Growth and productivity of poplar nursery plantations under different heights of cutting shoots

Abstract

Purpose. To develop major agrotechnical measures for growing the maximum number of one-year lignified poplar cuttings for the establishment of energy plantations in the conditions of the Right Bank Forest Steppe of Ukraine. Methods. Field, laboratory, statistical. Results. Nursery plantings of three poplar varieties were studied: one-year plantation of variety 'Dorskamp' and three-year plantations of varieties 'Robusta' and 'I-45/51'. At this age in the spring of 2019, the plants were cut at a height of 0.00, 0.25, 0.50 and 1.00 m from the ground surface. Plants of 'Dorskamp' variety that were cut at 0.00 m grew to a height of 2.27±0.124 m for 1 year, at 0.25 m to 2.85±0.135 m and at 0.50 m to 2.81±0.143 m. In the subsequent years, after cutting, the height of plants of 'Dorskamp' variety increased as follows: in 2020 to 3.01±0.231 m, 3.22±0.170 m and 3.30±0.170 m; in 2021, to 3.53±0.230 m, 4.11±0.129 m and 3.85±0.188 m, respectively. 'Robusta' variety in the first year after cutting had the highest average height indicators that decreased with each subsequent year (except for the height of 100 cm). One-year shoots of 'I-45/51' variety were the highest in 2020. In 2021, they had the maximum height indicators of the three varieties, 4.50±0.165 m. The yield of cuttings from 1 ha of the nursery plantation of 'Dorskamp' variety in 2019 varied from 166.6 thousand shoots/ha for cutting at a height of 0.25 m to 184.9 thousand shoots/ha at a height of 0.00 m. In the following 2 years, the yield of cuttings increased both with the increase in the age of the plantation and the cutting height. In the third year (2021), 'Dorskamp' had the maximum indicators, 397.2 thousand shoots/ha at a cutting height of 0.25 m. In 'Robusta' variety, already in the next year after the first cutting, the yield of cuttings ranged from 942.5 to 2621.3 thousand shoots/ha. At the same time, the yield increased significantly with an increase in cutting height and in most cases decreased in subsequent years. In 'I-45/51' variety, the yield of standard shoots in the first year after cutting increased with an increase in cutting height from 105.8−101.3 thousand shoots/ha to 200.6 thousand shoots/ha (at a height of 1.0 m). In 2020, it was from 128.2 thousand shoots/ha to 226.0 thousand shoots/ha, respectively, for cutting at 0.00 m and 1.00 m. In 2021, the yield of shoots in the variants 0.00 m and 0.50 m slightly decreased, and for cutting at heights of 0.25 and 1.00 m increased to 134.3 and 265.5 thousand shoots/ha, respectively. Conclusions. The productivity of poplar nursery plantations in the conditions of the research region is largely affected by the varietal characteristics, the age of the plants, and the weather conditions of a certain year. Among the varieties used in the study, the maximum yield of standard planting material (shoots) is noted in nursery plantations of 'Robusta', amounting to 2.6 million shoots/ha. 'I-45/51' variety had much lower productivity, up to 0.26 million shoots/ha. The plantation of 'Dorskamp' variety, 2 years younger than 'Robusta' and 'I‑45/51', had a yield of shoots per hectare up to 0.40 million. The highest yield of planting material in most cases was ensured by the cutting at 0.50–1.00 m.