While pulses are renowned for supplying up to $2 billion worth of soil nitrogen to bulk up subsequent cereal yields and lift grain protein levels across Australia, their own nutritional needs have often been overlooked.

Zed Rengel of the University of Western Australia has therefore examined pulses to see what effect various fertilisers have on dry matter production.

To determine the nutrient response of pulses required hundreds of data sets. Collaborating with the Western Australia Department of Agriculture, CSBP and the Centre for Legumes in Mediterranean Agriculture, Professor Rengel generated that data by calibrating pulse nutrient responses against wheat and extrapolating results across hundreds of past wheat trials.

Supported by growers and the Federal Government via the Grains Research and Development Corporation (GRDC), this information then anchored a pulse fertiliser recommendation system.

With pulses grown mainly on fine-textured alkaline soils, which are rich in potassium and sulfur, the investigation was limited to phosphorus (P) and zinc (Zn) response.

Field pea, faba bean and chickpea were compared to wheat after being planted in P-fertilised field plots. Wheat initially accumulated dry matter slower than the pulses, but surpassed them after four weeks. However, where P was not added, the pulse crops maintained their production edge, proving they were not as dependent on P-fertiliser for optimal growth.

Pulses have special roots which can extract P from the insoluble compounds it forms with other elements in the soil. This was evident in their limited response to the extra quantities of plant usable P applied as fertiliser.

Among the pulses tested, chickpea was the least responsive to P applications, suggesting it had the greatest capacity to naturally extract it from the soil. Chickpea was also the most adept at accessing soil Zn.

Understanding the dynamics of pulse responses to fertilisers allowed the GRDC project to generate a response curve prediction model to determine how much P to apply. According to Professor Rengel, growers will generally find they need less fertilisers than they thought. The model is available from Dr Bill Bowden, Department of Agriculture, Tel 08 9690 2190.