According to official data, as many as a third of farmers in northeastern Jilin, Liaoning and Heilongjiang provinces have insufficient agricultural inputs after authorities sealed off villages to fight the pandemic. The three provinces account for more than 20 per cent of China’s grain production.

A drop in the output of Chinese spring-planted grains, such as rice or corn, could undermine Beijing’s decades-long effort to achieve self-sufficiency in staple foods, forcing it to increase imports and potentially adding to global food price inflation.

While national and global attention has been focused on Shanghai’s lockdown of its entire population over the past week, Jilin province has been battling an outbreak with even stricter measures for most of the past month.

According to the Jilin provincial government, about one-third of farmers did not have enough fertiliser at the end of March — only about three weeks before they were supposed to begin planting.

Farmers and factory managers have blamed the disruption on China’s uncompromising zero-Covid policy, under which authorities have adopted tough controls ranging from traffic bans to local business shutdowns.

A Beijing-based adviser to the central government on agriculture policies said China risked “facing food shortages”.

“We have to adjust the zero-Covid policy for farming,” said the adviser, who asked not to be named. “We shouldn’t prioritize virus control over everything else. This can’t carry on forever.”

The municipal government of Jilin city, located within Jilin province, said preparations for the spring planting season were proving to be very difficult. “We are behind [schedule] in making fertilizer available to every farmer,” it said in a statement posted on its website.

Li Qinghua, a 38-year-old farmer who grows rice on 60 acres of land in Jilin city, said his fertiliser inventory was more than 80 percent below normal levels after delivery was delayed. “I will miss the best time window to plant seeds if my order doesn’t arrive next week,” said Li.

China’s agriculture ministry did not immediately respond to a request for comment made on Tuesday, a public holiday.