How does nitrogen move on the paddock and in the environment?

Nitrogen is essential for sugarcane cultivation. It is mostly applied to crops as fertiliser to promote crop health and productivity.

But if the timing, rate, placement, and product selection are not managed effectively, fertiliser is at risk of running off the paddock. Research indicates that dissolved inorganic nitrogen (a key component of fertiliser) discharged from rivers into the Great Barrier Reef has more than doubled over the past 50 years, and in some cases tripled in heavily cropped regions.

Water quality scientists measure farm runoff to highlight key periods of nitrogen losses from paddocks – and this data is communicated back to growers. This includes monitoring high-risk periods, such as the first flush.

Understanding fertilisers and soil health

Nutrient management is critical to promote crop health and productivity. This can include synthetic fertilisers applied to the paddock or additional nutrient inputs, such as mill mud or mulch.

Soil health consists of a balance between chemical, physical and biological components. There are components of the soil that you can change, and there are others that you cannot.

The variability in soil health across landscapes and within paddocks means that certain areas yield better crops than others. Some growers need more nutrient or fertiliser inputs then others, with soil type and condition varying greatly across a district, farm or paddock.

Understanding the conditions of a paddock can inform improved nutrient management while also reducing off paddock losses. Growers can use paddock-scale tools like soil tests, moisture probes, and electro-magnetic mapping to determine optimal nutrient application rates and suitable soil conditioners to enhance overall soil health.

How can fertiliser be managed?

Over the last decade, more growers have been using innovative methods to improve soil health, while reducing standard fertiliser application amounts.

Scientists and extension staff use high-frequency sensors to detect high-risk periods for fertiliser losses. This gives growers accurate data to make informed decisions to minimise runoff losses.

Fertiliser management strategies include:

• Adjusting when and where they apply fertiliser and optimising the timing, placement and selection of products.

  
  

• Effective use of machinery to reduce ground compaction, enhancing water infiltration for better soil health.

  
  

• Using precision technology to apply fertilisers, reducing the use and cost of these products.

  
  

• Introducing rotational cropping, such as legumes, to improve soil health and structure. This reduces the reliance and cost of synthetic fertilisers.

  
  

• By accounting for organic nutrients added to the paddock, such as fallow crops and mill mud, synthetic fertiliser application rates can be lowered. This strategy optimises fertiliser rates, which can increase crop yields and reduce input costs.