Variety
Varieties vary markedly in their response to changes in plant density. Large leaf and frame varieties need more space and may not be able to reach their full yield potential at higher densities due to increased inter-plant competition, especially some cauliflower varieties.
Rotation
If cauliflower and broccoli are grown in rotation with other vegetables such as lettuce, then three and four-row planting configurations can be an advantage. The same machinery can be used for multiple crops giving greater return on capital investment.
Market requirements
Altering planting density can control the size of cauliflower curds and broccoli heads. In trials the average curd or head weights at all recommended densities met size requirements for export and domestic markets, although higher density plantings tended to produce more smaller curds or heads.
Consumer preference towards smaller cauliflower curds and broccoli heads has increased in recent years due to reduced family size and moves towards convenience foods. Production systems which use higher planting densities to produce more smaller heads or curds are likely to suit this trend towards smaller product size.
Management changes
Fertiliser and irrigation regimes may need to change if planting densities are changed. With increased density more water and nutrients are needed to maintain good plant growth. When planting more densely, soil moisture levels and plant condition should be monitored carefully to ensure plants do not become stressed.
Pest and disease pressure could increase in the competitive environment within high density plantings and crops will need to be monitored closely. This is particularly true for crops grown in winter where wet conditions and reduced air flow in high density plantings may lead to a higher incidence of fungal diseases.
Consistent monitoring for pests and diseases should be part of standard crop management. Pest control may be also more difficult in higher density plantings with closer spacing making it more difficult to achieve good spray coverage.
Crops planted at higher densities can be more difficult to move through for operations such as insect monitoring, manual covering of cauliflower curds and manual harvesting. Closer spacing can also impact on ease of cultivation. These factors need to be considered before you alter your crop row configuration and/or density.
Acknowledgement
Horticulture Innovation Australia, utilising the National Vegetable Levy, funded this work through project VG04008.