SAO PAULO, Dec 6 (Reuters) - The planting of Brazil's 2021/22 soybean crop had reached 94% of the estimated area as of Thursday and is progressing well in most of the country, although a recent lack of rains has put farmers on alert in some southern states, agribusiness consultancy AgRural said on Monday.

According to AgRural, national planting was up 4 percentage points from the previous week and remains ahead of the 90% that was planted at the same juncture in 2020/21.

Fieldwork in southern states such as Rio Grande do Sul and Santa Catarina, however, is being affected by drought, it said, adding that the states of Mato Grosso do Sul and Sao Paulo face the risk of potential losses due to the drier weather.

Rains came in below the historical average in November, and forecasts for the first half of December are also pessimistic in these states, AgRural said.

Because of the weather, Brazil's 2021/22 summer corn crop is expected to be below initial forecasts, AgRural analyst Daniele Siqueira told Reuters in an email. The consultancy will revise corn output data this week, she said

AgRural currently projects a total corn crop of 115.5 million tonnes, with 21.66 million tonnes being summer corn that is produced in the country's center-south states.

Despite concerns about dry weather in some areas, Brazilian soybean farmers are expected to start harvesting their crop earlier this year, as sowing began sooner in the season.

AgRural said soybean harvesting is expected to begin around Christmas in some areas in Mato Grosso, referring to Brazil's top soybean-growing state. The consultancy currently sees Brazil's 2021/22 soybean crop reaching 144.3 million tonnes. (Reporting by Gabriel Araujo and Roberto Samora in São Paulo Writing by Ana Mano Editing by Paul Simao)