MINERAL FERTILIZERS’ AFTER-EFFECT ON SOIL PROPERTIES AND STAND PRODUCTIVITY IN A LONG-TERM EXPERIMENT IN KARELIAN MIDDLE TAIGA

Abstract

The after-effect of long-term application of various doses and combinations of mineral fertilizers (NPK, N) to pine crops on sandy Al-Fe-humus podzolized podbur soils was studied in the middle taiga of Karelia, near Lake Rindozero. The pine crops established by seeding in 1962 were fertilized in 1970, 1975, 1979 and 1985. The setup was N, NPK, and control (not fertilized). By the time of the survey the sample plots were occupied by 53‑year-old pure pine stands. Thirty years after the last treatment, 10 replications of forest floor samples were taken from each 0.5 ha plot to determine the stock, and 3 soil pits were made in each plot to take samples from specific genetic horizons for chemical analysis. In the sample plots, the most significant changes compared to the control were observed in the forest floor and the underlying eluvial horizon. The productivity of the resultant pine stands was promoted considerably, especially by NPK fertilization. Statistical treatment of the data revealed a significant increase in the forest floor stock upon fertilization in all the treatments as compared to the control. Mean tree diameter and height, as well as the stands’ growing stock were enlarged.

Keywords

• pine crops
• after-effect
• long-term fertilization
• podburs
• forest floor
• productivity