Competition between red sprangletop (Leptochloa chinensis) and rice (Oryza sativa) under different nitrogen levels.

摘要

A study on the competition between red sprangletop (Leptochloa chinensis) and rice under different nitrogen levels was conducted under greenhouse conditions from August 1994 to March 1995. The results showed that rice plant height and tiller numberwere reduced by red sprangletop. The effects were more pronounced after treatment with nitrogen fertilizer 30 days after seeding. Chlorophyll contents of rice leaves were relatively high when treated with nitrogen fertilizer. Rice panicle numbers were significantly reduced by competition with red sprangletop, but increased with increasing nitrogen levels. Higher percentages of filled grain were obtained where competition by red sprangletop occurred or under high nitrogen rates. A significant reduction in rice grain yield due to red sprangletop competition was obtained, being consistent, irrespective of nitrogen level (39-48%). No correlation was found between percentage yield loss and increase in nitrogen levels. The reduction in the concn of nitrogendue to red sprangletop competition ranged from 0.03 to 0.13 g/plant (4.0-21 kg N/ha).