Call for rethink on cotton N performance indicators

Susan Webster, July 12, 2023

CURRENT cotton industry nitrogen performance indicators do not represent irrigated production in
southern Queensland and southern New South Wales, according to researchers.

Scientists from AgriFutures Australia and the University of Queensland reported that industry
benchmarks of partial factor productivity for N and internal N use efficiency were not suitable.

They reported that crops grown with soil N alone only accumulated crop N and lint yield at 75 percent, and 79pc of crops produced 95pc of site-maximum lint yield.

And, at fertiliser rates standardised to produce 95pc of site-maximum lint yield, nitrogen budgeting
indicated only 25-30pc of the potentially available soil and fertiliser nitrogen was present in crop
biomass and soil nitrogen at the end of season.

AgriFutures Australia’s general manager research John Smith said variations of soils and background soil-nitrogen levels in the two outlier regions presented challenges to standard fertiliser rates.

“Current cotton industry nitrogen performance indicators have been developed in a narrow geographic region and do not represent production in these other areas,” he said.

“Improving fertiliser nitrogen efficiency in irrigated cotton will require an understanding of site-
specific factors that influence nitrogen availability, crop nitrogen demand and the ability of the crop
to produce lint from nitrogen accumulated in biomass.

“Further research is required to develop the understanding of regional factors that influence crop
nitrogen performance for the industry to improve its nitrogen use efficiency.”

The researchers aimed to benchmark soil and fertiliser nitrogen use efficiency in irrigated cotton
crops in the two outlier production areas, and to determine whether the current industry
benchmarks were relevant in those regions.

They conducted eight field experiments were conducted over three growing seasons on commercial
farms in southern Queensland and southern NSW, applying differing rates of urea to fields using
surface or overhead irrigation.

Other researchers involved in the study were UQ professors Shu Fukai and Michael Bell.


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