The species composition of weeds in lentil crops during the years of research was mixed and was represented by plants of both annual and perennial dicotyledonous and monocotyledonous species. In the period before harvesting (mid-July), the most numerous plants were the following (plants/m2): Solanum nigrum 5.0 (12.4 % in the structure of weeds), Avena fatua 4.8 (11.9), Chenopodium album 4.4 (10.9 %), Amaranthus retroflexus 3.5 (8.7 %), and Echinochloa crus-galli 3.5 (8.7 %).
The largest amounts of the weed vegetative mass in crops without weed control measures were formed during the period of lentil beans maturation (mid-July), 2359 g/m2 (841.5 g/m2 of dry matter). The largest share in the weed mass structure had Amaranthus retroflexus (429.7 g/m2; 18.2 %), Chenopodium album (404.8 g/m2; 17.2 %), Solanum nigrum (207.6 g/m2; 8.8 %), and Setaria glauca (184.5 g/m2; 7.8 %).
Under the structure of the weed infestation in the experiment, the various weeds removed from the soil approximately 98.7 kg/ha of nitrogen compounds, 62.8 kg/ha of phosphorus and 110.0 kg/ha of potassium. The largest uptake values showed Chenopodium album, Solanum nigrum, Amaranthus retroflexus, and Setaria glauca.
Application of pre-emergent herbicides Hezaguard 500 SC, Zenkor 70 WG, and Stomp 330 EC together with graminicide herbicides Panther 4 % EC, Targa Super 5 % CE and Fusilade Forte 15 % ensured a reduction in weed number from 48.3 to 60.2 % and in weed mass from 56.8 to 80.5 %.
The yield of lentil seeds in the plots where crops were maintained clear of weeds over the years of the research averaged 1.73 t/ha, while in the control plot (no weed control) it was only 0.18 t/ha. Accordingly, yield loss due to the presence of weeds reached 1.55 t/ha, that is 89.6 %. The best treatments of herbicidal crop protection appeared Zenkor 70 WG (0.6 kg/ha) + Targa Super (1.25 L/ha) and Stomp 330 (3.0 L/ha) + Fusilade Forte (0.6 L/ha) that provided seed yield of 1.45 and 1.40 t/ha, respectively, or 83.8 and 81.0 % of the maximum seed yield in the experiment.
Maximum application rate of Zenkor 70 WG (0.7 kg/ha) and Stomp 330 EC (4.0 L/ha) induced chemical stress in lentil plants, which was manifested in the delay of the growth processes and development of juvenile plants by 4–7 days, and, as a consequence, reduce the seed yield by 0.14 t/ha ( 9.7 %).
The highest rates of cost-effectiveness of growing lentils were obtained when using herbicide Zenkor 70 WG (0.6 kg/ha) + Targa Super EC (1.0 L/ha) and Hezaguard 500 SC (3.0 L/ha) + Panther 4 % EC (1.0 L/ha). In particular, the turnout from the sale of products (seeds) in these treatments s amounted to 22.8 and 23.4 thousand UAH, with net profit of 13.7 and 14.3 thousand UAH, and the profitability of 151.9 and 157.1 %, respectively. The largest values of the energy efficiency coefficient in these treatments were 1.29 and 1.31, respectively.
Keywords: weeds; weed infestation processes; lentill; control; herbicides.
