Cambridgeshire Police and Cambridgeshire Fire and Rescue Service believe all the fires, near Peterborough, were started deliberately.
The quick-thinking actions of firefighters and farmers ensured the fires were controlled before they were able to spread.
Farmer Judith Jacobs said it is lucky the impact was not severe and farm fires are a major ongoing concern.
Lives and wildlife at risk
The third-generation beef farmer and NFU member said: “Sadly, we experienced similar incidents several times last summer, and this kind of behaviour is completely unacceptable.
“With the current hot and dry weather, these fires pose a serious risk. They could easily spread to nearby homes, farmland and standing crops, putting lives, livelihoods and wildlife at risk.
“They also place unnecessary pressure on our fire service, wasting valuable time, resources and water at a time when they are already extremely busy.”
At around 8pm on Sunday 28 June, six fires were seen at different locations around the fields and hedgerows at Moor Farm, between Peakirk and Glinton.
Farmers Jake Bedlow and Oscar Priestly rushed out with buckets of water to get the fires under control before firefighters arrived.
Then at around 10.30pm on Monday 29 June a derelict caravan full of tyres was set alight in a lay-by on Gunthorpe Road, near the Barn Garden Centre, close to Moor Farm.
Mrs Jacobs said: “We saw the fire and immediately called the fire service and the police.
“This was extremely dangerous. Burning tyres also release thick, toxic smoke and harmful pollutants into the air, posing a risk to public health and contaminating the surrounding environment.”
Reward for information
Mrs Jacobs thanked the firefighters for their swift response and is offering a reward to anyone who provides information which leads to the people responsible being identified.
She said: “If you have CCTV footage, witnessed any suspicious activity, or have any information that could help, please get in touch.
“By looking out for one another, we can help keep our community safe and protect our countryside.”
'Farm fires can be devastating'
A Cambridgeshire Fire and Rescue Service spokesperson said: “One of our biggest risks at this time of year is fires on farmland.
“This is because of several factors, such as fire spreading quickly across dry land, securing an adequate water supply and accessing the correct location.
“Farms are particularly vulnerable to deliberate fires and arson due to their isolated location, open boundaries, readily ignitable hay and straw stacks often making them easy targets.
“Any fire, no matter how small, can quickly get out of control, endangering those around and the fire crews that come to tackle it. Farm fires can be devastating.”
Anyone with information should contact Cambridgeshire Police by visiting www.cambs.police.uk to submit an online report or call Crimestoppers, anonymously, on 0800 555111.