Recovery of nitrogen fertilizer by traditional and improved rice cultivars in the Bhutan Highlands

Bhim Bahadur Ghaley, Henning Høgh Jensen, Jørgen Lindskrog Christiansen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The recovery of soil derived nitrogen (NDFS) and fertilizer N (NDFF) was investigated in highland rice (Oryza sativa L.) fields in Bhutan, characterized by high inputs of farmyard manure (FYM). The effect of 60 kg N ha−1 (60 N) applied in two splits to a traditional and an improved cultivar, popular among the farmers, was investigated using the 15N isotope dilution technique. No differences were found between cultivars with respect to the uptake of NDFS and NDFF, but the improved cultivar yielded 27% more (P ≤ 0.05) grain compared with the traditional cultivar. This was largely due to its greater harvest index (HI). The mean percentage recovery of fertilizer N (REN) applied at 45 days after transplanting (DAT) was 34% compared to 22% at 7 DAT, resulting in 56% greater uptake of NDFF at 45 DAT. The overall REN for both the improved and the traditional cultivars were 25.7% and 30% respectively, with no difference between cultivars, but REN decreased with increasing FYM inputs. Fertilizer N recommendations that allow for previous FYM inputs combined with applications timed to coincide with maximum crop demand (45 DAT), and the use of improved cultivars, could enhance N fertilizer recoveries (REN) and increase rice yields in the Bhutan Highlands.
Original languageEnglish
JournalPlant and Soil
Volume332
Issue number2-2
Pages (from-to)233-246
ISSN0032-079X
DOIs
Publication statusPublished - 2010
Externally publishedYes

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