New Concepts on Soil Fertility and Plant Nutrition As Illustrated by Research on Forest Trees and Stands

The interrelationships and use of a series of general concepts in modelling plant nutrition and growth are exemplified with laboratory and field experiments with steady state nutrition and growth mainly of forest tree species. It follows from mathematical derivations that in order to maintain a constant nutrient concentration in the plant, the relative uptake rate, RU, and therefore the relative addition rate, RA, must equal the relative growth rate, RG. A concept corresponding to RA has been introduced to specify the rate of nutrient supply under field conditions, the nutrient flux density, Dn. The ability of the plant to take up the nutrients made available is expressed in the concept of utilization capacity, Un. The experimental results suggest that plant nutrient requirements can be defined by two variables: complete nutrient proportions in plant and fertilizer and rate of application of fertilizer to support current growth.