The effect of nitrogen fertilization and foliar application of fertilizers on yield and energy efficiency of giant miscanthus plantations

Purpose. To improve the technology of caring for giant miscanthus plantations and establish the features of its productivity formation with the use of different types of fertilizers, starting from the second year of crop vegetation. 
Methods. The research was carried out in the years 2020–2021 in the Bila Tserkva Experimental and Breeding Station of the Institute of Bioenergy Crops and Sugar Beet of the National Academy of Agrarian Sciences of Ukraine, which is located in the zone of unstable moisture of the Right Bank Forest Steppe of Ukraine. The design of the experiment included application of mineral fertilizers [ammonium nitrate + ammonium sulfate (N24 + S6 kg/ha a.i.), ammonium nitrate (N24 kg/ha a.i.)] in a row zone in spring, foliar application of humates (Vermisol, 8.0 l/ha, Humifield BP-18, 0.4 l/ha) and complex fertilizer with amino acids (Quantum Aminomax, 0.5 l/ha). Mineral fertilizers were applied before the emergence of miscanthus sprouts; foliar application of fertilizers was carried out in the 5-leaf stage and the second time after two weeks. 
Results. Giant miscanthus plants in second year of vegetation formed from 18 to 37 shoots with an average weight of 76.3 to 111.0 g, with the maximum weight of one plant reaching 4091 g. In the next year of research, the number of stems per plant and their average weight increased by 1.5–2 times, and the maximum weight of one plant was 7016 g. Biomass yield of giant miscanthus in the third year of vegetation was 31.0–74.6 t/ha, the estimated yield of solid biofuel was 19.2–41.6 t/ha and energy 315.5–683.2 GJ/ha. 
Conclusions. Application of mineral fertilizers (ammonium nitrate + ammonium sulfate, ammonium nitrate) in spring contributed to significant increase in the indicators of raw biomass yield, solid biofuel output, and energy yield per hectare. Foliar application of Humifield BP-18 has a significant positive effect on the productivity of giant miscanthus. The best indicators of crop productivity were obtained in treatments combining spring fertilization with ammonium nitrate and ammonium sulfate (N24 + S6) followed by two-time foliar application of humates (Vermisol, 8.0 l/ha, Humifield BP-18, 0.4 l/ha) and complex fertilizer with amino acids Quantum Aminomax, 0.5 l/ha.