Influence of Container Volume and Cuttings Size on Growth Parameters of Seedlings with Closed Root System of Two Poplar Genotypes in the Voronezh Region

The article deals with the bioproductivity of 2 poplar genotypes propagated by single-tree stem cuttings. The experiment compared variants using cuttings of different lengths (10-22 cm) and containers with volumes from 1 to 3 litres. The experiment also considered the variant grown using the Pot-in-pot technology. It was found that the best growth performance of seedlings in height according to the traditional container technology (70.6±5.5-111.5±5.0 cm) was observed in the intersectional hybrid of poplar ‘E.s.-38’ (genotype 1). Annual seedlings of black poplar (genotype 2) were inferior in this index (53.7±4.8-68.1±7.8 cm). PiP technology in case of both genotypes showed good results of height gain (genotype 1 - 165±10.3 cm, genotype 2 - 73.3±8.6 cm). The predominance of the factor ‘Genotype’ over the technology of rooting cuttings (selection of the length of the initial material and the volume of the growing container) was established. In terms of total biomass, G1 (54.4 g) on average exceeds G2 (9.9 g) (natural species) (by 5.5 times), which is determined by a reliable difference in height (by 1.74 times), in diameter by 1.7 times. For both genotypes, depending on the cultivation variant, we can distinguish productivity groups based on the total dry weight of plants: high-productive groups: for G1 - 3L18cm; 3L14cm; 2L22cm; PiP, for G2 - PiP; 3L22cm; 3L18cm, low-productive groups: for G1 - 2L10cm; 1L10cm; 1L14cm, for G2 - 3L14cm; 3L10cm; 2L14cm; 2L10cm; 1L14cm; 1L10cm. The fast-growing genotype 1 ʻE.s.-38ʼ has high productivity and plant height indices, which allows it to be recommended as a variety allowing to grow standard planting material in containers in one season. For genotype 1, the length of cuttings can be 10-14 cm when the container volume is increased to 3 litres, which will increase the number of cuttings from one mother plant by 2-3 times. For genotype 1, the use of containers with a volume of 2 or more litres will produce planting material with a height of more than 100 cm and a diameter of 8-10 mm. Planting material of hard-to-cut poplar species and varieties should be grown in containers with the volume of at least 2 litres. The optimum length of cuttings is 22 cm. Application of Pot-in-pot technology will increase the height of containerised seedlings of fast-growing poplar genotypes by 47 %, diameter by 60 %, and in case of hard-to-propagate genotypes it will increase the height by 20 %, diameter by 20.3 %, which agrees with the data of researches obtained in nurseries of different countries.