Crop response to deep placement of phosphorus in a Vertosol soil in the Northern Grains Region of NSW.

Thomas Tendo Mukasa Mugerwa1*, Ricky Graham1 and Peter Formann1.

1 New South Wales Department of Primary Industries, Tamworth NSW 2340

(*Corresponding author –


The fertile soils of the Northern Grains Region supported cropping for many years before yields started to become limited due to nutrient availability. Phosphorus (P) is a key plant nutrient which has traditionally been applied as starter fertiliser, with the seed. However, due to the relative immobility of P, P rundown in subsoil (10-30 cm) readily occurs in soils in the Northern Grains Region. This is beneath both where starter fertiliser is placed and where plant matter is returned. Low levels of phosphorus in the subsoil can have significant impacts on crop yield, particularly during periods where the topsoil (0-10 cm) is dry. The aim of this experiment was to investigate whether or not placing P at depth would increase grain yields of crops growing in a Vertosol under limited rainfall. An experimental site with varying rates of deep-placed P was established at Gurley, New South Wales (NSW), in 2015. In 2017, a wheat crop was sown within these varying P treatments in the presence or absence of starter fertiliser.   Where starter fertiliser was applied, a significant yield response was recorded where deep-placed P was applied at a rate of 80 kg P/ha.  Results of this study demonstrated the potential impact on wheat yields of placing P deeper in the profile.Ultimately, the 4 rights (4Rs) of nutrient stewardship should be closely followed in order to increase the chances of getting a favourable return on nutrient application.


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography Graham Centre for Agricultural Innovation, Charles Sturt University

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