Forming yielding capacity of green and dry mass of topinambur depending on its harvesting time

The article presents the research results on the influence of topinambur harvesting time on the green mass and absolute dry matter yields. The one-factor experiment has been launched according to the method of B.A. Dospekhov in the educational and scientific experimental field of Perm State Agrarian and Technological University. The experiment has followed the following scheme: 1 - gathering of green mass on the 10th day after the flowering phase, 2 - gathering of green mass on the 20th day after the flowering phase, 3 - gathering of green mass before tuber lifting. According to the research results, the harvesting time of green mass has not had any influence on its yielding capacity (13.1-15.5 t/ha), or the dry mass yield (3.01-3.44 t/ha). There is a tendency for the green mass yield to decrease from an earlier harvest period to a later one - by 1.7-2.4 t/ha and dry mass-by 0.16-0.43 t/ha. The plant survival rate (88-92%) and the plant standing density (3.2-3.4 pcs/m2) before harvesting have not shown any dependence on the harvesting time. A significant increase in absolute dry matter content of the crop continues until the flowering phase and reaches its maximum of 6.45 t/ha. Due to the outflow of nutrients from the aboveground part of the plant to the ground one, there is a sharp decrease in dry mass yield by the first harvest time (by 3.28 t/ha) after the flowering phase. The maximum height of plants is also found in the flowering phase -153 cm, after which the plant stops to grow. The highest vitamin C content in topinambur green mass has been found when mowing it before tuber lifting (65.6 mg/kg), the highest carotene content has been observed when harvesting the green mass on the 10th-20th day after the flowering phase (17.2-18.0 mg/kg), the highest crude ash content has been found when harvesting on the 20th day after the flowering phase (3.4%).