CHAPTER ONE

1.0 INTRODUCTION

Rice (Oryza sativa L.) is an important staple for more than half of the world’s population. It

accounts for 18.99% of calorie, 1.83% of fat and 12.73% of protein intake per day (FAOSTAT,

2011). The demand for rice may increase by 60% by 2025 (Fageria et al., 2003). The demand for

rice is growing particularly in sub-Saharan Africa due to rapid population growth, consumer

preference and rising income. Nigeria is the largest consumer of rice in sub-Saharan Africa with

an estimated demand of 6.7 million metric tons of milled rice (USDA, 2017). Production is

estimated at 3.8 million metric tons of milled rice and has failed to keep pace with the growing

demand resulting to the importation of 2.6 million metric tons of milled rice to fill the gap.

(USDA, 2017).

Low yield has been identified as major constraint to rice production in Nigeria where average

yield is estimated at 1.88 tons per hectare (USDA, 2017). Soil nutrient depletion and low

fertilizer use have been commonly cited as yield limiting factors in Nigeria (Ezui et al., 2010;

Liverpool-Tasie et al., 2014). Farmers understand the need to apply nutrients to their land but

little is used due to the economic and social factors surrounding access to fertilizer. High cost

and delayed delivery of fertilizer are major limitations to its use in rice production. The expenses

incurred in procuring fertilizer in Sub-Saharan Africa are two to six times the cost in Europe or

the United States (Sanchez, 2002). Cost of importation, market inefficiencies and transportation

cost are some of the factors responsible for high fertilizer prices. Excessively high fertilizer cost

usually reduces the profitability of fertilizer use (Kaizzi et al., 2012a).

Several studies have reported significant increase in yield of rice with fertilizer application.

Ishaya and Dauda (2010) reported optimum yield of 7 tons/ha with application of 130 kg/ha of

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nitrogen in the sudan savanna. Kamara et al. (2011) observed yield increase of 3 tons/ha with the

application of 100kg/ha of N to NERICA varieties. In a trial conducted by Jibrin et al. (2010) in

the sudan savanna, 120kg/ha of N increased yield by 62.9%.

1.1 Statement of Problem

The Fertilizer recommendation for all irrigated lowland rice in Nigeria has been 100 kg/ha N,

60kg/ha P2O5 and 60kg/ha K2O (Chude et al., 2011) with the assumption that the need for

applied nutrients is constant over varieties, seasons and diverse agro-ecological zones. Fertilizer

recommendations are commonly developed without considering the cost of fertilizer relative to

the price of paddy typically referred to as fertilizer cost to paddy price ratio (CP). Instead, the

fertilizer rates needed to attain maximum yield have often been estimated. The CP is an indicator

of how much of an output is required to purchase a kilogram of a nutrient (Liverpool-Tasie et al.,

2014). As the fertilizer cost increases relative to price of paddy, the Economically Optimum Rate

(EOR), described as the nutrient rate needed to maximize net return to fertilizer use, is expected

to decrease (Wortmann et al., 2007). In Nigeria, Liverpool-Tasie et al. (2014) observed that the

CP can be as low as 1.7 and high as 11.2 in some years and farming systems. Applying fertilizer

at existing recommendations when the CP is high could lead to low net returns on fertilizer use.

Kaizzi et al. (2012a) and Kaizzi et al. (2014) developed regression equations to relate CP and

EOR for maize and rice respectively. This provided a means for estimating EOR at any CP

value.

In addition, Nitrogen is the most limiting nutrient in rice production as it is prone to losses by

volatilization, leaching and denitrification (Wortmann et al.,