Influence of site and management on the occurrence of Geranium spp. in winter oilseed rape in Germany

Julius-Kühn-Archiv

关键词: Entscheidungsbäume;    Geranium dissectum;    Geranium pusillum;    Geranium rotundifolium;    Konkurrenz;    Unkrautbekämpfung;    Unkrautmonitoring;    classification and regression trees;    competition;    weed control;    weed survey;   

DOI  :  10.5073/jka.2012.434.086

来源: DOAJ

【 摘 要 】

High intensity of oilseed rape (OSR) cropping and weeknesses in a restricted range of herbicides available for this crop favoured the spreading of problematic weeds in OSR during the last two decades.In a nationwide weed survey of OSR fields, the extent and composition of the weed infestation post herbicide application was determined. On the one hand the investigations aimed at identifying weed species that frequently occur despite herbicide application in OSR and are able to compete with the crop at late growth stages. On the other hand the survey was conducted to analyse the contribution of site properties and management factors to the spread of single problematic weed species. Between 2006 and 2008, a total of 452 fields were surveyed. At the end of OSR flowering the cover of each identified weed species was estimated across the whole field according to a five level scale. Additionally, information on site properties and management measures was collected. Median comparisons served to statistically verify preferences of Geranium pusillum, G. dissectum and G. rotundifolium regarding the investigated factors. By the use of classification and regression trees (CART), explanatory variables were weighted due to their importance to G. pusillum and G. dissectum and probabilities of occurrence due to different combinations of management factors and herbicide applications were calculated for these species.Geranium spp. were found in 46.5 % of the investigated OSR fields. All three species preferred sites with lower crop density and most frequently occurred in altitudes above 200 m and after multiple applications of herbicides that eliminated competing weeds. Furthermore the Geranium spp. showed different preferences regarding soil quality, the kind of soil tillage and the sowing date of OSR.