Preface: nutrient management by the Australian grains industry.(Report)

The contributions to this special. edition of the Australian Journal of Soil Research report recent research undertaken as part of a Nutrient Management Initiative established by the Grains Research and Development Corporation (GRDC). The Corporation is a statutory authority established to plan and invest in R&D for the Australian grains industry. Its primary objective is to support effective competition by Australian grain growers in global. grain markets, through enhanced profitability and sustainability. The Nutrient Management Initiative operated as a national. R&D program over the period 2004 to 2008, with projects in each of the three major grains regions (west, south, and north).

Many of Australia's cropping soils are old and leached, and do not naturally contain the level of nutrients needed to now sustain high-intensity cropping systems with high rates of nutrient removal in grain and fodder. Even in soils with higher natural. nutrient levels, many years of grain removal. is depleting the store of elements needed for good crop growth and optimal. yields. Mass balance calculations (nutrients removed in agricultural. products compared with amounts added in fertilisers) suggest that while more nitrogen (N) is often being added than removed in modern cropping systems, many growers are running down the amounts of crucial. elements in their soils such as phosphorus (P), potassium (K), or sulfur (S), and occasionally magnesium (Mg) and trace elements such as 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. crop yield due to low nutrient availability.

Grain growers are well aware of the importance of nutrients in soil fertility, but fertilisers now also represent a significant proportion of all variable costs and their costs have been growing faster than the prices obtained for grain. Increasing prices reflect both the limited world supply of fertiliser ingredients, including N, P, and K and the gradual. move to lower quality sources, as well as structural. constraints which mean the fertiliser industry cannot respond immediately to the increased demand being driven primarily by developing countries. Biofuel production is adding to fertiliser demand, while there is increasing competition for some of the raw ingredients of fertiliser manufacture, for example natural. gas that can be used directly as an energy source or as a feedstock for N fertiliser manufacture. Hence, there is increasing pressure to better match these expensive inputs to crop needs and to maximise the returns achieved by grain growers from their nutrient management.

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

These considerations led the GRDC, in 2004-05, to establish a national. Nutrient Management Initiative (NMI), whose goal. was the adoption by grain growers of methods to achieve improved nutrient availability and uptake under a range of cropping systems.

Within the NMI, 9 R&D projects were funded. Eight worked with growers, advisers, and fertiliser companies to investigate and improve different aspects of nutrient management; the ninth focused on how growers use nutrient information and on delivery to the industry of the new information from the NMI in ways that enable and promote its adoption. The mix of outputs from these projects included:

* mass balances for key nutrients at paddock, property, and catchment scales to identify potential. imbalances and off-site losses.