Segatalinės floros pokyčiai Lietuvoje paskutiniaisiais dešimtmečiais

Abstract

Piktžolių flora Lietuvos pasėliuose labai pasikeitė per pastaruosius dešimtmečius. Piktžolėtumo kontrolė cheminėmis priemonėmis ir kitos priežastys sąlygojo tai, kad sumažėjo dviskilčių, bet išplito vienaskiltės piktžolės, ypač dirvinė smilguolė (Apera spica – venti). Šių piktžolių plitimą skatino sėjomainos nebuvimas, ankstyva žieminių javų sėja bei nearimis dirvos dirbimas. Atsiranda ir kitų anksčiau problemų nekėlusių piktžolių. Ūkininkų apklausa parodė, kad ateityje žieminiai rapsai gali kelti rūpesčių kaip nepageidaujami augalai kitų augalų, ypač vasarinių rapsų pasėliuose

Weeds are a permanent component of agro- ecosystems and remain the most important factor causing yield reduction. Efficient and timely weed control is one of the major tasks of competitive, intensive contemporary agriculture. Public concern about the effects of herbicide use on the environment and human health has increased the interest in reducing the use of herbicides in agriculture and in developing alternative methods for weed control. Efficient weed control can be achieved only with a good knowledge of weed occurrence, harmfulness, population dynamics. Weed flora is affected by the changes in crop rotation, fertilization, management strategies and use of herbicides. Herbicides seem to be one of the major factors determining changes in weed flora. In Lithuania, weed surveys were conducted during the periods 1957 – 1961, 1980 –1984 and were completed between July and August, just before harvest in spring and winter cereals. Fields were managed conventionally – tilled and sprayed with herbicides. In 2010, a short expedition to the main cereal growing regions was arranged and a farmers’ survey on the changes in weed populations over the last decades was carried out. To clarify the problem of new agricultural crops’ weed incidence we enclosed some questions about spring and winter rape in the questionnaire. The first weed survey showed that agricultural crop fields were heavily weed- infested. In winter cereals, the number of annual and perennial weeds ranged from 348 to 609 m-2 and from 291 to 591 m-2 in spring cereals. Especially high incidence was of mono- and dicotyledonous perennial weeds, which accounted for about half of the total number of weeds. A second survey made in 1984 revealed that weed incidence in cereal crops substantially (by 60 – 80%) decreased. An especially considerable decrease was observed for perennial weeds. [...]