NEW DELHI, Aug 11 (Reuters) - Ample monsoon rains have accelerated the planting of summer-sown rice in India, according to the latest farm ministry data, after a slow start to the sowing season that began in June.

Crop-nourishing monsoon rains picked up in July and August, allowing farmers to plant 32.8 million hectares (81 million acres) with rice by Friday, up 5.1% from the same period last year.

An increase in rice planting in India, the world's second-biggest producer of the grain, will ease concerns that supplies could be squeezed after New Delhi, in a surprise move late last month, ordered a halt to its largest rice export category.

India's decision to ban overseas shipments of non-basmati white rice pushed prices to multi-year highs, as trade and industry officials believe shipments by the world's largest exporter of the grain could be halved.

Farmers typically start planting rice, corn, cotton, soybeans, sugarcane, peanuts and other crops from June 1, when crucial summer monsoon rains are expected to begin drenching the country where nearly half the farmland lacks irrigation.

India's monsoon rains were 5% above average over June and July as a whole, but had fallen 10% below normal in June before rebounding to 13% above average the following month.

The weather office defines average, or normal, rainfall as between 96% and 104% of a 50-year average of 87 cm (35 inches) for the four-month season.

The delayed arrival and lower rainfall in June, especially in some southern, eastern and central states, held back summer crop planting, even though the monsoon advanced to cover the entire country almost a week earlier than normal.

In some regions, including breadbasket states such as Punjab and Haryana, torrential rains in July triggered floods but dry weather prevailed in other parts of the country.

Farmers had planted 18.3 million hectares with oilseeds, including soybeans, by Friday, a marginally smaller area than a year earlier.

Corn was planted on 7.9 million hectares, up from 7.7 million hectares a year earlier. The cotton area was also marginally smaller at 12.1 million hectares. (Reporting by Mayank Bhardwaj; Editing by Kirsten Donovan)