Growth of seedlings of Agropyron repens (L.) Beauv. and Agrostis gigantea Roth in cereal crops

Experiments were undertaken to define the conditions under which seeds and seedlings of Agropyron repens and Agrostis gigantea may start infestations in cereal crops. When seedlings were planted early or late in spring wheat and spring barley, most growth of shoots and rhizomes was produced by Agropyron planted early in wheat. Late planting halved the amount of shoot growth and severely inhibited rhizome formation. In winter wheat given a moderate or zero amount of nitrogen fertilizer in spring, growth of the weed seedlings was slow. Rhizomes were not produced during the time the crop was growing but only after harvest. Agrostis made more growth than Agropyron in most treatments throughout most of the experiment. Late planting decreased growth more than in the spring cereals. Nitrogen fertilizer, although it had little effect on the amount of growth made by winter wheat, increased the growth of the early-planted seedlings but decreased that of the late-planted ones of both weed species. When planted into plots given nitrogen, more seedlings of both species died after late than after early planting. Clearly, the amount of growth and rhizome produced by seedlings of these two species will depend on the type of cereal, the time of emergence of the seedlings in relation to the cereal, and on other factors affecting the relative vigour of cereal and weed. Evidently, where the weed seedlings emerge early in weakly or moderately competitive cereal crops or when growth is unchecked in the cereal stubble, seedlings could give rise to infestations.