Crop rotation influence on the weed incidence in cereals

Analysis of the crop rotation influence on the weed incidence in cereals is based on monitoring of crops during 1997-2007 in Kurzeme and Zemgale regions of Latvia. The Department of Soil Management (currently the Institute of Soil and Plant Sciences) of Latvia University of Agriculture has been studying the dynamics of weed level in fixed annually observed areas. The type of crop rotation was selected by a land holder. The weed infestation was determined using the quantitative occurrence method developed by A. Rasinsh and M. Taurina /Rasins, Taurina, 1989/. The support of this method is a correlation between the incidence of weed species in the field and the number of weed species per m(2) of field area. The incidence of weeds was studied in four types of crop rotation in 2007: cereals grown in a crop rotation; repeated cereal sowings; cereals during five years without exchange and winter wheat during 4-5 years. Significance of crop rotation for weed control systems was certified by comparison of weed species incidence in fields.