Most commodity prices rallied Friday as encouraging news about the U.S. job market raised hopes that demand may improve.

Prices rose across the board, from oil and gold to wheat. The turnaround came after two days of declines as central banks in the U.S. and Europe failed to take immediate action to help economic growth.

The Labor Department said 163,000 jobs were added in July after three months of weak hiring. More jobs may help strengthen demand for commodities, from gasoline to metals in manufactured products and agriculture crops used in food and apparel. That's because employed Americans may spend more and consumer spending accounts for about 70 percent of economic activity.

Commodities also benefited from a weaker dollar. Commodities are priced in dollars so a weaker dollar makes them cheaper for traders who use other currencies.

Benchmark oil soared $4.27, or 4.9 percent, to finish at $91.40 per barrel, heating oil gained 8.38 cents to $2.9261 per gallon and wholesale gasoline ended up 6.14 cents at $2.931 per gallon. Natural gas dropped 4.3 cents to $2.877 per 1,000 cubic feet.

Gold for December delivery rose $18.60 to finish at $1,609.30 an ounce and September silver jumped 80.6 cents, or 3 percent, to $27.801 per ounce. September copper gained 7.7 cents to $3.3675 per ounce, October platinum rose $26.60 to $1,414.40 per ounce and September palladium increased $10.35 to $578.20 per ounce.

Meanwhile, concerns about the nation's damaged corn crop mounted as heat continued to dominate the Midwest with no substantial rain in the forecast.

The U.S. Agriculture Department will update crop conditions in a report on Monday. Later next week, it will release a new forecast of supply and demand for corn, soybeans, wheat and other crops.

Some analysts are expecting corn yields to fall below 130 bushels per acre or even down to 120 bushels per acre, which would be the lowest since 1996, said Sterling J. Smith, a commodity strategist at Citi Institutional Group. The USDA last month predicted the harvest would equal a yield of 146 bushels per acre.

The soybean crop will be past the time that it could be helped by rainfall within a matter of days, Smith said.

Both corn and soybeans are in short supply globally now and hopes are fading that the U.S. harvest will do much to help inventories.

Meanwhile, wheat prices jumped on speculation that adverse weather is damaging crops in Russia, Smith said.

Corn for December delivery rose 11.75 cents to end at $8.075 per bushel, November soybeans increased 12.25 cents to $16.2875 per bushel and September wheat gained 26.25 cents, or 3 percent, to $8.9125 per bushel.