Feb 22 (Reuters) - The Baltic Exchange's main sea freight index, which tracks rates to ship dry commodities, fell for a sixth straight day on Wednesday on sharply lower panamax rates.
The overall index, a gauge of the cost of shipping commodities such as iron ore, cement, grain, coal and fertiliser, fell 2 points or 0.28 percent to 704 points.
"There is definitely a weak downturn, particularly in the Atlantic, for the panamaxes," said Peter Norfolk, research director at freight broker FIS.
The Baltic's panamax index dropped 3.22 percent, with average daily earnings for panamaxes falling to $6,971.
Earnings for panamaxes, which usually transport 60,000 to 70,000 tonne cargoes of coal or grains, have dropped 47 percent this year.
"The panamax market in the Atlantic is really in need of the boost from the grain export volumes out of South America, which really have not been visible so far this year," Norfolk said.
Prospects for grain crops in major exporters Brazil and Argentina have suffered from weeks of dry weather.
The Baltic's capesize index rose 0.55 percent on more positive freight rates for iron ore from Brazil and South Africa.
Iron ore shipments account for around a third of seaborne volumes on the larger capesizes, and brokers said price developments remained a key factor for dry freight.
Average daily earnings moved slightly higher for capesizes, which typically transport 150,000 tonne cargoes such as iron ore and coal, to $5,278. However, earnings are still down 81 percent this year.
The main index, which factors in the average daily earnings of capesize, panamax, supramax and handysize dry bulk transport vessels, is down 59 percent this year. (Reporting by Ratul Ray Chaudhuri in Bangalore, additional reporting by NR Sethuraman in Bangalore, editing by Jane Baird)