Factors Explaining Differences in Yield Response to High Nitrogen Fertilization among Rice Varieties under Tropical Highland Conditions in Central Kenya

Japan Agricultural Research Quarterly
ISSN 00213551
NII recode ID (NCID) AA0068709X
Full text
A decrease in the filled grain ratio (FGR) under high nitrogen (N) conditions inhibits the increase in rice yield in the tropical highlands of equatorial East Africa. We hypothesized that, under high N fertilization, the decrease in FGR is due to low temperatures during the reproductive growth stages, and that high grain yield can be achieved using cold tolerant varieties. Two cold-susceptible varieties (BW196 and Komboka) and a cold-tolerant variety (NERICA 1) were grown under 57, 114, and 171 kg N ha−1 of N fertilization. Grain yield increased with a higher N fertilization rate only in NERICA 1. Shoot dry weight and total spikelet number increased in all varieties under high N conditions. Although FGR decreased with increases in N fertilization rate in all varieties, the adverse effects of high N fertilization on FGR were least observed in NERICA 1. However, temperature did not affect FGR in all N treatments, growth stages, and varieties, except for Komboka during the ripening stage under high N conditions. The findings did not support the hypothesis that high-N-induced decreases in FGR are due to low temperatures. High-N-induced decreases in FGR in Komboka were mainly attributable to the poor filling of spikelets during the ripening stage due to excess total spikelets. Factors other than filling high-N-promoted increases in total spikelet number may affect FGR in BW196 and NERICA 1 under high N conditions in Mwea.
Date of issued
Creator Hiroaki SAMEJIMA Keisuke KATSURA Mayumi KIKUTA Symon Mugo NJINJU John Munji KIMANI Akira YAMAUCHI Daigo MAKIHARA
Subject East Africa grain yield filled grain ratio low temperature lowland rice
Publisher Japan International Research Center for Agricultural Sciences
Received Date 2020-03-10
Accepted Date 2020-09-18
Volume 55
Issue 3
spage 209
epage 216
DOI https://doi.org/10.6090/jarq.55.209
Language eng

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