Varietal variations of lowland rice in response to N-urea rates: implications on nitrogen use efficiency and crop performance in a derived savanna

Abstract

Low N-urea rate increased nitrogen use efficiency and grain yield in lowland rice. The questions remain what constitutes low N-urea rate in a derived Savanna and to what extent would there be differential response of these traits in interspecific varieties of lowland rice. Field experiments were conducted in the inland valley, Federal University of Agriculture, Abeokuta, (Latitudes 7° 15'N, Longitude 3° 25'E, altitude 144 above sea level) in 2020 and 2021 to determine the performance of interspecific lowland rice cultivars at low rates of N-urea. Application rates of N-urea (0, 30 and 60 kg N ha−1) were applied on lowland rice cultivars (ARICA 3, NERICA L-34, WITA-4 and Ofada cv.) that constituted the main plot and sub plot, respectively. The Experiments were in split plot arrangement fitted into randomized complete block design and replicated three times. Increased N uptake and delayed phenology were observed with increasing application rates of N-urea, while grain yield of lowland rice sown at 30 and 60 kg N ha−1 were similar. NERICA L-34 had significantly higher Partial Factor Productivity of N (PFPN) and Nitrogen Harvest Index with higher sink strength than other cultivars. Similar pattern was observed on grain yield. These evidences suggested that application of 30 kg N ha−1 could sustain the reproductive growth of lowland rice because of prolonged phenology and N uptake in a derived Savanna with higher efficiency (PFPN, Agronomic efficiency N and Recovery efficiency N) despite the similarities in their root growth and activities.