Published online by Cambridge University Press: 20 January 2017
Junglerice is one of the world's most problematic C4 grass weedspresent in dry-seeded rice in many countries. A screenhouse study wasconducted to determine the effect of four rice planting densities (0, 100,200, and 400 plants m−2) and four nitrogen (N) rates (0, 50, 100,and 150 kg ha−1) on the growth and morphological plasticity ofjunglerice. Junglerice plant height was reduced by 15 to 35%, tiller numberby 54 to 77%, leaf number by 61 to 85%, leaf area by 69 to 90%, leaf biomassby 63 to 88%, stem biomass by 70 to 92%, and inflorescence biomass by 66 to94% at rice planting densities ranging from 100 to 400 plants m−2relative to the junglerice plants grown alone. However, all these growthparameters increased with increasing N rates. Junglerice biomass increasedby 125 to 472%, whereas rice biomass increased by 122 to 285% with theapplication of 50 to 150 kg N ha−1. Additional N favoredjunglerice biomass production relative to rice. Rice crop interference (200to 400 plants m−2) reduced junglerice growth and biomass andovershaded the junglerice plants when no N was applied. Increasing Napplication resulted in taller plants and higher biomass of junglerice,while it reduced root-shoot weight ratio. These results suggest thatincreasing N rate increased the competitive ability of the junglerice overrice regardless of crop planting density. Information generated in thisstudy could be useful in devising appropriate combinations of plantingdensity and fertilizer management strategies for cultural junglericemanagement, particularly in situations where junglerice species are moreresponsive than rice to N.
Current address: Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Toowoomba 4350, Queensland, Australia.