Nigeria is facing a possible food supply crisis this farming season, traders say, as the agricultural sector grapples with a predicted shorter rainy season, sectarian violence and greater demand from Niger.

Food experts have raised the alarm after the country's meteorological agency said this year's rainy season could be shorter than usual, compounding a likely fall in production due to insecurity.

Nigeria's agricultural sector is heavily dependent on the rains, with the bulk of its produce cultivated in the north and central region.

But this year, weather forecasters said the rains, which normally come in May, could start a month later and dry up before September, curtailing the planting and cropping season.

"All these factors put together are a great source of concern on possible food shortage at the end of the rainy season and the lean period when food stocks are usually depleted," said Ya'u Tumfafi, from the Dawanau Grains market in the northern city of Kano.

Dawanau is reputed to be the largest grain market in West Africa and supplies not only other parts of Nigeria but also Niger, Chad, Cameroon and Mali.

Traders typically comb towns and villages in northern and central Nigerian states at harvest, sourcing grains and tubers from farmers which are then brought to the market for sale.

- Violence hitting crop yields -

The fears over supply have also been stoked by the Islamist insurgency in northern Nigeria, which has claimed thousands of lives and forced farmers to abandon their land since it began in 2009.

The United Nations estimates that, up until January 1, some 300,000 people had been displaced in the northeastern states of Borno, Yobe and Adamawa since a state of emergency was imposed in May.

A further 65,000 people have fled Borno and Adamawa since the turn of the year, Nigeria's emergency response agency NEMA has said.

Residents in remote villages, who depend on agriculture for their livelihoods, have either left for fear of further attacks or depleted all their food stocks.

Borno state's agriculture ministry believes farms are unlikely to be re-populated any time soon, which will hit this year's crop season.

Last year, for example, 5,000 hectares (12,355 acres) of wheat and rice were left to rot in the Marte area of Borno near Lake Chad after 19,000 farmers abandoned their farms.

"We lost 200 metric tonnes of wheat as a result of the exodus," said Abubakar Gabra Iliya, head of the Lake Chad Basin Development Agency, based in the Borno state capital, Maiduguri.

A 2012 NEMA report said that violence linked to the Boko Haram insurgency has caused 60 percent of farmers to leave the fertile region.

At Dawanau market, the supply of sorghum (cereals), sesame, beans and millet -- all staple crops grown in the northeast -- has fallen by 35 percent, said grain trader Tumfafi.

Last year, a bumper harvest of beans and sorghum from southern parts of Katsina state made up the shortfall.

But there are fears this year that renewed sectarian violence in the area, as well as in the central state of Nasarawa and Benue, in the east, will cut yields.

- Restore peace, increase aid -

In the last three years, demand for grain from Niger to the north has increased due to drought-induced food shortages.

The government in Niamey said in November that about one million people were facing severe food shortages due to poor harvests and required assistance.

As a result, traders in Kano say their counterparts from across the border have been frantically snapping up stocks.

"Grain demand from Niger has put serious strain on stock availability here and with the disturbing prospect of low yield this crop season, it will put further strain on available stock after harvest, said Aminu Mohammed, from the Dawanau traders union.

The Nigerian Meteorological Agency has advised farmers to use early maturing seeds for the shorter crop season.

But Mohammed said donor agencies needed to increase food aid to Niger at the same time to ease the pressure on supplies from Nigeria.

"Seeds, no matter how sophisticated, have to be planted by humans to germinate," added Ibrahim Mota, from the Dawanau grain traders union.

"The immediate restoration of peace in violence-torn parts of the north to allow displaced farmers to return to their homes and cultivate their farms is the best guarantee to good harvests".