Reduced pass harvesting of cauliflower and broccoli

A key to uniform crop maturity is even plant growth from transplanting through to harvest. Crop maturation uniformity can be improved by  changes to fertiliser and irrigation management but it is also influenced by factors which cannot be easily controlled such as plant genetics and environmental conditions. Due to these other factors it is not possible to get all of a crop maturing at the same time. Trials have shown that about 80% of a crop can be uniformly mature for one harvest if fertiliser and irrigation are carefully managed.

The following management system is particularly suited to crops grown in summer months on soils that have some clay content and adequate water-holding capacity. The irrigation techniques are not suitable for sandy soils due to their low water-holding capacity which necessitates more frequent watering.

These crop management techniques were developed and tested on karri loam soils in the Manjimup region, about 300km south-west of Perth. Due to the high degree of variability of soils across vegetable growing regions and the impact of soil type on crop development, the reduced pass harvest system should be tested on-farm before implementing on a large scale.

Fertiliser

The strategies for fertiliser management to improve crop uniformity include changes to application methods, timings and rates:

• Apply basal fertiliser in an incorporated strip, rather than banded beneath the plant. Incorporation leads to a slight increase in yield, reduced growing time and fewer harvests.
• Apply nitrogen-based fertiliser regularly and in small amounts throughout the life of the crop. Applying large amounts occasionally may lead to fluctuations in growth rates and uneven growth across a crop. The first application of nitrogen fertiliser after transplanting should be within one week and thereafter applied ‘little and often’.  See table 1 for an example fertiliser application schedule used for reduced pass harvest demonstration crops.
• Apply post-transplant fertiliser in a liquid form. If possible, dissolve granular fertiliser and apply through a boom spray rather than in a granular form through a spreader. This method is more accurate as each plant receives a similar amount of fertiliser. It can also save money as fertiliser application is more targeted and not wasted on non-cropped areas. Ensure irrigation is going when nitrogen-based liquid fertilisers are applied to prevent damage to plants.

The last three applications of calcium nitrate may not be required, depending on harvest date.