Updated

Leaders of the Bill & Melinda Gates Foundation say it could be 20 years before they see results from their massive anti-poverty effort in Africa.

The world's largest charitable foundation has committed $1.7 billion to help African farmers boost their income and feed hungry people.

It's investing millions in seed research, buying and distributing fertilizer and improving farmers' education and access to markets. It's also trying to persuade governments to spend more money on agriculture and to improve trade and land ownership policies.

But the foundation's deputy director of global development, Roy Steiner, says agricultural development happens slowly and it could take "years and years" to fully measure the progress.

Steiner says the long-term goal to prevent food crises by strengthening agricultural systems.