Environment Secretary Owen Paterson said the UK should be "proud" of the "fantastic" job farmers do.
He will hold a summit today to discuss the financial worries of many farmers after a year of bad weather.
He added: "This last year has been particularly tough. Farming contributes a huge amount to our environment and our economy.
"We want to ensure that farmers are able to deal with challenges like bad weather, to grow their businesses, create new jobs and help the country compete in the global race."
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The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.
Four people have died and the suspect is still at large, police said.