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Project Overview

The project determined the cost/benefits of using urea treated with a nitrification inhibitor compared to using standard urea by reducing nitrogen losses through leaching and runoff, and potential production efficiency gains. Research was conducted on two irrigated dairy farms (Atherton Tablelands and Burnett Mary Region) with production systems common in the Great Barrier Reef catchments. Key findings of the research were extended to dairy farmers and service providers through on-site field days and dairy industry publications. Industry current recommended practices and priorities for investment were reviewed and modified as a result of the findings.

This research has contributed to our understanding of nutrient pathways in irrigated tropical and subtropical dairy pastures, and will help to quantify the amounts of nitrogen and phosphorus fertiliser lost through various pathways. The research has also measured the value of the nitrification inhibitor DMPP in reducing losses. However, it is recognised that these findings are highly dependent on seasonal conditions. Differences in some results for the two sites will provide additional insights to the climate, soil and management factors affecting N loss from dairy systems and in reviewing current practices to improve nitrogen uptake efficiency (NUE) in tropical and subtropical dairy farms.

Project Deliverables

The increase in pasture crude protein content associated with application of a nitrogen inhibitor suggests that farmers can apply urea at lower rates to maintain the same level of production by dairy cows.

• Management of N fertiliser application rates according to soil moisture deficits, irrigation availability and predicted precipitation could substantially reduce N losses. This allows for a closer matching of plant N demand to fertiliser supply. In periods of adequate to excess soil moisture, the use of a nitrification inhibitor increases NUE efficiency.
• Before the observed improvements in agronomic NUE lead to higher overall farm NUE, cows grazing pasture with higher crude protein may require rumen fermentable carbohydrate supplements. Feeding such supplements, in combination with increased stocking rates, provides an opportunity for harnessing agronomic gains in NUE and increasing milk production.
• The higher pasture N concentration can be balanced by supplementing cow feed in combination with an increased stocking rate. This approach to harnessing improvements in agronomic NUE leaves the rate of N application unchanged but increases farm production.

PROGRESS UPDATES for this project are summarised here

Study Areas

Field site (Ravenshoe on the Atherton Tablelands) to determine the loss of nitrate through leaching and run-off pathways; on-site field days in 2012 and 2013.

Field site (Gympie in the Burnett Mary region) to determine the loss of nitrate through leaching and run-off pathways; on-site field days in 2012 and 2013.

 Associated Reef Rescue R&D Research

• RRRD020 Mineralisation of N within sugarcane cropping.
• RRRD049 Minimising off-farm movement of N in Nth Qld bananas.
• RRRD039 Integrated assessment of BMP cost-effectiveness and decision tool for regions and landholders.

Related External Research

• Queensland Department of Agriculture, Fisheries and Forestry nitrous oxide research program.
• Dairy Australia, NSW DPI Coastal NSW dairy catchments runoff.
• Dairy Moving Forward – Dairy nitrogen use efficiency and loss.

Publications From This Project

The Research Outcomes Report for RRRD055 is available for download via the Final Report page. The report should be cited as:

Rowlings, D., Koci, J., Nelson, P. and Kowitz, R. (2014). Validating the cost/benefits of improved fertiliser practices and quantifying nutrient loads and pathways from irrigated dairy pastures in the Wet Tropics and the Burnett-­Mary regions. Report to the Reef Rescue Research & Development Program. Reef and Rainforest Research Centre Limited, Cairns (131pp.). ISBN: 978-1-925088-281.

The project results have been summarised at several Reef Rescue R&D forums, visit the Events page.

Project Publications

Anon (2011). Dairy fertiliser efficiency research gets green light. The Northern Dairyfarmer magazine, June-July 2011 edition.

Anon (2012). Nutrient use efficiency research gets under way in Queensland. Reef Rescue News Bulletin – Edition 8 January 2012.

Anon (2012). Nutrient use efficiency research underway. The Northern Dairyfarmer magazine, Feb-Mar 2012 edition.

Anon (2012). Dairying, a way of life for this researcher. and Nutrient use efficiency research gets underway in Queensland. Reef Rescue Water Quality R&D Program Update 4, May 2012.

Anon (2012). New project looks at nutrient loss pathways. The Northern Dairyfarmer magazine, Aug-Sep 2012 edition.

Anon (2013). Field days look at fertiliser efficiency. The Northern Dairyfarmer magazine, Dec 2012 – Jan 2013.

Anon (2012). Fertiliser efficiency research focus at QLD field days. Dairying for Tomorrow Newsletter, Issue 19, December 2012.

Anon (2012). Where is your fertiliser going? Incitec Pivot Agronomy News, September 2012.

Anon (2012). The movement of Nitrogen and Phosphorus fertilisers applied to dairy pastures in the Great Barrier Reef Catchments. Program Handbook and Abstracts, NERP and Reef Rescue R&D.