Thesis Abstract

Abstract
Nitrogen is an essential nutrient for rice production, and its efficient management is crucial for achieving high yields in both irrigated and rain-fed rice cultivation systems. This study aimed to evaluate nitrogen management options for irrigated and rain-fed rice varieties in the Sudan Savanna of Nigeria. Field experiments were conducted to compare the effects of different nitrogen fertilizer rates and application methods on the growth, yield, and nitrogen use efficiency of rice varieties under irrigated and rain-fed conditions. Results from the study showed that nitrogen application significantly influenced the growth and yield of rice varieties in both irrigated and rain-fed systems. In the irrigated system, higher nitrogen rates resulted in increased plant height, tiller number, panicle length, and grain yield. However, excessive nitrogen application led to lodging and reduced nitrogen use efficiency. In the rain-fed system, nitrogen application also improved growth and yield parameters, but the response was less pronounced compared to the irrigated system. Different nitrogen management options, including split application and use of controlled-release fertilizers, were evaluated to improve nitrogen use efficiency and reduce environmental impacts. Split application of nitrogen fertilizer at different growth stages was found to be more effective in promoting rice growth and yield compared to a single basal application. Similarly, the use of controlled-release fertilizers improved nitrogen use efficiency by ensuring a more gradual release of nitrogen to match the crop's demand. Furthermore, the study also assessed the performance of different rice varieties under varying nitrogen management practices. The results indicated that certain rice varieties responded better to nitrogen application than others, highlighting the importance of selecting suitable varieties based on nitrogen availability and management practices. Overall, this research provides valuable insights into nitrogen management options for irrigated and rain-fed rice cultivation in the Sudan Savanna of Nigeria. The findings emphasize the importance of optimizing nitrogen fertilizer rates and application methods to enhance rice productivity while minimizing environmental risks associated with nitrogen losses. By adopting appropriate nitrogen management strategies, farmers in the region can improve rice yields sustainably and contribute to food security and economic development.

Thesis Overview

1.0 INTRODUCTION

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.