NEW research hopes to show crop producers the value of soil testing below the first 10 centimetres of their soil to discover what crops live in during dry conditions.
University of Queensland tropical agronomy professor Mike Bell said throughout the years, northern Australian producers had become much better at growing crops and yield production had been going up as crops had access to good nutrients.
He said northern cropping producers were fortunate their clay soils had natural fertility and a reasonable amount of nutrients without having to fertilise.
"When soil profiles are full, you can crop in dry conditions and still get a reasonable crop," he said.
Although some soils wouldn't need any fertiliser compensation in the near future, Dr Bell said producers should be wary of what they were taking out of their soils.
Crop producers should compare taking nutrients from soils to owning a credit card, as what goes out has to go back in for it to continue being effective, Dr Bell said.
"You can only take the credit limit down so far before you have to make some repayments," he said.
Research conducted in conjunction with the NSW Department of Primary Industries, Queensland Department of Agriculture, Fisheries and Forestry (DAFF), and the University of Queensland aims to discover the most effective way producers can fertilise the deeper layers of their soil, which could be losing valuable nutrients.
Dr Bell said the main issue with current soil testing was most producers tested their soils for nutrients within the first zero to 10cm of their soil.
"That's where all the fertilisers and stubble go," he said.
Soil testing deeper would give crop producers a better indication of what their plant roots were living in when their top soil dried out.
"That layer is the critical one," he said.
"The zero to 10cm can give producers a false sense of security."
Because phosphate and potassium are immobile in water, they are unable to naturally redistribute themselves down a paddock's soil profile to replace what has been removed after cropping.
This isn't an issue for nutrients such as nitrogen and sulphur, as they are able to travel, with moisture, further down the soil profile.
Crop roots need to be in shape for a producer to expect a good yield, as an ability to forage down further than a metre deep is important for coping with dry periods.
When producers only fertilise their top soil layer, they could risk their root system missing out on valuable nutrients in dry times.
The challenge to fertilising those deeper layers is to do so in a way the crops can get decent access to the applied fertiliser.
"You have a crop root systems going down to a metre, and in the case of a crop like sorghum, foraging sideways nearly the same distance," Dr Bell said.
"Putting a single fertiliser band into a volume of soil that big makes it difficult for enough roots to be able to 'find' that fertilised spot."
Dr Bell said they wanted to find out how far apart bands should be, how deep producers should place fertiliser products and whether or not different products could be mixed.
The trials are running right across the region from north of Emerald, Queensland, all the way down to the Central West of NSW.
Results so far suggest that if a soil test shows sub soils are low, producers should apply multiple bands of fertiliser that are no more than 50cm apart, and in different spots every year.
"For those immobile nutrients we need to mix it up," he said.
Dr Bell said fertiliser research was necessary because as long as producers continued to crop, nutrients would leave their soils.
"It's an issue that's not going to go away," he said.
"We're going to continue to crop and remove nutrients, so we need to ensure we know what to put where to make the best bang for our buck."
