£25,000 worth of damage was caused after arsonists destroyed more than 1,000 bales of straw in Sutton Road, Haddenham.
The victim is now offering a reward of £1,000 for information leading to the arrest and conviction of the offender.
Inspector Dick Turner said: “This arson attack led to the loss of a large amount of straw with a very high value and we are keen to catch those involved.
“Crops and produce are a vital part of farming and we take the destruction of these items very seriously.
The incident happened on Monday August 15 at around 8pm.
Anyone with information should call police on 101 or Crimestoppers, anonymously, on 0800 555 111 or at www.crimestoppers-uk.org
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