Genotypic differences in grain yield and nitrogen uptake of lowland rice (Oryza sativa L.) under two production systems and levels of nitrogen / Mark Joshua Sombilon Quevedo

Thesis (Master of Science in Agronomy) -- Visayas State University, December 2018

Nitrogen fertilization and irrigation greatly contribute to improve rice yield. Excessive N application may cause harm to the environment, incur additional production cost and lower N use efficiency. With changing climate, water availability may limit rice production. This study was conducted to determine the agronomic, yield and physiological performance of inbred and hybrid rice under System of Rice Intensification (SRl) and conventional production system; to evaluate the Internal Nitrogen Use Efficiency (INUE) of these rice varieties under two production systems; and to evaluate the profitability of growing inbred and hybrid rice under these production systems. The experiment was laid out in a nested design following a randomized complete block design with two varieties as main plots (inbred and hybrid) and levels of N as subplot
(0 kg N ha'and 90 kg N ha') under two production systems (SRI and conventional). Inbred rice grown under SRI headed earlier than hybrid rice in similar condition and both varieties under the conventional production system. Irrespective of production system, hybrid variety and those applied with N were taller than inbred and without N application. Regardless of variety and levels of N applied, lowland rice grown under SRI had more productive tillers, filled spikelets, heavier 1,000 grains, higher root pulling resistance (RPR) and leaf area index (LAI). Grain yield is higher when 90 kg of N is applied in any production system than without N. Inbred variety produced significantly higher grain yield similar to hybrid variety when applied with 90 kg N ha· '. Application of90 kg N ha' gave higher INUE under SRI comparable to conventional without N application. Water use in SRI was reduced by 32% than in conventional production system. Highest gross margin was attained by inbred rice applied with 90 kg N ha grown under SRI than in conventional production system.