"How to develop bigger-scale, professional farms, co-operatives, joint-stock partnerships, et cetera is a key issue, as the number of rural labourers keeps decreasing," he said.

With very limited arable land compared to its large population, the mainland's traditional agricultural system has been based on small, family-run small holdings.

Dr Cheng Guoqiang, secretary general of the DRC's academic committee, said at a forum in Beijing this month that innovations in the system of agricultural production might be the new focus of agricultural policies.

"China used to have a huge number of farmers, and this group of people is now migrating [to urban areas] at a pace of 15 million to 20 million a year," he said. "In the future we will see at least 100 million residents move out of rural areas."

Professor Zheng Fengtian, from Renmin University's school of agricultural economics and rural development, said developing specialised, commercialised, vertically integrated, large-scale agricultural production was urgently needed because farm produce prices had become more volatile in recent years and farmers lacked professional organisations to lead them.

"The document could emphasise this issue, but of course, like those issued in past years, will also cover other problems related to rural development," he said.

Then-party general secretary Hu Jintao's report to the party's national congress last month proposed to "foster new types of agricultural business entities, and develop large-scale agricultural operations in diverse forms".

At a Politburo meeting early this month, the party's new leadership pledged to "increase investment in agricultural science and technology, and encourage the development of new patterns of agricultural production and management".

A State Council meeting at the end of last month said effective measures should be introduced to encourage some rural youth to stay in the countryside so that a steady workforce could be built up to push ahead with agricultural modernisation.

The exodus of workers has left only the elderly and children behind in most rural areas, and that has become a concern, with many saying that it will make it hard to implement large-scale, mechanised farming.

Tian Yihui, who graduated from Shandong Agricultural University and now works for an agricultural technology company in Beijing, said very few of his schoolmates chose to work in rural areas after graduation. "A fifth of them found jobs that had nothing to do with agriculture," he said. "Some became civil servants, and most work in companies related to agriculture in urban areas."

Xu said that on his field research trips he had found that most farms in rural areas measured less than 20 mu (1.3 hectares) - too small to be an attractive work option for young people. "I believe young people would be willing to stay if they could have a farm as large as 100 mu," he said.

Rural farmland that was owned by collectives has been divided into separate plots and parcelled out to households. That has been an obstacle for large-scale farming because plots rented from different households can be far apart.

Xu said the party's traditional focus on rural issues in its first policy document of the year showed that policymakers attached great importance to them.

"The point is to guide fiscal spending, bank loans and private capital to the agricultural sector," he said.

Mainland media have reported that while the authorities might support diverse forms of agricultural production in next year's No1 document, they were also likely to suggest imposing limits on commercial capital in rural areas.

Cheng warned at the forum that commercial capital was targeting land for investment.