SAO PAULO, Nov 13 (Reuters) - A "super soybean harvest" is ruled out for the 2020/2021 season in Brazil's biggest grain state, Mato Grosso, as irregular rains cast doubt over yields and the volumes when the crop is ready next year, an analyst with agribusiness consultancy AgRural said on Friday.

The Brazilian government said earlier in the week that Mato Grosso will reap almost 37 million tonnes of soybeans in 2021, while Brazil should harvest a record of about 135 million tonnes.

"A bumper crop is out of the question," AgRural analyst Fernando Muraro said about Mato Grosso, declining to elaborate.

He said growers are having to replant seeds in areas such as Campo Novo do Parecis and Diamantino, in the west of the state.

In the traditional producing towns along the BR-163 highway, in the middle north portion of Mato Grosso, the climate situation is a little better after a recently downpour, Muraro said.

"It is a completely atypical year," Muraro said about the state expected to supply almost 30% of Brazil's soybeans in the season. "It is unusually dry in Mato Grosso, and this is historical."

A drought in September led to planting delays in some regions of Brazil and in Mato Grosso, where sowing has covered 94% of the estimated area, according to Imea, the privately-owned Mato Grosso research agency.

On Friday, listed agricultural firm Terra Santa Agro told investors climate uncertainty led it to reduce the total area to be planted with grains and oilseeds this season, to 130,200 hectares (321,731 acres) from 149,500 hectares.

Planting is way behind in the north of Paraná state, Muraro said after personally surveying fields in Brazil's second-biggest soy producer. (Reporting by Roberto Samora in São Paulo Writing by Ana Mano Editing by Marguerita Choy)