1.1 BACKGROUND OF THE STUDY
Rice (Oryza sativa L.) is the main food crop of an estimated 40% of the world‟s population (Liu, 2013; FAO, 2008). The World‟s more than three billion people depend on rice as their staple food and the demand for rice is rapidly increasing in West Africa (FAO, 2003). Manypeople in the major rice consuming countries are living at sub‐optimal nutritional levels, there is need to increase rice production by as much as 70% in order to raise nutritional levels to satisfy current dietary needs (Greenland, 1997).Annually, about 5 million metric tons of rice is consumed in Nigeria and over 80% is imported costing the country a humongous amount of money (Onu et al., 2015).Local production is low and efforts to increase production are hindered by high input costs, low prices for riceespecially under rain-fed conditions.
Fertilizer nitrogen (N) has become one of the key inputs in food production and despite numerous research investigations; our understanding of N management for rice grown under diverse agro-ecological situations is still inadequate. Cereals including rice, wheat and maize, accounts for more than half of the total fertilizer N used in the world. Research has also shown that about 50 – 70 % more cereal grain will be required by 2050 to feed over 9 billion world population (Yadvinde-Singh et al., 2011) and this will further increase demand for fertilizer N at greater magnitude.