12 April 2002

Stick to best practice for optimum N

DONT be swayed by shifting fertiliser or grain prices into making unjustified changes to nitrogen inputs to winter wheat and oilseed rape.

The advice, from FACTS consultant Ian Richards, is based on 15 trials of each crop from 1994-1998. "The results show that the optimum N rate alters little for quite large variations in both crop and fertiliser price."

For example with wheat at £60/t and ammonium nitrate at £120/t, the average optimum N input is 195kg/ha. But even with grain at £100/t and fertiliser costing £80/t, the optimum N is only 25kg/ha higher.

"So drastic reactions to the current economic position could cause much bigger losses than any savings realised," warns Dr Richards.

He also echoes the Fertiliser Manufacturers Association concern that some farmers are confused about the implications of NVZ regulations, which could extend to a much larger part of the UK later this year. Some even mistakenly believe the proposed regime would not allow them to use any fertiliser, according to the FMAs Jane Salter.

Key requirements for N fertiliser use in NVZs affect timings not amounts. Provided growers can show applications meet crop requirements there are no specific limits on quantities, notes Dr Richards. &#42

&#8226 Stays relatively constant.

&#8226 Proof from five years trials.

&#8226 Grain and fertiliser price little impact.

&#8226 Crop need key in NVZs.