WEEDS of lattucE (Lactuca sativa l. SubSp. secaLina) in organic agriculturE

NikoLich, L., D. Dzigurski, B. LjevNaich-Masich, r. caBiLovski and M. MaNojLovich, 2011. Weeds of lattuce (sativa L. subsp. Secalina ) in organic agriculture. Bulg. J. Agric. Sci., 17: 736-743 The paper reviews the weed flora that develops during the organic production of lettuce, with the objective of establishing differences in weed infestation among different variants of lettuce production (non-woven agro textile mulch , straw mulch, cultivation, no cultivation - control; all previous variants were tested with and without fertilization). Weed range was estimated during the vegetation period of lettuce 2009-2010. general weed infestation rate was the highest in the control variant with organic fertilizers application (28.9 individuals/m 2 ), and the lowest in the variant without fertilization with cultivation (7.1 individuals/m 2 ). Lettuce plants were best developed in the variant with cover cloth and fertilization, while the weakest plants were registered in the variants with straw mulch. The total of 23 weed species was found in the examined variants, of which 5 were segetal weeds, 17 weed-ruderal and only one ruderal plant. Four weed species, which were also, most numerous, were present in all production variants: Bilderdykia convolvulus (L.) Dum., Datura stramonium L., Hibiscus trionum L., Polygonum lapathifolium L., Sinapis arvensis L., Solanum nigrum L. and Sorghum halepense (L.) Pers. Most of the registered species start flowering in June, which is favourable with regard to weed control, before their fructification, as it coincides with the end of lettuce vegetation. Analysis of the biological spectrum of the weed flora in all examined variants indicates the dominance of therophytes, which account for 82.61% (19 species) of the total flora.