The paper highlights the results of research carried out in the period from 2012 to 2017 dedicated to the theoretical and practical aspects of the formation of phytocoenoses of perennial bioenergy crops.
The domestic and foreign studies on the peculiarities of growing energy crops in Ukraine and abroad are analyzed. Peculiarities of weed infestation of energy willow plantations and weed control methods are described.
It was found that weed species composition of Miscanthus giganteus plantations includes 34 species, of which 5 Liliopsida and 29 Magnoliopsida. In the willow energy stands, 6 Liliopsida and 30 Magnoliopsida species were found.
The peculiarities of bioenergy crops biological potential are presented. The regional assignment data for Miscanthus giganteus and energy willow in Ukraine is presented.
In Miscanthus giganteus stands, the largest number of weeds appeared in the period from mid-May to early June, while in energy willow the period was from early May to early July. In the plantation of Miscanthus giganteus, 2906 g/m2 of green weed mass accumulated, while in willow the value was 3548.3 g/m2.
The largest seed productivity (the number of seeds per 1 plant) in Miscanthus giganteus stands was ensured by Amaranthus retroflexus (332,000) Chenopodium album (67,100), Cirsium arvense (24,000), Sonchus arvensis (21,000), Solanum nigrum (19,800) and Sinapis arvensis (15,400). The largest number of seeds per 1 plant in willow energy plantations was represented by Hyoscyamus niger (404,500), Chenopodium album (92,100), Solanum nigrum (29,400), Cirsium arvense (23,200), Sinapis arvensis (17,100), Polygonum lapathifolium (9,000) and Setaria glauca L. (5,200).
The uptake of mineral nutrients in Miscanthus giganteus plantations was as follows (kg/ha): 102.9 N, 65.7 P2O5 and 114.4 K2O. Mechanical weed control reduced these values 4.4–6.4 times, 4.3–6.1 times and 4.4–6.4 times, respectively. The uptake of mineral nutrients in energy willow stands decreased as a result of weed control: N from 127 to 45 kg/ha (64.6%); P2O5 from 87 to 32 kg/ha (63.2%) and K2O from 142 to 50 kg/ha (64.8%).
The best option of weed control for miscanthus plantations, both from an economic and energy point of view, appeared herbicide Maister Power, which ensured an operating profit of UAH 28,700 per hectare at energy yield of 436.7 GJ/ha and Kee of 9.18.
The plantations of energy willow where specially prepared cuttings were planted along with the application of soil-based herbicide Stomp in the first year demonstrated higher indicators of economic efficiency operating profit of UAH 29,700 per hectare and energy yield of 399.9 GJ/ha. However, the highest energy yield was obtained in those energy willow plots where plants were covered with a 12–15-cm layer of wheat straw in the first year of growing.
Keywords: Miscanthus giganteus, energy willow, weeds, soil herbicides, post-emergence herbicides, mulching, interrow hoeing.
