Smallholders and and rural households should be helped, the FAO said
Food production will have to increase by 70% over the next 40 years to feed the world's growing population, the United Nations food agency predicts.
The Food and Agricultural Organisation says if more land is not used for food production now, 370 million people could be facing famine by 2050.
The world population is expected to increase from the current 6.7 billion to 9.1 billion by mid-century.
Climate change, involving floods and droughts, will affect food production.
The FAO said net investments of $83bn (£52.5bn) a year - an increase of 50% - had to be made in agriculture in developing countries if there was to be enough food by 2050.
"The combined effect of population growth, strong income growth and urbanisation... is expected to result in almost the doubling of demand for food, feed and fibre," FAO Director-General Jacques Diouf told delegates at a forum entitled How to Feed the World 2050.
The FAO said that even if governments increased agricultural investments, there could still be 370 million people suffering from famine in 2050.
Difficulties ahead included a scarcity of natural resources such as land, water and biodiversity.
Food production would also have to deal with "the effects of climate change, notably higher temperatures, greater rainfall variability and more frequent extreme weather events such as floods and droughts," Mr Diouf warned.
Climate change would reduce water availability and lead to an increase in plant and animal pests and diseases, he said.
Mr Diouf said it was important to increase food production in areas where it was most needed, as climate change could reduce potential output by up to 30% in Africa and up to 21% in Asia.
"There should be a special focus on smallholder farmers, women and rural households and their access to land, water and high quality seeds... and other modern inputs," he said.
He added that the biofuel market also presented competition to food production.
Biofuel production is set to increase by nearly 90% over the next 10 years to reach 192 billion litres by 2018, the FAO said.