Oct 30 (Reuters) - Fertilizer maker CF Industries ( CF )

on Wednesday reported a 68% rise in third-quarter profit, aided

by strong prices for nitrogen fertilizers.

Benchmark ammonia prices reached to about $530 per ton in

September from $410 per ton at the end of June, aided by

production shut-ins in Trinidad and Egypt.

Prices of natural gas, a key feedstock for nitrogen

fertilizers, remained subdued during much of the reported

quarter, helping CF Industries' ( CF ) margins.

The Northbrook, Illinois-based company reported net earnings

of $276 million, or $1.55 per share, for the three months ended

Sept. 30, compared with $164 million, or 85 cents per share,

last year.