25 August 1995

Study of nitrogen spreadability to go on year-round

WORK on the "spreadability" of straight nitrogen fertilisers is to be conducted year-round in a bid to pinpoint batch variability.

According to the Fertiliser Manufacturers Association, accurate fertiliser spreading needs a spreader in good working order and fertiliser with good spreading characteristics.

If either is below par the result is uneven placement, inaccurate application rates and, for the farmer, a waste of money.

The FMAs Spread Pattern (SP) rating scheme, operated by Silsoe Research Institute, assesses the flow characteristics, particle size distribution and bulk density of a fertiliser.

This year nine products were tested. Although one scored the lowest rating of SP1, one SP3 and another SP4, manufacturers have asked those not to be identified.

The six products which gained the highest rating of SP5 are:

&#8226 DSM from DSM Mestoffen.

&#8226 Extran from Hydro Agri (UK).

&#8226 Nitram produced at ICI Fertilisers Billingham and Severnside plants.

&#8226 Nitraprill from Kemira Fertilisers.

The rating lasts 12 months – after which another £1000 is spent on a further test.

Current testing is limited to a "window" which excludes activity during the moist winter months. "Fertiliser is hygroscopic," explains SRI project leader Paul Miller. "This means current outside testing – flow rate from a moving tractor, for example – cannot be performed with any accuracy during the winter."

Plans are now afoot to build equipment which can emulate field conditions in the lab.

With spreading discs removed, fertilisers ability to flow evenly "on the move" is assessed at the Silsoe test site at Wrest Park, Bedfordshire.