The value of Nufarm's step-up hybrid securities has taken a hammering, along with the credit rating assigned to the securities and the share price of the company. Standard & Poor's lowered the rating on the securities issued by Nufarm's New Zealand finance subsidiary, to 'B' from 'BB', a three notch downgrade.The downgrade followed yet another earnings downgrade announced by the company on Thursday. The price of the securities fell from a high of $70 on the day to close at $66. The securities have a face value of A$100.The long term credit rating assigned to Nufarm was lowered by two notches to 'BB' and removed from CreditWatch. A negative outlook was assigned to the rating to reflect the refinancing risk now confronting the company - A$300 million of bank debt must be refinanced within the next six months.Nufarm is currently negotiating with its bankers over a remedy for breaching its interest cover covenant.