Deep Soil Nitrogen & Sulphur Testing

Levels of soil Nitrogen remaining after the 2016 season will vary significantly, depending on the yield and protein of harvested crops, paddock history, rainfall, plus soil Organic Carbon levels. Nitrogen loss factors such as denitrification, leaching and volatilisation, have also had a strong influence on Nitrogen remaining.

Recent rainfall would have stimulated significant mineralisation. Rates of up to 1.0 kg Nitrogen /ha /day are likely, depending on soil moisture and temperature, plus levels of soil Organic Carbon.

Sulphur levels may also vary after such a wet year, as Sulphur moves in the soil at approximately half the rate of Nitrogen. It is likely that Sulphur levels in the subsoil may be adequate, but in some soils the Sulphur may have been leached below the expected root zone.  Given the potential variability in soil Nitrogen and Sulphur levels, deep soil tests will be an important tool for Nitrogen and Sulphur decision making in 2017. Tests should be done in April or early May, so that results can be used in calculating application rates, allowing products and spreading to be organised well in advance of when applications need to be made.

Most effective results will be achieved by:

• Testing a representative number of paddocks

• Testing paddocks which are expected to be both high and low in Nitrogen status

• Testing to 60cm depth

• Segmenting tests down the soil profile: 0-30cm, 30-60cm

• Taking soil samples early so that results are received in a timely manner before topdressing decisions are made