Nitrate Paradigm Does Not Hold Up for Sugarcane

What is the problem?

Nitrogen in the form of nitrates is commonly thought of as the most available form of nitrogen for plants. Sugarcane fields commonly report low N efficiency with high nitrogen losses from nitrate leaching, ammonia volatilisation, and gaseous emissions through microbial conversion of ammonium and nitrate. As sugarcane is considered the most suitable crop for biofuel production, inefficient N use needs to be addressed for the industry to be sustainable.

What did the research involve?

• Plant and soil analyses for nitrogen levels and forms at various stages of growth.
• Statistical analysis of available global data on nitrogen fertiliser use in sugarcane vs levels of production to establish N efficiency values for various countries.

What were the key findings?

Increased nitrogen use does not translate to increased production levels:

• Brazil currently accounts for 42% of global sugarcane production but only 25% of N-fertiliser use.
• 2nd and 3rd ranked producer countries India and China produce 31% of global sugarcane but apply 50% of N-fertiliser.

Their results suggest that sugarcane:

• prefers nitrogen in the form of ammonium
• has a low capacity to use/store nitrate during periods of high N availability (for instance, during the first 3 months of crop production when fertiliser rates are highest)
• and that this contributes to the pronounced accumulation of nitrate in sugarcane Soil Management and subsequent N losses (through effects such as nitrate leeching)

Final comment

This research shows a major flaw in current sugarcane production methods, explaining how current nitrogen fertiliser regimes are ineffective and costly to both profits and environment. They further suggest it might be possible to breed cultivars that have a greater nitrate uptake ability.

This paper was summarised by Mia Courtney (Agricultural Sciences Student – La Trobe University)  and reviewed by Nickala Best  (PhD Student – La Trobe University).  Learn more about Mia and Nickala  here.