Relevance of the topic. High competitiveness of weeds in black poplar plantations is primarily due to their effective competition for nutrients, water, and partly for light. It should be taken into account that in nature, poplar grows along riverbanks and on humid lands where the number of weeds is limited. In addition, slow growth in the first year of vegetation and low density of poplar plants compared to other crops are the main factors limiting the ability of poplars to compete with weeds.
Therefore, revealing the peculiarities of weed infestation and studying the competitiveness of black poplar plantations, along with the development of effective and environmentally friendly weed control systems for the conditions of the Right Bank Forest-Steppe of Ukraine are topical issues.
The scientific novelty of the obtained results. For the first time: a comprehensive study of weed infestation of black poplar plantations in the first and subsequent years of vegetation is carried out; the competitiveness of poplar in different growing seasons is studied; a herbicide weed control system is developed; a rational system of the effective weed control in black poplar plantations during the whole vegetation period is developed.
Improved: ecological methods of weed control for black poplar plantations of the first year of vegetation that provide efficient control of weed sprouts during the growing season and do not require hand weeding.
The following issues have been further developed: scientific substantiation of weed growth and development; peculiarities of phytocenotic relationships with cultivated plants.
The practical significance of the obtained results. Based on the results of the field experiment, a scientifically sound system of weed control for black poplar plantations of the first year of vegetation has been developed. Effective protection against dicotyledonous weeds is ensured by herbicides Shtefan New, KE (phenmedipham, 160 g/l, desmedipham 160 g/l) at an application rate of 0.5 l/ha applied after the emergence of monocotyledonous species, and Shtarga, KE (quizalofop-P-ethyl, 50 g/l) at an application rate of 1.5 l/ha. The most effective environmental protection methods are shielding the soil surface with a sawdust or chopped straw layer of 10–15 cm.
The main results of the research. The most significant weed seed stock (seeds/m2) in the 0−5 cm soil layer made up Chenopodium album (11.11), Setaria glauca (10.10), and Synapsis avrensis (8.23). Moderate seed stock formed Echinochloa crus-galli (5.26), Thlaspi avrense (3.57), and Persicaria lapathifolia (3.12).
It was found that in the control treatment weeds formed 1281 g/m2 of green mass, of which dicotyledonous species 744 g/m2 and monocotyledons 537 g/m2. However, with the application of herbicides Shtarga (1.5 l/ha) and Shtefan New (0.5 l/ha), weed green mass amounted for 145 g/m2.
It was found that carrying out three cultivations between rows, as well as three harrowing between rows using mounted mesh harrows with 14-day interval reduced weed mass by 2.7 and 2.8 times, respectively. Carrying out three hand weeding between rows at a height of 1.5–3.0 cm with the same interval reduced weed mass 3.3 times, while covering the soil with a 15-cm layer of sawdust almost destroyed the weeds.
Mulching black poplar plantations using sawdust with a layer of 5, 10, and 15 cm proved to be effective in terms of high plant productivity. In this case, the treatment with a sawdust layer of 5 cm provided slightly smaller plant increment (155 cm) and, accordingly, lower dry matter yield and energy yield. However, the treatments with a 10 and 15-cm layer of sawdust did not differ significantly. The use of straw as mulch was no less effective.
Establishing poplar plantations is quite expensive in the economic aspect, and therefore the first harvest does not allow compensating for the costs of planting and plant care. Accordingly, for the three years of the experiment, we obtained not profit but economic loss.
At the same time, among the studied weed control treatments, the most effective ones appeared those with herbicides. Thus, with the combined application of Shtarga (1.5 l/ha) + Shtefan New (0.5 l/ha) herbicides, the difference in profit compared to the clean control was 6551 UAH/ha. From the environmental point of view, the best treatment was mulching with a 5-cm layer of straw that brought a profit of 4169 UAH/ha. In mechanical weed control treatment with three harrowing between rows using mounted mesh harrows, the profit was 5631 UAH/ha.
