Effect of sowing density on performance and biometric features of pedunculate oak

Abstract

Sowing density is one of the most important factors influencing seedling quality. In forest nurseries, to ensure full seeding, it is recommended to obtain approximately 200 seedlings from 1 m² (ZHL 2012). The aim of the study was to assess the effect of sowing density on sowing efficiency and the morphological features of pedunculate oak seedlings. Acorns were sown directly by broadcast seeding on 20 test plots, each 4 m in length, in four replications. The following variants were used:
- 250 acorns capable of germination totaling 341 acorns per 1 linear meter (0.9 m²);
- 300 acorns capable of germination totaling 410 acorns per 1 linear meter (0.9 m²);
- 350 acorns capable of germination totaling 478 acorns per 1 linear meter (0.9 m²);
- 400 acorns capable of germination totaling 546 acorns per 1 linear meter (0.9 m²);
- 450 acorns capable of germination totaling 614 acorns per 1 linear meter (0.9 m²).

At the end of the growing season, seedlings were counted per 1 m (0.9 m²) in the central part of each plot. Sowing efficiency was determined as a percentage of seedling yield from the sown seeds. For laboratory analysis, 30 seedlings from each plot (600 in total) were collected. Based on biometric features like shoot height, root collar diameter, and dry weights of shoots, roots, and leaves, quality indicators such as the sturdiness quotient (SQ) and the Dickson quality index (DQI) were calculated.

Sowing efficiency at the end of the vegetation season ranged between 39.68% and 50.12% and was not statistically significant. The research revealed that sowing density influenced seedling biometric characteristics. Pearson’s correlation coefficients showed significant negative correlations between the number of seedlings obtained in an experimental plot and the dry weight of the root, number and dry mass of leaves, as well as the DQI. The seedlings from all sowing variants complied with the binding Polish standard, outlined in the Regulation of the Minister for the Environment of 18 February 2004 (Ministerstwo Środowiska 2004) by over 96%.

Keywords: seeding density, sowing rate, seedling quality, sowing performance, sturdiness quotient (SQ), Dickson quality index (DQI), Quercus robur L.