The ''ASX aware'' letter is the company's third in less than a year, with the others also coming after shock profit downgrades.

At the same time, Nufarm is blaming an ''oversight'' for its failure to disclose a breach of a key banking covenant in its initial announcement this week.

In response, Nufarm maintained it was first aware it would miss its annual earnings guidance on Tuesday evening.

It also said that its previous guidance was ''expressed to assume average climatic conditions''.

The farm chemicals group did not mention it would breach its interest cover ratio covenant in its initial ASX announcement on Wednesday, issuing a ''clarification'' the next morning.

Nufarm's head of corporate affairs, Robert Reis, said the company realised the ''oversight'' just before a media and analyst conference call on Wednesday, but did not explain why managing director Doug Rathbone only revealed the breach after fielding a media question on the subject.

''You can make a judgment on that, but the fact is that a question was asked and answered, and irrespective of … any comment that would have been made on that conference call, the further statement would have been issued,'' Mr Reis said.

''The fact that the interest cover breach was not specifically mentioned in the statement [on Wednesday], is an oversight on our part.

''That oversight was subsequently recognised and the further clarification statement was issued prior to the market opening [on Thursday] so that the market was fully informed.''

In an email sent to all Nufarm staff that was obtained by The Age, Mr Rathbone admitted that he was ''personally very disappointed'' with the company's performance and issued a rallying cry to his staff, urging them ''not to be distracted'' by the negative publicity.

''The timing and extent of the adjustment to our forecast earnings inevitably raises questions about the transparency of the business; about the financial strength of the company; and about the competence of management,'' Mr Rathbone wrote.

Nufarm slashed its earnings guidance in half on Wednesday - its fifth profit downgrade in little more than a year - after its final quarter result was devastated by poor weather conditions and price pressures.