.

Water requirement (mm) = Evaporation (mm) x Crop factor

Crop factors for transplanted Brassicas

Week

1 - 2

3 - 4

5 - 6

7 - 8

8 until harvest

Crop Factor

1.0

1.1

1.2

1.4

1.5

Brassicas must grow evenly with no moisture stress. Critical periods are immediately after transplanting, then curd initiation (6 – 8 weeks) and head forming.

After transplanting a watering of 4mm is sufficient to “bed” the plants. Apply at least four light waterings of more than 1 mm each day for the first week to achieve a crop factor of at least 1.0.

Once established deep rooting should be encouraged by once daily watering until the daily requirement exceeds 8mm. If 2 waterings are required, apply a minimum of 6 mm early to mid morning and the remainder between 1 and 3 pm. During the cooler months watering of plants grown for more than 4 weeks can be delayed until a deficit of 8 mm of evaporation (daily evaporation minus rain) has been reached.

Split applications may be needed to cool a crop or control wind blown sand but at least one application should be sufficient to penetrate the soil to a depth which encourages deeper rooting.

The above table relates to crops grown on Karrakatta sand low in organic matter at the Medina Research station and represents a guide for achieving optimum yield on this soil type.

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