SOIL CHEMICAL LIMITATIONS TO GROWTH AND DEVELOPMENT OF VERONICA-OFFICINALIS L AND CAREX-PILULIFERA L

Veronica officinalis and Carer pilulifera, widespread plants of acid s oils in Europe, were grown in 50 soils of natural and seminatural ecos ystems representing a wide range of soil chemical properties. The expe riment was performed in a greenhouse at a soil moisture content of 55 - 65% WHC, ca. 60% R.H. of the air, temperature 14-16 degrees C at nig ht and 19-21 degrees C by day; additional light 70 W m(-2) 12 h d(-1). Properties closely related to soil acidity precluded growth of V. off icinalis and limited the growth rate of C. pilulifera at soil pH-KCl < ca. 3.4. In slightly moderately alkaline (calcareous) soils, growth w as primarily limited by insufficient phosphate uptake. A low growth ra te of C. pilulifera. in such soils was related to low concentrations o f exchangeable soil phosphate and low tissue concentrations of phospho rus. However, in high-pH soils, secondary effects due to suboptimum tr ace element (probably Fe) conditions, giving rise to symptoms of chlor osis, were also indicated. The highest growth rates of both species we re invariably measured in soils of intermediate acidity having very hi gh concentrations of exchangeable phosphate. Multiple regression tests on the entire material indicated that 65 - 75% of the variability in several growth functions could be accounted for, when two or more soil characters were included in the equation. Besides phosphate, exchange able Zn (in C. pilulifera) and nitrate (in V. officinalis) were of con siderable importance in accounting for growth rates.