SodininkyStĖ ir darŽininkyStĖ 28(2)

investigators, neither single nor repeated weed removal in optimal period helps toavoid yield decrease (Bond, Burston, 1996). Presently herbicides are widely appliedfor weed destruction. Oxyfluorfen is very effective herbicide suitable for weed destructionin onion and cabbage crop (Stall, Gilreath, 2002).The aim of the study – to investigate the effect of Oxyfluorfen sprayed two andthree times in different rates on weeds in onion crop.Object, methods and conditions. Investigations were carried out at the LithuanianInstitute of Horticulture in 2006–2007. Soil – sandy loam on light loam, calcaricepihypogleyic luvisol (IDg 8-k, / Calc(ar)i – Epihypogleyc Luvisolls – LVg-p wcc). Ploughing layer was of 22–25 cm thickness, of little humus (1.58 %), neutral(pH KCL7.0). There was big amount of agile phosphorus (354 mg kg -1 of the soil), potassium(146 mg kg -1 of the soil) and calcium (4 500 mg kg -1 of the soil) in the soil,but small amount of nitrogen (in the layer of 0–40 cm – 56.6 kg ha -1 N-NH 4+ N-NO 3).In spring before sowing 60 kg ha -1 N, 90 kg ha -1 P, 150 kg ha -1 K were poured. Therewas grown onion cultivar ‘Babtų didieji’. Investigations were carried out according tothe mechanized technology of onion growing on flat surface created at the LithuanianInstitute of Horticulture. Onion experimental area was 216 m 2 . Total plot area was6 × 3 = 18 m 2 , and the area of record plot – 5 × 2 = 10 m 2 . Experiment was carriedout in 4 replications.Herbicides in onion crop were sprayed after sowing according to the scheme:1) control (without herbicides, weeded);2) Oxyfluorfen for three times (0.1 l ha -1 ) (for the first time when onions producedthe first leaf, for the second time – 10 days after the first spraying and for the thirdtime – 10 days after the second spraying);3) Oxyfluorfen for two times: when onions produced two leaves (0.25 l ha -1 ) andwhen onions produced three leaves (0.3 l ha -1 ).Herbicides were sprayed with back sprayer. Water rate – 400 l ha -1 . Weeds werecounted in four places of every plot, in areas of 0.25 m 2 , diagonally thought the plot,once after the month from the last spraying. After weed calculation, they were weededonce. The data of crop weediness and onion yield were calculated by dispersionanalysis method. Before carrying out statistical analysis, the number of weeds wasrecounted according to the formula: √(x + 1) (Tarakanovas, 1999).Results. In all the onion plots sprayed with herbicides the number of annual dicotyledonusweeds decreased essentially. Annual dicotyledonus weeds were averagelysensitive (70.6–71.4 %) to herbicide Oxyfluorfen spraying both three times (0.1 l ha -1 )and two times: when onions produced two leaves (0.25 l ha -1 ) and when they producedthree leaves (0.3 l ha -1 ) (Fig. 1).During the years of investigation these types of annual dicotyledonus weeds prevailedin onion crop: white goosefoot (Chenopodium album L.), scentless camomile(Matricaria inodora L.), shepherd’s purse (Capsella bursa-pastoris L.), rough amaranth(Amaranthus retroflexus L.), stinkweed (Thlaspi arvense L.) and common groundsel(Senecio vulgaris L.). Shepherd’s purse, rough amaranth and common groundselwere very sensitive to herbicide Oxyfluorfen, respectively 80.7–85.2 %, 92–94 % and84.6–90.0 %. White goosefoot and scentless camomile were averagely sensitive tothis herbicide, respectively – 72.8–74.6 % and 55–58.5 % (Fig. 2).106