Nigeria's, the world's eighth biggest crude producer, relies heavily on oil income which accounts for some 80% of its total revenue.
A budget specialist in the ministry, Bright Okogu, said oil and gas revenue is projected to fall 34% in 2009.
The ministry said the money earmarked for civil servants' travel, training, vehicles and meals has been reduced.
President Umaru Yar'Adua has sought a reduction in salaries and allowances of political office holders, a move he says is not just "symbolic" but essential to "ensure that we live within our means, especially in these critical times".
Finance Minister Mansur Muhtar said the 2009 budget tries to widen the base for non-oil taxes and focuses on growth-enhancing expenditure.
Yar'Adua said while signing the budget that Nigeria's oil output has dropped to 1.6 million barrels per day compared with around 2 million barrels per day last year.