Skip to main content Accessibility help

Competition Effects on Yield, Tissue Nitrogen, and Germination of Winter Wheat (Triticum aestivum) and Italian Ryegrass (Lolium multiflorum)

  • Abul Hashem (a1), Steve R. Radosevich (a1) and Richard Dick (a2)


Field experiments were conducted to study the competition effect of winter wheat planted in a square arrangement and Italian ryegrass planted randomly on biomass yields of both species, ryegrass seed yield, N use efficiency, and progeny seed germination. Increases in wheat density up to 800 plants/m2 reduced ryegrass seed yield by 87% but increased its harvest index up to 42% compared to its monoculture yield. Species densities and their interactions accounted for 66 to 73% of the total variation in per-unit area biomass of species, and their association was more favorable to ryegrass biomass than wheat. Seeds of each species had three times greater nitrogen percentage than did shoots. Intra- and interspecific competition increased nitrogen percentage in wheat seeds. In Italian ryegrass, only interspecific competition increased N percentage in seeds. Although total nitrogen uptake by winter wheat was three times greater than in Italian ryegrass, Italian ryegrass was two times more efficient than wheat at producing biomass per unit of N taken up and specific leaf area at heading stage in mixture. Germination percentages of progeny seeds of both species in mixtures were greater in presence of high densities of the companion species than in their monocultures. Nitrogen was not the main limiting factor for competition between winter wheat and Italian ryegrass in this study.


Corresponding author

Corresponding author's E-mail:


Hide All
Ampong-Nyarko, K. and De Datta, S. K. 1993. Effect of nitrogen application on growth, nitrogen use efficiency and rice-weed competition. Weed Res. 33: 269276.
Angonin, C., Caussanel, J. P., and Meynard, J. M. 1996. Competition between winter wheat and Veronica hederiifolia: influence of weed density and the amount and timing of N application. Weed Res. 36: 175187.
Appleby, A. P., Olson, P. O., and Colbert, D. R. 1976. Winter wheat yield reduction from interference by Italian ryegrass. Agron. J. 68: 463466.
Bremner, J. M. and Mulvaney, C. S. 1982. N-Total. In Page, A. L., Miller, R. H., and Keeney, , eds. Methods of Soil Analysis. Agronomy No. 9 Part 2. pp. 595625.
Burrill, L. C., Braunworth, W. S. Jr., William, R. D., Parker, R. R., Swan, D. G., and Kidder, D. W. 1988. Pacific Northwest Handbook. Corvallis, Or: Oregon State University agricultural communication. pp. 2948.
Chapin, F. S. III. 1980. The mineral nutrition of wild plants. Ann. Rev. Ecol. Arrang. 11: 233260.
Concannon, J. A. 1987. The effect of density and proportion of spring wheat and Lolium multiform L. . Oregon State University, Corvallis, OR. 101 p.
Gill, G. S. and Blacklow, W. M. 1984. Effect of great brome (Bromus diandrus) on the growth of wheat and great brome and their uptake of N and phosphorus. Aust. J. Agric. Res. 35: 18.
Grundy, A. C., Frond-Williams, R. J., and Boatman, N. D. 1993. The use of cultivar, crop seed rate and nitrogen level for the suppression of weeds in winter wheat. In Proceedings of the Brighton Crop Protection Conference—Weeds, Brighton. Brighton, UK: British Crop Protection Council. pp. 9971002.
Hashem, A., Radosevich, S. R., and Roush, M. L. 1998. Effect of proximity factors on competition between winter wheat (Triticum aestivum) and Italian ryegrass (Lolium multiflorum). Weed Sci. 46: 181190.
Iqbal, J. and Wright, D. 1997. Effects of nitrogen supply on competition between wheat and three annual weed species. Weed Res. 37: 391400.
Lemerle, D., Verbeek, B. R., and Coombees, N. E. 1995. Losses in grain yield of winter crops from Lolium rigidum . Weed Res. 35: 503509.
Liebl, R. and Worsham, A. D. 1987. Interference of Italian ryegrass (Lolium multiflorum) in wheat (Triticum rigidum). Weed Sci. 35: 819823.
Mason, M. 1987. Effect of agronomic practices on wheat protein levels. J. Agric. West. Aust. 28: 128130.
Mason, M. G. and Madin, R. W. 1996. Effect of weeds and N fertiliser on yield and grain protein percentage of wheat. Aust. J. Exp. Agric. 36: 443450.
Poorter, H. 1989. Interspecific variation in relative growth rate: on the ecological and physiological consequences. In Limbers, H., Cambridge, M. L., Conings, H., and Pons, T. L., eds. Causes and Consequences of Variation in Growth Rate and Productivity of Higher Plants. The Hague, The Netherlands: SPB Academic. pp. 4568.
Radosevich, S. R. 1987. Methods to study interaction among crops and weed. Weed Technol. 1: 190198.
Radosevich, S. R. 1988. Methods to study crop and weed interaction. In Alteiri, M. A. and Leibman, M., eds. Weed Management in Agroecosystems: Logical Approaches. Boca Raton, FL: CRC Press. pp. 121143.
[SAS] Statistical Analysis Systems. 1987. SAS/STAT Guide for Personal Computers. Version 6 ed. Cary, NC: Statistical Analysis Systems Institute.
Spitters, C.J.T. 1983. An alternative approach to the analysis of mixed cropping experiment. I. Estimation of competition effects. Neth. J. Agric. Sci. 31: 111.
Tanji, A. and Zimdahl, R. L. 1997. The competitive ability of wheat (Triticum aestivum) compared to rigid ryegrass (Lolium rigidum) and cowcockle (Vaccaria hispanica). Weed Sci. 45: 481487.
Wilson, B. J., Peters, N.C.B., Wright, K. J., and Atkins, H. A. 1988. The influence of crop competition on the seed production of Lamium purpureum, Viola arvensis, and Papever rhoeas in winter wheat. Asp. Appl. Biol. 18: 7180.
Wilson, B. J., Wright, K. J., Brain, P., Clements, M., and Stephens, E. 1995. Predicting competitive effects of weed and crop density on weed biomass, weed production and crop yield in wheat. Weed Res. 35: 265278.
Zadoks, J. C., Chang, T. T., and Konzak, C. F. 1974. A decimal code for the growth stage of cereals. Weed Res. 14: 415421.



Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed