The influence of different periods of weediness on yield and quality of field beans in Eastern Croatia

Field experiments with different periods of weediness in field bean (cv. 'S lavonski zeleni') were initiated in 1998 at two localities in Osijek-Baranj a county, Republic of Croatia. The objective was to investigate susceptibil ity of the beans to competition at different stages of crop growth in order to assess the feasibility of using alternatives to prophylactic pre-emerge nce sprays. The natural weed vegetation was allowed to develop for differen t periods and mainly comprised Sorghum halepense, Cirsium arvense, Lathyrus tuberosus, Chenopodium album and Setaria glauca. Yields and yield componen ts (pods/plant, seeds/pod, 100 kernel weights and plant height) were assess ed. When weeds were present throughout the growing season, there was almost complete loss of yield (95%). If, however, weeds only remained for the fir st 2-3 weeks after crop emergence, final yield and yield components were un affected. If present for longer than this, the yield was reduced significan tly and progressively. The serious effects of weeds in reducing yield were associated with an initial competitive disadvantage of the crop - due to it s slower germination and growth, since about 20-50 % of weeds had emerged b efore the bean. Alternative control strategies which may both reduce total herbicide inputs and also avoid the need for prophylactic pre-emergence spr ays are discussed.