NEW YORK—Rice futures sank to a six-week low Friday, falling for a fifth day on hopes that exports from Pakistan and Japan will ease fears of a shortage of the staple consumed by half the world’s population.

Other commodities traded mostly higher, with crude oil surging to a trading record near $128 a barrel and gold briefly jumping back above $900 an ounce.

Pakistan, the world’s fifth-largest rice exporter, said Thursday it will allow overseas shipments of 1 million tons of rice, lifting a two-week export freeze imposed to slow spiraling domestic prices. Meanwhile, Jap...