Introduction
The 3Phase fertiliser program was developed by DAFWA in response to the need to phase out poultry manure because of community concerns with its use in near-metropolitan areas. Although a useful soil amendment and source of nutrients, poultry manure stockpiles on vegetable farms provided a breeding ground for stable flies and created odour problems.
This 3Phase fertiliser schedule is based on four years of trials with broccoli grown on the sandy soils of the Swan Coastal Plain in Western Australia. It gave the highest yields and best quality throughout the year, while being practical to apply with mechanised equipment, saving labour and minimising fertiliser losses to the environment.
These sandy soils are a free-draining, easily worked growing medium for a variety of vegetable crops. Nutrients are freely available in the soil solution for uptake by plants. Some nutrients are highly mobile and easily lost through leaching.
Nitrogen in the form of nitrate is particularly susceptible to leaching and is a major groundwater pollution concern.
A good commercial fertiliser program should:
- maximise yield and quality with minimum fertiliser input and cost
- minimise adverse off-site effects, including loss through leaching, wind drift or overspray.
The schedule is based on research conducted on some of the least fertile sandy soils in Australia to develop cost-effective strategies for producing high yield in a ‘worst case’ situation.
Trial sites had no prior vegetable cropping history and irrigation water did not contain nutrients. We did not use soil amendments such as compost and manure (except as current commercial ‘controls’), but trials were grown in rotation with lettuce and celery crops. There was some carryover of nutrients from crop residues after each crop, as there is in commercial vegetable production.
Fertiliser and cost savings are achieved in the 3Phase method by making informed choices about fertiliser type, application rates, methods and timing — matching fertiliser application to crop demand.
To achieve this, the life of the crop is considered in three phases: establishment, rapid growth and maturation (Figure 1).
Different fertiliser strategies are used to optimise growth in each of these phases and meet the criteria of a ‘good program’.