GRDC' s nutrient management initiative

by Phil Price, consultant to the GRDC Agronomy, Soils and Environment Program

Many of Australia" s cropping soils are old and leached, and do not naturally contain the level of nutrients needed to sustain high-intensity cropping systems where high rates of nutrient removal occur in grain and fodder. Even in the deep vertosols with higher nutrient levels, years of grain removal are depleting the store of elements needed for good crop growth and yields.

Mass balance calculations (nutrients removed in agricultural products compared with amounts added in fertilisers) suggest that while more nitrogen is often being added than removed, many growers are running down the amounts of crucial elements in their soils such as phosphorus, potassium, sulfur and occasionally magnesium, and trace elements like zinc, copper or manganese. In some cases the soil store of these elements remains adequate to cover the imbalance, but increasing symptoms of deficiency suggest that many growers are losing potential yield due to low nutrient availability.

Growers are well aware of the importance of nutrients, but fertilisers now represent a significant proportion of variable costs and costs are growing faster than the prices obtained for grain. There is increasing pressure to better match these expensive inputs to crop needs and to maximise the returns achieved from nutrient management.

At the same time, fertiliser recommendations developed in the past may no longer be the best for modern farming methods such as full stubble retention and no-till. Past recommendations tended to focus on one element and one crop, whereas growers now look to manage all nutrients across a whole crop rotation sequence. The need for good environmental management, to ensure nutrients are not lost from cropping paddocks causing unwanted impacts off-site, is a further issue for the industry.

These considerations led the GRDC in 2004-05 to establish the nutrient management initiative (NMI). its goal is the adoption of methods by growers to achieve improved nutrient availability and uptake under a range of cropping systems, through:

Within the NMI, nine R&D projects have been funded - they operate across all cropping regions. Eight are working with growers, advisers and fertiliser companies to investigate and improve different aspects of nutrient management; the ninth is focused on how growers use nutrient information and how to deliver new knowledge in ways that enable and promote its adoption.

The mix of outputs from these projects includes:

The NMI projects are described in this supplement. Project teams have identified opportunities for growers to better target nutrients over time (using seasonal forecasts and measured rainfall) and over space (based on farm or paddock production zones).

Results from the NMI will be linked with those from other GRDC initiatives in precision agriculture, soil biology, and subsoil constraints to develop tools that growers can use to maximise the financial return from their nutrient (fertiliser) budget.

For more information: Phil Price, 02 6251 4669,

Region North, South, West