Publication Date
4-5-2026
Publisher
DPIRD
City
Perth
Abstract
Cultivation of irrigated fodder and forage crops to intensify northern beef production in the west Kimberley and Pilbara has seen significant private investment over the past decade. To support this growing investment, the Department of Primary Industries and Regional Development (DPIRD) carried out replicated, randomised trials on irrigated Rhodes grass near Broome.
High nitrogen (N) inputs are required for subtropical grasses to achieve annual growth rates of up to 40 t DM/ha and there is growing scrutiny of these systems to prevent nutrient losses to groundwater and downstream ecosystems. The research aimed to establish N (urea) response curves to five N rates plus a zero-N control; measure nitrate leaching under these different application rates and create nitrogen-use efficiency (NUE) curves for irrigated Rhodes grass. Plots were harvested monthly to measure biomass yield and crude protein and N-leachate was collected from drainage lysimeters beneath a subset of plots. Yield response plateaued between 2 and 3 kg N/ha/day (or 60–90 kg N/ha after each cut). Protein increased steadily in response to increasing N with crude protein levels of 11.4–12.6% at the yield-plateau point. NUE decreased as N rate increased. At the lowest input rate, 1 kg N/ha/day (or 30 kg N/ha after each cut), 65% of applied N was recovered in harvested product. When 3 kg N/ha/day was applied, just 51% was recovered in the harvested product. Rates above 3 kg N/ha/day resulting in nitrate leaching from wet season rainfall. The data is being used to inform fertiliser decisions in irrigated Rhodes grass systems and support proponents seeking the necessary environmental approvals to sustainably develop fodder irrigation systems on pastoral leases.
Number of Pages
8
Keywords
irrigated fodder, crops, forage crops, beef, livestock, Kimberley, Pilbara, Broome, Western Australia, nitrogen, Rhodes grass
Disciplines
Agronomy and Crop Sciences | Beef Science
Recommended Citation
Milazzo, C,
Ham, C,
and
Moore, G.
(2026), Nitrogen-use efficiency of irrigated Rhodes grass in Northern WA. DPIRD, Perth. Report.
https://library.dpird.wa.gov.au/fc_researchrpts/53
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