Police believe thieves could be deliberately targeting farmers in Lincolnshire.
On Monday night a tractor was taken from Sutton Bridge and another from Sutton St James.
A total of 17 have been stolen from across the county in the past month, with four taken from a farm in Wrangle overnight between Friday and Saturday.
Philip Odling, from the Spilsby Branch of the National Farmers Union, said the thefts were having a huge impact.
Mr Odling said tractors played a "vital role" in the industry at this time of year.
"When a tractor is stolen it means that they can't carry on planting, drilling, sowing, whatever," he added.
Lincolnshire Police have urged people in rural areas to remain vigilant to suspicious activity.