Interference of Italian Ryegrass (Lolium multiflorum) in Wheat (Triticum aestivum)

Abstract

Wheat (Triticum aestivumL.) grain yields were reduced an average of 4.2% for every 10 Italian ryegrass [Lolium multiflorum(Lam.) # LOLMU] plants/m2within the range of 0 to 100 Italian ryegrass plants/m2. Yield reductions caused by Italian ryegrass were attributed primarily to decreased crop tillering. Italian ryegrass densities as high as 80 plants/m2had little effect on wheat head or kernel weights. In greenhouse experiments, the growth response of Italian ryegrass to increasing concentrations of NO3–and K+was greater than that of wheat. Net uptake rates for NO3–by both species growing in nutrient solution were 1.5 times greater than net uptake rates for K+. Nitrate and potassium Imaxvalues for Italian ryegrass were approximately twice the corresponding values for wheat. Although Italian ryegrass responded more to changes in nutrients and had greater ion uptake rates compared to wheat, Italian ryegrass accumulated more biomass when grown in monoculture than when grown in association with wheat. This difference was probably due to the initial size of the seedlings. Wheat seedlings were much larger than Italian ryegrass seedlings during the first 20 days following emergence.