Stem lodging parameters of main culm and primary tiller of upland rice cultivars as affected by nitrogen fertilizer rates

Abstract

Lodging resistance (LR) assessment is usually carried out using the main culm (MC) which can be mixed- up with the primary tiller (PT), both of which can vary in morphology. Four rice cultivars namely: NERICAs 1, 4, 6 and Moroberekan were established under three rates (0, 60, 120 kg ha-1) of nitrogen fertilizer. At 20 days after heading of each of the MC and PT, the culms were harvested for LR assessment. Higher nitrogen fertilizer rates increased the outer minor diameter, stem breaking force and stem length from breaking point to panicle top of both the MC and PT. Lodging traits (LTs) varied among the rice cultivars but the rice cultivars responded similarly to application of nitrogen fertilizer in the MC unlike the inconsistencies observed in the PT. The LTs were higher in MC and with lower lodging index than in the PT. The LTs of MC and PT of Moroberekan were similar unlike differences observed between the two tillers among the NERICAs. The MC remains reliable for the assessment of LR but does not represent the general pattern of lodging in the PT of upland rice cultivars. Consistency in tiller selection is required for an unbiased assessment of lodging among upland rice cultivars.

Keywords

• lodging index, main culm, nericas, nitrogen fertilizer, primary tiller