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Root systems that respond to banded fertilisers

Crop varieties that can exploit fertiliser placed in bands could be crucial to future cropping yields and fertiliser use efficiency. Many of our cropping systems are slowly running down the native soil fertility. Ongoing cropping in these soils could depend more and more on nutrients placed into the soil as fertiliser. When we place fertiliser deeper into the soil it gets distributed in bands.

When fertilisers are banded it presents a different scenario – from the point of view of the plant – to having nutrients spread more evenly through the soil. Varieties that are better able to exploit concentrated patches of nutrients might be more successful with banded fertilisers.

Chris Guppy at the University of New England is looking for differences in the ability among some of our current crop species and varieties to exploit nutrient-rich patches within the soil. So far he’s looked at 10 wheat varieties, 5 barley varieties and 5 chickpea varieties, and their responses to patches of enriched nitrogen, phosphorus, potassium and sulfur.

Using CAT scan type imagery to define the root system, much more variability than was expected was seen in how effectively root systems were able to proliferate in phosphorus bands.

There wasn’t much response to patches enriched with sulfur and potassium. This is not that surprising because these are more mobile nutrients than phosphorus in the soil. It might not be in the plant’s best interests to invest energy in developing its root system into a patch of nutrient that may not be there in a few weeks.

Surprisingly very little root proliferation in response to patches of nitrogen was seen. This is unexpected as other research had indicated a response to concentrated nitrogen was likely. Researchers are going to continue investigating.

Very little root proliferation responses were seen in the chickpeas until about 40 days old. It may be that legumes are going to have very limited capacity to make use of banded phosphorus. This means that phosphorus will need to be placed very close to legume seed or seed rows being located directly over deep bands,  or it will not be of use to the plant.

Acknowledgements

Chris Guppy, UNE

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