Income from farming in Buckinghamshire fell to a record low last year, figures show.
The National Farmers' Union said 2020 was a challenging year for the industry, with farms across England losing over £1 billion in revenue.
Figures from the Department for Environment, Food and Rural Affairs show the total income from farming in Buckinghamshire was estimated to be around £22.8 million in 2020.
This was a real-terms fall of 40 per cent from 2019, when income was £37.8 million, and the lowest figure since comparable records began in 2010.
In the South East and London, farming income decreased by 31 per cent to £360.3 million last year, making it the fifth most affected of the seven English regions.
Across England, total income within the agriculture industry fell to £2.6 billion in 2020 – a drop of £1.1 billion when adjusted for inflation.
The NFU said the figures show the "significant disruption" caused by Covid-19.
A spokesman for the union added: "Many farms lost their entire market overnight, particularly those who supplied the out-of-home market at home or abroad, and saw prices fall due to lower demand.
"Many farm businesses who had diversified, for example by owning a B&B or hosting other leisure activities, found those closed due to restrictions.
"This disruption, alongside rising input costs and ongoing labour challenges, made 2020 a significantly challenging year and highlights the volatility farmers face year-on-year."
The value of crop output from farms across England fell to £7.6 billion in 2020 – the lowest level since 2007.
In Buckinghamshire, it dropped from £68.4 million in 2019 to £50.1 million last year.
Meanwhile the total output from livestock across the region also fell from £87.5 million to £82.1 million over this time.
The Farming Community Network, a charity that supports farming families through difficult times, said it will be a challenge for some businesses to stay profitable.
Mark Thomas, head of services at the FCN, said: “Many farm businesses, such as those operating holiday accommodation, have seen a loss of income due to Covid-19.
"This is in addition to the stresses caused by the everyday pressures involved in farming which are often out of farmers’ control, such as adverse weather.
"Farmers benefit from support from consumers, respecting the countryside and farmers’ land, buying locally sourced, high-quality food and taking advantage of the leisure and tourism opportunities rural Britain has on offer."
He added that with the phasing out of the Basic Payment Scheme – the biggest of the rural grants that helps the farming industry – in the coming years, farmers need clarity from government on how future policy could affect business.
A Defra spokesman said: “One year into implementing our new agricultural policy we have made great progress in working with farmers to design a better system for farm payments which incentivises farmers to farm more sustainably, creates space for nature and enhances animal welfare outcomes."