The majority of Queensland lettuce is produced in:
- The Lockyer Valley ( Autumn, Winter, Spring)
- Eastern Darling Downs (Spring, Summer, Autumn)
- Granite Belt (Spring, Summer, Autumn)
Soil requirements for growing lettuce
Lettuce thrives in loose, nutrient rich soils with a pH between 6.0-6.8.
The nitrogen requirements of of lettuce depend on the variety, soil type and season. Excess nitrogen levels are a concern for three reasons:
- some varieties may not heart up properly with high nitrogen applications
- the excess nitrogen may endanger groundwater quality, since it can be leached through the soil
- excess nitrogen application is associated with reduced shelf life as well as with the physiological disorder “Jelly Butt”, which reduces yield and market acceptance.
Plan your irrigation carefully according to lettuce variety and production season. Lettuce has shallow root system and is highly sensitive to water stress and tipburn.
- During cool-season production, water every 4-6 days once the crop is established.
- In warm conditions, you may need to irrigate daily even on clay soils.
You may need to irrigate frequently:
- if you’re using overhead sprinkler systems on sandy soils (irrigate daily)
- if you’re using drip systems
- If you’re establishing transplants (daily)
- In hot conditions
A tensiometer measures soil moisture. It is an instrument designed to measure the tension or suction that a plants' roots must exert to extract water from the soil. This tension is a direct measure of the availability of water to a plant. Use tensiometers to help you determine irrigation requirements once the crop is established.
- Place the tip of the shallow tensiometer about 15 cm below ground level and another one about 45 cm deep. The shallow tensiometer tells you when to irrigate:
- In cool conditions, irrigate when the gauge is near 25 centibars (kPa).
- In warm conditions irrigate when the shallow tensiometer reads 15 or 20 kPa.
- The deep tensiometer should normally read between 10 and 15 kPa.
- If it drops to less than 5 kPa after irrigation, you should apply less water next time and monitor what is happening using the deep tensiometer.
It is best to have a tensiometer site for each planting. Tensiometers are useful for scheduling irrigations once the crop is established, ten days to two weeks after transplanting.
A hydroponic solution should be: easy to make and, if possible, use fertiliser-grade nutrients.
Nutrient solution recipes are published by researchers and hydroponic societies, and these could be used as the basis of a good hydroponic solution. Published nutrient solutions often have slightly different recipes for summer and winter production so you can change them with the season.
If you’re buying a nutrient solution from a store, check that it has a detailed nutrient analysis. If you have growing problems, being aware of the nutrient make-up will help you to find the correct solution.