1.1 Background to the study
Rice is a plant that produces an edible grain; the name is also used for the grain itself. There are several thousand varieties of rice (mostly wild), all belonging to the family Poaceae, formerly Gramineae (Microsoftt Student, 2007 DVD). The cultivated rice plant, African and Asian rice (oryza glaberrima L and oryza sativa L), is an annual grass. It grows to about 1.2 m (4 feet) in height. The leaves are long and flattened, and its panicle, or inflorescence, is made up of spikelets bearing flowers that produce the fruit, or grain (Rashid-Noah, 2003, & Encyclopaedia Britannica Deluxe, 2004). In Nigeria rice is planted from April to May and harvested from August to November.
Water resource management and utilization is critical to the success or failure of many agricultural enterprises especially rice farming (Hoffman and Ashwell, 2001 and World Bank, 2006). Shortle and Griffin (2001) noted that surface water (e.g. rivers, lakes, estuaries and wetlands) which are highly limited in supply provide about 70% water used in agricultural production. However, Botkin and Keller (1997) asserted that improved or efficient rice irrigation system could contribute meaningfully to meeting the desirable goals of environmental resource conservation. They held that improved irrigation systems could reduce withdrawal of freshwater by between 20% and 30%.