- Fernandez, Ivan Joseph
University of Maine Graduate School
An experiment was designed to test the effects of potassium fertilization of a loamy sand and a loam textured forest soil on the growth jack pine (Pinus bankisana Lamb.) seedlings. A greenhouse experiment involving 7 levels of potassium on 2 forest soils with 4 replications was designed with 0, 28, 56, 112, 224, 448, and 896 kg K/ha. All experimental units received 112 kg/ha N, 448 kg/ha P, 2240 kg/ha Ca and 560 kg/ha Mg. The seedlings were grown for 8 months with 14 hours of light per day. Distilled water was added daily by weight, to maintain a water tension of 0.1 bar.
Dry weight yield of seedlings grown on the loam was significantly greater than those grown on loamy sand. While there were no significant dry weight increases attributable to the potassium additions, there was visual evidence that the potassium additions did improve growth. The greatest numerical dry weight yields were associated with potassium concentrations of 0.44 to 0.61 percent in the seedling.
Increasing potassium treatments caused an increase in the concentrations of calcium and magnesium in both soil solution and tissue. There was some evidence for an initial depression in uptake of the divalent cations with lower levels of potassium. Characterization of potassium uptake was highly dependent on concentrations of and competition from calcium, magnesium, and aluminum in the soil solution.
The ion exchange selectivity of the soils studied was variable with the loamy sand being much more selective for potassium, as compared to calcium, than the loam. Both soils substantially increased in selectivity for potassium with increasing potassium concentrations.
The quadratic correlation coefficients for polynomial regression analyses were used to determine the best fitting intensity function form both soils. Regression analyses were run for selective for selected forms of the intensity function and both exchangeable soil potassium (q) and percent of potassium in the seedling tissue. These correlation coefficients were averaged for each intensity function and the form yielding the highest correlation coefficient was chosen as the best suited intensity function for that soil.